The Mental Life of Monkeys and Apes: A Study of Ideational Behavior

 ROBERT M. YERKES Harvard University

 BEHAVIOR MONOGRAPHS Volume 3, Number 1, 1916 Serial Number 12 Edited by JOHN B. WATSON The Johns Hopkins University

WITH SIX PLATES AND FIVE TEXT FIGURES

CONTENTS

 I. Interests, opportunity and materials

 II. Observational problems and methods

 III. Results of multiple-choice experiments:

 1. Skirrl, _Pithecus irus_ 2. Sobke, _Pithecus rhesus_ 3. Julius, _Pongo pygmaeus_

 IV. Results of supplementary tests of ideational behavior:

 1. Julius, _Pongo pygmaeus_: Box stacking experiment Box and pole experiment Draw-in experiment Lock and key test 2. Skirrl, _Pithecus irus_: Box stacking experiment Box and pole experiment Draw-in experiment Hammer and nail test Other activities 3. Sobke, _Pithecus rhesus_: Box stacking experiment Draw-in experiment Box and pole experiment Other activities

 V. Miscellaneous observations:

 1. Right- and left-handedness 2. Instinct and emotion: Maternal instinct Fear Sympathy

 VI. Historical and critical discussion of ideational behavior in monkeys and apes:

 1. Evidences of ideation in monkeys 2. Evidences of ideation in apes

 VII. Provision for the study of the primates and especially the monkeys and anthropoid apes

VIII. Bibliography

I

INTERESTS, OPPORTUNITY AND MATERIALS

Two strong interests come to expression in this report: the one in thestudy of the adaptive or ideational behavior of the monkeys and theapes; and the other in adequate and permanent provision for the thoroughstudy of all aspects of the lives of these animals. The values of theseinterests and of the tasks which they have led me to undertake are sowidely recognized by biologists that I need not pause to justify ordefine them. I shall, instead, attempt to make a contribution of fact onthe score of each interest. 

While recognizing that the task of prospecting for an anthropoid orprimate station may in its outcome prove incomparably more important forthe biological and sociological sciences and for human welfare than myexperimental study of ideational behavior, I give the latter first placein this report, reserving for the concluding section an account of thesituation regarding our knowledge of the monkeys, apes, and otherprimates, and a description of a plan and program for the thorough-goingand long continued study of these organisms in a permanent station orresearch institute. 

In 1915, a long desired opportunity came to me to devote myselfundividedly to tasks which I have designated above as "prospecting" foran anthropoid station and experimenting with monkeys and apes. First ofall, the interruption of my academic duties by sabbatical leave gave mefree time. But in addition to this freedom for research, I neededanimals and equipment. These, too, happily, were most satisfactorilyprovided, as I shall now describe. 

When in 1913, while already myself engaged in seeking the establishmentof an anthropoid station, I heard of the founding of such an institutionat Orotava, Tenerife, the Canary Islands, I immediately made inquiriesof the founder of the station, Doctor Max Rothmann of Berlin, concerninghis plans (Rothmann, 1912). [1] As a result of our correspondence, I wasinvited to visit and make use of the facilities of the Orotava stationand to consider with its founder the possibility of coöperative workinstead of the establishing of an American station. This invitation Igratefully accepted with the expectation of spending the greater part ofthe year 1915 on the island of Tenerife. But the outbreak of the warrendered my plan impracticable, while at the same time destroying allreasonable ground for hope of profitable coöperation with the Germans inthe study of the anthropoids. In August, 1915, Doctor Rothmann died. Presumably, the station still exists at Orotava in the interests ofcertain psychological and physiological research. So far as I know, there are as yet no published reports of studies made at this station. It seems from every point of view desirable that American psychologistsshould, without regard to this initial attempt of the Germans to providefor anthropoid research, further the establishment of a well equippedAmerican station for the study not only of the anthropoid apes but ofall of the lower primates. 

[Footnote 1: See bibliography at end of report. ]

In the early months of the war while I was making every effort to obtainreliable information concerning conditions in the Canary Islands, Ireceived an urgent invitation from my friend and former student, DoctorG. V. Hamilton, to make use of his collection of animals and laboratoryat Montecito, California, during my leave of absence from Harvard. Thisinvitation I most gladly accepted, and in February, 1915, I establishedmyself in Santa Barbara, in convenient proximity to Doctor Hamilton'sprivate laboratory where for more than six months I was able to workuninterruptedly under nearly ideal conditions. 

Doctor Hamilton without reserve placed at my disposal his entirecollection of animals, laboratory, and equipment, provided innumerableconveniences for my work, and in addition, bore the entire expense of myinvestigation. I cannot adequately thank him for his kindness nor makesatisfactory acknowledgment here of his generous aid. Thanks to hissympathetic interest and to the courtesy of the McCormick family onwhose estate the laboratory was located, my work was done under whollydelightful conditions, and with assistance from Ramon Jimenez and FrankVan Den Bergh, Jr. , which was invaluable. The former aided me mostintelligently in the care of the animals and the construction ofapparatus; and the latter, especially, was of very real service inconnection with many of my experiments. 

The collection of animals which Doctor Hamilton placed at my disposalconsisted of ten monkeys and one orang utan. The monkeys representedeither _Pithecus rhesus_ Audebert (_Macacus rhesus_), _Pithecus irus_ F. Cuvier (_Macacus cynomolgos_), or the hybrid of these two species(Elliot, 1913). There were two eunuchs, five males, and three females. All were thoroughly acclimated, having lived in Montecito either frombirth or for several years. The orang utan was a young specimen of_Pongo pygmaeus_ Hoppius obtained from a San Francisco dealer inOctober, 1914 for my use. His age at that time, as judged by his sizeand the presence of milk teeth, was not more than five years. So far asI could discover, he was a perfectly normal, healthy, and activeindividual. On June 10, 1915, his weight was thirty-four pounds, hisheight thirty-two inches, and his chest girt twenty-three inches. OnAugust 18 of the same year, the three measurements were thirty-six andone-half pounds, thirty-three inches, and twenty-five inches. 

For the major portion of my experimental work, only three of the elevenanimals were used. A growing male, _P. Rhesus_ monkey, known as Sobke; amature male, _P. Irus_, called Skirrl; and the young orang utan, whichhad been named Julius. Plates I and II present these three subjects ofmy experiments in characteristically interesting attitudes. In plate I, figure 1, Julius appears immediately behind the laboratory seated on arock, against a background of live oaks. This figure gives one anexcellent idea of the immediate environment of the laboratory. Figure 2of the same plate is a portrait of Julius taken in the latter part ofAugust. By reason of the heavy growth of hair, he appeared considerablyolder as well as larger at this time than when the photograph for figure1 was taken. In plate II, figure 3, Julius is shown in the woods in theattitude of reaching for a banana, while in figure 4 of the same platehe is represented as walking upright in one of the cages. 

Likenesses of Sobke are presented in figures 5 and 6 of plate II. In thelatter of these figures he is shown stretching his mouth, apparentlyyawning but actually preparing for an attack on another monkey behindthe wire screen. Figure 7 of this plate indicates Skirrl in aninteresting attitude of attention and with an obvious lack ofself-consciousness. The same monkey is represented again in figures 8and 9 of plate II, this time in the act of using hammer and saw. 

EXPLANATION OF PLATE II

FIGURE 3. --Orang utan, Julius, reaching for banana. 

FIGURE 4. --Julius walking across his cage. 

FIGURE 5. --_P. Rhesus_, Sobke. 

FIGURE 6. --Sobke stretching his jaws (yawn?) preparatory to a fight. 

FIGURE 7. --_P. Irus_, Skirrl. 

FIGURE 8. --Skirrl using hammer and nail. 

FIGURE 9. --Skirrl using a saw. 

All of the animals except the orang utan had been used more or less forexperiments on behavior by Doctor Hamilton, but this prior work in noway interfered with my own investigation. Doctor Hamilton hasaccumulated a large mass of the most valuable and interestingobservations on the behavior of monkeys, and he more thoroughlyunderstands them than any other observer of whom I have knowledge. Muchto my regret and embarrassment in connection with the present report, hehas thus far published only a small portion of his data (Hamilton, 1911, 1914). In his most recent paper on "A study of sexual tendencies inmonkeys and baboons, " he has given important information concerningseveral of the monkeys which I have observed. For the convenience ofreaders who may make use of both his reports and mine, I am designatingthe animals by the names previously given them by Hamilton. Theavailable and essential information concerning the individuals ispresented below. 

_List of animals in collection_

Skirrl. _Pithecus irus_. Adult male. 

Sobke. _P. Rhesus_. Young adult male. 

Gertie. _P. Irus-rhesus_. Female. Born November, 1910. 

Maud. _P. Rhesus_. Young adult female. 

Jimmy II. _P. Irus_. Adult male. 

Scotty. _P. Irus_ (?). Adult male. 

Tiny. _P. Irus-rhesus_. Female. Born August, 1913. 

Chatters. _P. Irus_. Adult eunuch. 

Daddy. _P. Irus_. Adult eunuch. 

Mutt. _P. Irus_. Young adult male. Born August, 1911. 

Julius. _Pongo pygmaeus_. Male. Age, 4 years to 5 years. 

When I arrived in Santa Barbara, Doctor Hamilton was about to remodel, or rather reconstruct, his animal cages and laboratory. This gave usopportunity to adapt both to the special needs of my experiments. Thelaboratory was finally located and built in a grove of live oaks. Fromthe front it is well shown by figure 10 of plate III, and from the rear, by figure 11. Its location was in every way satisfactory for my work, and in addition, the spot proved a delightful one in which to spendone's time. 

[Illustration: FIGURE 12. --Ground plan of Montecito laboratory andcages. Scale 1/120

L, laboratory; C, cages; A, experiment room in which multiple-choiceapparatus was installed; B, E, additional rooms for research; D, storeroom and shop; Z, large central cage communicating with the eightsmaller cages 1-8. ]

Figure 12 is a ground plan, drawn to scale, of the laboratory and theadjoining cages, showing the relations of the several rooms of thelaboratory among themselves and to the nine cages. Although theconstruction was throughout simple, everything was convenient and soplanned as to expedite my experimental work. The large room A, adjoiningthe cages, was used exclusively for an experimental study of ideationalbehavior by means of my recently devised multiple-choice method. Additional, and supplementary, experiments were conducted in the largecage Z. Room D served as a store-room and work-shop. 

The laboratory was forty feet long, twenty-two feet wide, and ten feetto the plate. Each small cage was six, by six, by twelve feet deep, while the large compartment into which each of the smaller cages openedwas twenty-four feet long, ten feet wide, and twelve feet deep. 

II

OBSERVATIONAL PROBLEMS AND METHODS

My chief observational task in Montecito was the study of ideationalbehavior, or of such adaptive behavior in monkeys and apes ascorresponds to the ideational behavior of man. It was my plan todetermine, so far as possible in the time at my disposal, the existenceor absence of ideas and the rôle which they play in the solution ofproblems by monkeys and apes. I had in mind the behavioristic form ofthe perennial questions: Do these animals think, do they reason, and ifso, what is the nature of these processes as indicated by thecharacteristics of their adaptive behavior?

My work, although obviously preliminary and incomplete, differs frommost of the previous studies of the complex behavior of the infrahumanprimates in that I relied chiefly upon a specially devised method andapplied it systematically over a period of several months. The work wasintensive and quantitative instead of more or less incidental, casual, and qualitative as has usually been the case. Naturally, during thecourse of my special study of ideational behavior observations were maderelative to various other aspects of the life of my subjects. Such, forexample, are my notes on the use of the hands, the instincts, theemotions, and the natural aptitudes of individuals. It is, indeed, impossible to observe any of the primates without noting mostinteresting and illuminating activities. And although the major portionof my time was spent in hard and monotonous work with my experimentalapparatus, I found time each day to get into intimate touch with thefree activities of my subjects and to observe their social relations andvaried expressions of individuality. As a result of my closeacquaintance with this band of primates, I feel more keenly than everbefore the necessity of taking into account, in connection with allexperimental analyses of behavior, the temperamental characteristics, experience, and affective peculiarities of individuals. 

The light which I have obtained on the general problem of ideation hascome, first, through a method which I have rather inaptly named themultiple-choice method, and second, and more incidentally, through avariety of supplementary methods which are described in Section IV ofthis report. These supplementary methods are simple tests of ideationrather than systematic modes of research. They differ from my chiefmethod, among other respects, in that they have been used by variousinvestigators during the past ten or fifteen years. It was not my aim torepeat precisely the observations made by others, but instead to verifysome of them, and more especially, to throw additional light on my mainproblem and to further the analysis of complex behavior. 

What has been referred to as the multiple-choice method was devised byme three years ago as a means of obtaining strictly comparable objectivedata concerning the problem-solving ability of various types andconditions of animals. The method was first tried with human subjects inthe Psychopathic Hospital, Boston, with a crude keyboard apparatuswhich, however, proved wholly satisfactory as a means of demonstratingits value. It has since been applied by means of mechanisms especiallyadapted to the structure and activities of the organisms, to the studyof the behavior of the crow, pig, rat, and ringdove (Yerkes, 1914;Coburn and Yerkes, 1915; Yerkes and Coburn, 1915). The method has alsobeen applied with most gratifying results to the study of thecharacteristics of ideational behavior in human defectives, --children, and adults, --and in subjects afflicted with various forms of mentaldisease. It is at present being tried out as a practical test inconnection with vocational guidance and various forms of institutionalexamination, such as psychopathic hospital and court examinations. 

As no adequate description of the method has yet been published to whichI can here refer, it will be necessary to present its salientcharacteristics along with a description of the special form ofapparatus which was found suitable for use with monkeys and apes. 

The method is so planned as to enable the observer to present to anytype or condition of organism which he wishes to study any one or all ofa series of problems ranging from the extremely simple to the complexand difficultly soluble. All of the problems, however, are completelysoluble by an organism of excellent ideational ability. For the humansubject, the solution of the easiest problem of all requires almost noeffort, whereas even moderately difficult problems may require manyrepetitions of effort and hours or days of application to the task. Ineach case, the solution of the problem depends upon the perception of acertain constant relation among a series of objects to which the subjectis required to attend and respond. Such relations are, for example, secondness from one end of the group, middleness, simple alternation ofends, or progressive movement by constant steps from one end of a groupto the other. 

It is possible to present such relational problems by means ofrelatively simple reaction-mechanisms. In their essential features, allof the several types of multiple-choice apparatus designed by the writerand used either by him or by his students and assistants are the same. They consist of a series of precisely similar reaction-devices, any oneor all of which may be used in connection with a given observation. These reaction-mechanisms are so chosen as to be suited to the structureand action-system of the animal to be studied. For the human being themechanism consists of a simple key and the total apparatus is a bank ofkeys, with such electrical connections as are necessary to enable theobserver to obtain satisfactory records of the subject's behavior. Letus suppose the bank of keys, as was actually the case in my first formof apparatus, to consist of twelve separate reaction-mechanisms; and letus suppose, further, the constant relation (problem) on the basis ofwhich the subject is required to react to be that of middleness. It isevident that in successive trials or experiments the keys must bepresented to the subject in odd groups, the possibilities being groupsof 3, 5, 7, 9, or 11. If for a particular observation the experimenterwishes to present the first three keys at the left end of the keyboard, he pushes back the remaining nine keys so that they cannot be operatedand requires the subject to select from the group of three keys the onewhich on being pressed causes a signal to appear. It is of course theclearly understood task of the subject to learn to select the correctkey in the group on first trial. This becomes possible only as thesubject observes the relation of the key which produces the desiredeffect to the other keys in the group. On the completion of a subject'sreaction to the group of three keys, a group of seven keys at theopposite end of the keyboard may, for example, be presented. Similarly, the subject is required to discover with the minimum number of trialsthe correct reaction-mechanism. Thus, time after time, the experimenterpresents a different group of keys so that the subject in no twosuccessive trials is making use of the same portion of the keyboard. Itis therefore impossible for him to react to spatial relations in theordinary sense and manner, and unless he can perceive and appropriatelyrespond to the particular relation which constitutes the only constantcharacteristic of the correct reaction-mechanism for a particularproblem, he cannot solve the problem, or at least cannot solve itideationally and on the basis of a small number of observations ortrials. 

For the various infrahuman animals whose ideational behavior has beenstudied by means of this method, it has been found eminentlysatisfactory to use as reaction-mechanisms a series of similar boxes, each with an entrance and an exit door. An incentive to the selection ofthe right box in a particular test is supplied by food, a small quantityof which is placed in a covered receptacle beyond the exit door of eachof the boxes. Each time an animal enters a wrong box, it is punished forits mistake by being confined in that box for a certain period, rangingfrom five seconds to as much as two minutes with various individuals ortypes of organism. This discourages random, hasty, or careless choices. When the right box is selected, the exit door is immediately raised, thus uncovering the food, which serves as a reward. After eating thefood thus provided, the animal, according to training, returns to thestarting point and eagerly awaits an opportunity to attempt once more tofind the reward which it has learned to expect. With this form of theapparatus, the boxes among which choice may be made are indicated by theraising (opening) of the front door. 

Since with various birds and mammals the box form of apparatus hadproved most satisfactory, I planned the primate apparatus along similarlines, aiming simply to adapt it to the somewhat different motorequipment and destructive tendencies of the monkeys. I shall now brieflydescribe this apparatus as it was constructed and used in the Montecitolaboratory. 

EXPLANATION OF PLATE IV

FIGURE 13. --Multiple-choice apparatus, showing observer's bench and writing stand. FIGURE 14. --Apparatus as seen from observer's bench. FIGURE 15. --Entrances to multiple-choice boxes as seen from the response-compartment. FIGURE 16. --Apparatus as seen from the rear, showing exit doors, food receptacles, and covers for same. 

The apparatus was built in room A (figure 12), this room having beenespecially planned for it with respect to lighting as well as dimensionsand approaches. It was unfortunately impossible to obtain photographsshowing the whole of the apparatus, but it is hoped that the fourpartial views of plate IV may aid the reader who is unfamiliar withpreviously described similar devices to grasp readily the chief pointsof construction. In this plate, figure 13 shows the front of thecomplete apparatus, with the alleyway and door by way of which theexperimenter could enter. The investigator's observation-bench andrecord-table also appear in this figure, together with weighted cordsused to operate the various doors and the vertically placed levers bymeans of which each pair of doors could be locked. Figure 14 is the viewpresented to the observer as he stood on the bench or observation standof figure 13 and looked over the entire apparatus. Three of the entrancedoors are shown at the right of this figure as raised, whereas theremainder of the nine entrance doors of the apparatus are closed. Figure15 is a view of the entrance doors from below the wire roof of theapparatus. Again, two of the doors are shown as raised, and threeadditional ones as closed. The rear of the apparatus appears in figure16, in which some of the exit doors are closed and others open. In thelatter case, the food receptacles appear, and on the lower part of theraised doors of the corresponding boxes may be seen metal covers for thefood receptacles projecting at right angles to the doors, while on thelower edge of each door is an iron staple used to receive a sliding barwhich could be operated from the observer's bench as a means of lockingthe doors after they had been closed. The space beyond the exit doorswas used as an alleyway for the return of the animals to the startingpoint. 

It will be necessary at various points in later descriptions to refer tothese several figures. But further description of them will be morereadily appreciated after a careful examination of the ground plan ofthe apparatus presented as figure 17 In accordance with the labelling ofthis figure, the experimenter enters the apparatus room through doorway16, passes thence through doorways 17 and 10 to the large cage Z, fromwhich he has direct access to the animals and can bring them into theapparatus. The multiple-choice mechanism proper, consisting of ninesimilar boxes (nine were used instead of twelve as a matter ofconvenience of construction, not because this smaller number isotherwise preferable) is labelled F. These boxes are numbered 1 to 9, beginning at the left. This numbering was adhered to in the recording ofresults throughout the investigation. The other important portions ofthe apparatus are the runway D, from which the subject at theexperimenter's pleasure could be admitted through doorway 12 to thelarge response-chamber E; the alleyways G, H, and I, by way of whichreturn to the starting point was possible; the observation bench C, withits approach step 13; and the observer's writing table A. 

In the construction of this large apparatus, it was necessary to makeprovision for the extremely destructive tendencies of monkeys andanthropoid apes, --hence the apparent cumbersomeness of certain portions. It was equally necessary to provide for the protection of the observerand the prevention of escape of the subjects by completely covering theapparatus and alleyways with a heavy wire netting. 

Each of the eighteen doors of the multiple-choice boxes, and in additiondoors 11, 12, and 15 of the runway D, were operated by the observer fromhis bench C by means of weighted window cords which were carried bypulleys appropriately placed above the apparatus. Each weight was sochosen as to be just sufficient to hold its door in position after theexperimenter had raised it. For the convenience of the experimenter inthe rapid operation of the twenty-one doors, the weights for the doorsof runway D were painted gray, those for the entrance doors, white, andthose for the exit doors, black. 

In each entrance door, as is shown in figure 15 of plate IV, a windowwas cut so that the experimenter might watch the animal after it hadentered a given box, and especially note when it left the box afterhaving received its reward. This window was covered with wire netting. No such windows were necessary in the exit doors, but to them wereattached heavy galvanized iron flanges which served to cover the foodreceptacles. One of these flanges is labelled o in figure 17. The foodreceptacles were provided by boring holes in a 2 by 4 inch timbersecurely nailed to the floor immediately outside of the exit doors. Intothese holes aluminum cups fitted snugly, and the iron flanges, when thedoors were closed, fitted so closely over the cups that it wasimpossible for the animals to obtain food from them. 

[Illustration: FIGURE 17. --Ground plan of multiple-choice apparatus inexperiment room A. Scale 1/60

A, record stand; C, bench for observer; B, step as approach to C; D, alleyway leading to E, response-compartment; F, one of the nine (1-9)similar multiple-choice boxes; G, H, alleyways leading from boxes tostarting point at D; I, alleyway used by experimenter as approach torear of apparatus; W, W, windows; P, alleyway; Z, large cage; 16, entrance to room A; 17, entrance to apparatus and thence via 10 tocages; 18, entrance to alleyway 1; 11, 15, entrances to D; 12, entranceto E; 13, entrance door of box 5; 14, exit door of box 5; o, cover forfood receptacle. ]

As originally constructed, no provision was made in the apparatus forlocking the entrance and exit doors of the several boxes when they wereclosed. But as two of the subjects after a time learned to open thedoors from either outside or inside the boxes, it became necessary tointroduce locking devices which could be operated by the experimenterfrom the observation bench. This was readily accomplished by cuttingholes in the floor, which permitted an iron staple, screwed to the loweredge of each door, to project through the floor. Through these staplesby means of a lever for each of the nine boxes, the observer was able toslide a wooden bar, placed beneath the floor of the room, thus lockingor unlocking either the entrance door, the exit door, or both, in thecase of any one of the nine boxes. 

Since figure 17 is drawn to scale, it will be needless to give more thana few of the dimensions of the apparatus. Each of the boxes was 42inches long, 18 inches wide, and 72 inches deep, inside measurements. The alleys D, I, and H were 24 inches, and G 30 inches wide, by 6 feetdeep. The doors of the several boxes were 18 inches wide, by 5 feethigh, while those in the alleyways were 24 inches wide by 6 feet high. The response-compartment E of figure 17 was 14 feet 4 inches, by 8 feet, by 6 feet in depth. In order that the apparatus might be used with adulthuman subjects conveniently, if such use should prove desirable, thedepth throughout was made 6 feet, and it was therefore possible for theexperimenter to walk about erect in it. 

The experimental procedure was briefly as follows: A small quantity offood having been placed in each of the food cups and covered by themetal flanges on the exit doors, the experimenter raised door 11 offigure 17 and then opened door 10 and the door of the cage in which thedesired subject was confined. After the latter, in search of food, hadentered the runway D, the experimenter lowered door 11 to keep it inthis runway, and immediately proceeded to set the reaction-mechanismsfor an experiment (trial). Let us suppose that the first setting to betried involved all of the nine boxes. Each of the entrance doors wouldtherefore be raised. Let us further suppose that the right door isdefined as the middle one of the group. With the apparatus properly set, the experimenter next raises door 12, thus admitting the animal to theresponse-compartment E. Any one of the nine boxes may now be entered byit. But if any except number 5, the middle member of the group, beentered, the entrance door is immediately lowered and both the exit andentrance doors locked in position so that the animal is forced to remainin the box for a stated period, say thirty seconds. At the expiration ofthis time the entrance door is raised and the animal allowed to retraceits steps and make another choice. When the middle box is chosen, theentrance door is lowered and the exit door immediately raised, thusuncovering the food, which the animal eats. As a rule, by my monkeys andape the reward was eaten in the alleyway G instead of in themultiple-choice box. As soon as the food has been eaten, the exit dooris lowered by the experimenter, and the animal returns by way of G and Hto runway D, where it awaits its next trial. 

As rewards, bananas and peanuts were found very satisfactory, andalthough occasionally other foods were supplied in small quantities, they were on the whole less constantly desired than the former. 

Four problems which had previously been presented to other organismswere in precisely the same form presented to the three primates. Theseproblems may be described, briefly, by definition of the right reactionmechanism, thus: problem 1, the first mechanism at the subject's left;problem 2, the second mechanism at the subject's right (that is, fromthe end of the series at the subject's right); problem 3, alternately, the first mechanism at the subject's left and the first at its right;problem 4, the middle mechanism of the group. 

It was my intention to present these four problems, in order, to each ofthe three animals, proceeding with them as rapidly as they were solved. But as it happened, only one of the three subjects got as far as thefourth problem. When observations had to be discontinued, Sobke was wellalong with the last, or fourth problem; Skirrl was at work at the thirdproblem; and Julius had failed to solve the second problem. 

For each of the problems, a series of ten different settings of thedoors was determined upon in advance. These settings differ from thoseemployed in a similar investigation with the pig only in that thenumbering of the doors is reversed. In the present apparatus, the boxesas viewed from the front (entrance) are numbered from the left to theright end, whereas those of the pig apparatus were numbered from theright end to the left end. 

Below are presented for each of the several problems (1) the numbers ofthe settings presented in series; (2) the numbers of the doors open; (3)the number of doors open in each setting and for the series of tensettings; and (4) the number of the right door. 

PROBLEM 1. First mechanism at left of group

 Doors No. Of No. OfSettings open doors open right door 1.................. 1. 2. 3...................... 3.................. 1 2.................. 8. 9........................ 2.................. 8 3.................. 3. 4. 5. 6. 7.................. 5.................. 3 4.................. 7. 8. 9...................... 3.................. 7 5.................. 2. 3. 4. 5. 6.................. 5.................. 2 6.................. 6. 7. 8...................... 3.................. 6 7.................. 5. 6. 7...................... 3.................. 5 8.................. 4. 5. 6. 7. 8.................. 5.................. 4 9.................. 7. 8. 9...................... 3.................. 710.................. 1. 2. 3...................... 3.................. 1 -- Total 35

PROBLEM 2. Second mechanism from the right end of group

 Doors No. Of No. OfSettings open doors open right door 1.................. 7. 8. 9...................... 3.................. 8 2.................. 1. 2. 3. 4.................... 4.................. 3 3.................. 2. 3. 4. 5. 6. 7................ 6.................. 6 4.................. 1. 2. 3. 4. 5. 6................ 6.................. 5 5.................. 4. 5. 6. 7. 8.................. 5.................. 7 6.................. 1. 2. 3...................... 3.................. 2 7.................. 2. 3. 4. 5.................... 4.................. 4 8.................. 1. 2. 3. 4. 5. 6. 7. 8. 9.......... 9.................. 8 9.................. 1. 2. 3. 4.................... 4.................. 310.................. 3. 4. 5. 6. 7. 8................ 6.................. 7 -- Total 50

PROBLEM 3. Alternately the first mechanism at the left and the first at the right end of the group

 Doors No. Of No. OfSettings open doors open right door 1.................. 5. 6. 7...................... 3.................. 5 2.................. 5. 6. 7...................... 3.................. 7 3.................. 1. 2. 3. 4. 5. 6................ 6.................. 1 4.................. 1. 2. 3. 4. 5. 6................ 6.................. 6 5.................. 4. 5. 6. 7. 8.................. 5.................. 4 6.................. 4. 5. 6. 7. 8.................. 5.................. 8 7.................. 2. 3. 4. 5.................... 4.................. 2 8.................. 2. 3. 4. 5.................... 4.................. 5 9.................. 3. 4. 5. 6. 7. 8. 9.............. 7.................. 310.................. 3. 4. 5. 6. 7. 8. 9.............. 7.................. 9 -- Total 50

PROBLEM 4. Middle mechanism of the group

 Doors No. Of No. OfSettings open doors open right door 1.................. 2. 3. 4...................... 3.................. 3 2.................. 5. 6. 7. 8. 9.................. 5.................. 7 3.................. 1. 2. 3. 4. 5. 6. 7.............. 7.................. 4 4.................. 7. 8. 9...................... 3.................. 8 5.................. 4. 5. 6. 7. 8.................. 5.................. 6 6.................. 1. 2. 3. 4. 5. 6. 7. 8. 9.......... 9.................. 5 7.................. 1. 2. 3...................... 3.................. 2 8.................. 2. 3. 4. 5. 6.................. 5.................. 4 9.................. 3. 4. 5. 6. 7. 8. 9.............. 7.................. 610.................. 6. 7. 8...................... 3.................. 7 -- Total 50

It was found desirable after a problem had been solved to present a newand radically different series of settings in order to determine to whatextent the subject had learned to choose the correct door by memorizingeach particular setting. These supplementary observations may be knownas control experiments, and the settings as supplementary settings. Incase of these, as for the original settings, the essential facts arepresented in tabular arrangement. 

Settings for Control Experiments

PROBLEM 1. First at left end

 Doors No. Of No. OfSettings open doors open right door 1.................. 2. 3. 4...................... 3.................. 2 2.................. 6. 7. 8. 9.................... 4.................. 6 3.................. 3. 4. 5...................... 3.................. 3 4.................. 4. 5. 6. 7. 8. 9................ 6.................. 4 5.................. 6. 7. 8. 9.................... 4.................. 6 6.................. 1. 2. 3. 4. 5.................. 5.................. 1 7.................. 2. 3. 4. 5. 6. 7. 8.............. 7.................. 2 8.................. 3. 4. 5. 6. 7. 8................ 6.................. 3 9.................. 5. 6. 7...................... 3.................. 510.................. 1. 2. 3. 4. 5. 6. 7. 8. 9.......... 9.................. 1

PROBLEM 2. Second from right end

 Doors No. Of No. OfSettings open doors open right door 1.................. 5. 6. 7. 8.................... 4.................. 7 2.................. 2. 3. 4. 5. 6.................. 5.................. 5 3.................. 1. 2. 3. 4. 5. 6. 7. 8. 9.......... 9.................. 8 4.................. 5. 6. 7...................... 3.................. 6 5.................. 1. 2. 3. 4.................... 4.................. 3 6.................. 4. 5. 6...................... 3.................. 5 7.................. 2. 3. 4. 5.................... 4.................. 4 8.................. 1. 2. 3...................... 3.................. 2 9.................. 1. 2. 3. 4. 5. 6. 7.............. 7.................. 610.................. 2. 3. 4. 5. 6. 7. 8. 9............ 8.................. 8

PROBLEM 3. Alternate left and right ends

 Doors No. Of No. OfSettings open doors open right door 1.................. 5. 6........................ 2.................. 5 2.................. 5. 6........................ 2.................. 6 3.................. 4. 5. 6. 7. 8. 9................ 6.................. 4 4.................. 4. 5. 6. 7. 8. 9................ 6.................. 9 5.................. 1. 2. 3. 4. 5.................. 5.................. 1 6.................. 1. 2. 3. 4. 5.................. 5.................. 5 7.................. 2. 3. 4. 5. 6. 7................ 6.................. 2 8.................. 2. 3. 4. 5. 6. 7................ 6.................. 7 9.................. 3. 4. 5. 6. 7. 8................ 6.................. 310.................. 3. 4. 5. 6. 7. 8................ 6.................. 8

PROBLEM 4. Middle

 Doors No. Of No. OfSettings open doors open right door 1.................. 4. 5. 6. 7. 8.................. 5.................. 6 2.................. 1. 2. 3...................... 3.................. 2 3.................. 1. 2. 3. 4. 5. 6. 7. 8. 9.......... 9.................. 5 4.................. 2. 3. 4. 5. 6.................. 5.................. 4 5.................. 6. 7. 8...................... 3.................. 7 6.................. 3. 4. 5. 6. 7. 8. 9.............. 7.................. 6 7.................. 7. 8. 9...................... 3.................. 8 8.................. 1. 2. 3. 4. 5. 6. 7.............. 7.................. 4 9.................. 2. 3. 4...................... 3.................. 310.................. 3. 4. 5. 6. 7.................. 5.................. 5

It was my aim so far as possible to present to a given subject each daythe ten settings under a given problem in order, without interruption. If for any reason the series of observations had to be interrupted, itwas resumed at the same point subsequently. Occasionally it was founddesirable or necessary to present only five of the series of tensettings in succession and then to interrupt observations for aninterval of a few minutes or even several hours. But as a rule it waspossible to present the series of ten settings. All things beingconsidered, it proved more satisfactory to give only ten trials a day toeach subject. Frequently twenty and rarely thirty trials were given onthe same day. In such cases the series of settings was simply repeated. The only pause between trials was that necessary for resetting theentrance doors and replenishing the food which served as a reward forsuccess. 

III

RESULTS OF MULTIPLE-CHOICE EXPERIMENTS

1. Skirrl, _Pithecus irus_

_Problem 1. First at the Left End_

Systematic work with the multiple-choice apparatus and method describedin the previous section was undertaken early in April with Skirrl, Sobke, and Julius. The results for each of them are now to be presentedwith such measure of detail as their importance seems to justify. 

Skirrl had previously been used by Doctor Hamilton in an experimentalstudy of reactive tendencies. He proved so remarkably inefficient in thework that Doctor Hamilton was led to characterize him as feeble-minded, and to recommend him to me for further study because of his mentalpeculiarities. With me he was from the first frank, aggressive, andinclined to be savage. It was soon possible for me to go into the largecage, Z, with him and allow him to take food from my hand. He waswithout fear of the experimental apparatus and it proved relatively easyto accustom him to the routine of the experiment. Throughout the work hewas rather slow, inattentive, and erratic. 

Beginning on April 7, I sought to acquaint him with the multiple-choiceapparatus by allowing him to make trips through the several boxes, withthe reward of food each time. Thus, for example, with the entrance andexit doors of box 7 raised, the monkey was allowed to pass into thereaction-compartment E and thence through box 7 to the food cup. As soonas he had finished eating, he was called back to D by the experimenterand, after a few seconds, allowed, similarly, to make a trip by way ofone of the other boxes. By reason of this preliminary training he sooncame to seek eagerly for the reward of food. 

On April 10 the apparatus was painted white in order to increase thelightness and thus render it easier for the experimenter to observe theanimal's movements, and when on April 12 Skirrl was again introduced toit for further preliminary training, he utterly refused to enter theboxes, giving every indication of extreme fear of the white floors andeven of the sides of the boxes. Finally, the attempts to induce him toenter the boxes had to be given up, and he was returned to his cageunfed. The following day I was equally unsuccessful in either driving ortempting him with food into the apparatus. But on April 14 he was sohungry that he was finally lured in by the use of food. He cautiouslyapproached the boxes and attempted to climb through on the sides insteadof walking on the floor. It was perfectly evident that he had aninstinctive or an acquired fear of the white surfaces. As the matter wasof prime importance for the success of my work, I inquired of DoctorHamilton, and of the men in charge of the cages, for any incident whichmight account for this peculiar behavior, and I learned that some threemonths earlier, while the animal cages were being whitewashed, Skirrlhad jumped at one of the laborers who was applying a brush to theframework of one of the cages and had shaken some lime into his eyes. Hewas greatly frightened and enraged. Evidently he experienced extremediscomfort, if not acute pain, and there resulted an association withwhiteness which was quite sufficient to cause him to avoid the freshlypainted apparatus. 

Having obtained an adequate explanation of this monkey's peculiarbehavior, I proceeded with my efforts to induce him to work smoothly andrapidly, and on April 15, by covering the floor with sawdust, I sodiminished the influence of the whiteness as to render the preliminarytraining fairly satisfactory. At the end of two more days everything wasgoing so well that it seemed desirable to begin the regular experiment. 

On the morning of April 19, Skirrl was introduced to the apparatus andgiven his first series of ten trials on problem 1. This problem demandedthe selection of the first door at the left in any group of open doors. The procedure was as previously described in that the experimenterraised the entrance doors of a certain group of boxes, admitted theanimal to the reaction-chamber, punished incorrect choices by confiningthe animal for thirty seconds, and rewarded correct choices by raisingthe exit door and thus permitting escape and the obtaining of food. Thetrials were given in rapid succession, and the total time required forthis first series of ten trials was thirty-five minutes. Skirrl workedfaithfully throughout this interval and exhibited no markeddiscouragement. When confined in a box he showed uneasiness anddissatisfaction by moving about constantly, shaking the doors, andtrying to raise them in order to escape. 

For the series of settings used in connection with problem 1, the readeris referred to page 18. In the first setting, the doors numbered 1, 2, and 3, were opened. As it happened, the animal when admitted to thereaction-chamber immediately chose box l. Having received the reward offood, he was called back to D, and doors 8 and 9 having been raised inpreparation for the next trial, he was again admitted to thereaction-chamber. This time he quickly chose box 9 and was confinedtherein for thirty seconds. On being released, he chose after aninterval of four minutes, box 8, thus completing the trial. 

As it is highly important, not only in connection with the presentdescription of behavior, but also for subsequent comparison of thereactions of different types of organism in this experiment, to presentthe detailed records for each trial, tables have been constructed whichoffer in brief space the essential data for every trial in connectionwith a given problem. 

Table 1 contains the results for Skirrl in problem 1. It is constructedas follows: the date of a series of trials appears in the first verticalcolumn; the numbers (and number) of the trials for the series or dateappear in column 2; the following ten columns present respectively theresults of the trials for each of the ten settings. Each number, inthese results, designates a box entered. At the extreme right of thetable are three columns which indicate, first, the number of trials inwhich the right box was chosen first, column headed R; and second, thenumber of trials in which at least one incorrect choice occurred, columnheaded W. In the last column, the daily ratio of these first choicesappears. 

Taking the first line of table 1 below the explanatory headings, we noteon April 19 ten trials, numbered 1 to 10, were given to Skirrl. In trial1, with setting 1, he chose correctly the first time, and the record istherefore simply 1. In trial 2, setting 2, he incorrectly chose box 9, the first time. At his next opportunity, he chose box 8, which was theright one. The record therefore reads 9. 8. In trial 3, setting 3, hechose incorrectly twice before finally selecting the right box. Therecord reads 6. 7. 3, and so on throughout the ten trials which constitutea series. The summary for this series indicates three right and sevenwrong first choices, that is, three cases in which the right box wasentered first. The ratio of right to wrong first choices is therefore 1to 2. 33. Since the total number of doors open in the ten settings isthirty-five, and since in each of the ten settings one door isdescribable as the right door, the probable ratio, apart from theeffects of training, of right to wrong first choices is 1 to 2. 50. It isevident, therefore, that Skirrl in his first series of trials closelyapproximated expectation in the number of mistakes. 

TABLE 1

Results for Skirrl, _P. Irus_, in Problem 1

========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | RatioDate | of | | | | | | | | | | | R | W | of | trials | 1. 2. 3 | 8. 9 | 3. 4. 5. 6. 7 | 7. 8. 9 | 2. 3. 4. 5. 6 | 6. 7. 8 | 5. 6. 7 | 4. 5. 6. 7. 8 | 7. 8. 9 | 1. 2. 3 | | | R to W--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- April | | | | | | | | | | | | | | 19 | 1- 10 | 1 | 9. 8 | 6. 7. 3 | 9. 7 | 6. 2 | 7. 8. 6 | {6. 7. 7. 7 | 4 | 7 | 2. 3. 3. 1 | 3 | 7 | 1:2. 33 | | | | | | | | {6. 5 | | | | | | | | | | | | | | | | | | | | 20 | 11- 20 | 3. 2. 1 | 9. 8 | 5. 3 | 7 | 4. 2 | 8. 8. 6 | 5 | 8. 4 | 7 | 3. 1 | 3 | 7 | 1:2. 33 21 | 21- 30 | 3. 1 | 8 | 3 | 8. 7 | 6. 2 | 6 | 5 | 6. 4 | 9. 7 | 1 | 5 | 5 | 1:1. 00 22 | 31- 40 | 1 | 9. 8 | 3 | 7 | 6. 2 | 6 | 6. 7. 5 | 5. 8. 4 | 9. 8. 9. 8. 7 | 2. 1 | 4 | 6 | 1:1. 50 23 | 41- 50 | 2. 3. 1 | 8 | 5. 7. 3 | 7 | 4. 2 | 6 | 5 | 7. 8. 4 | 7 | 3. 1 | 5 | 5 | 1:1. 00 24 | 51- 60 | 1 | 8 | 4. 5. 7. 3 | 9. 7 | 5. 6. 2 | 6 | 6. 7. 5 | 6. 4 | 8. 9. 7 | 1 | 4 | 6 | 1:1. 50 26 | 61- 70 | 1 | 8 | 6. 7. 4. 7. 3 | 7 | 4. 5. 6. 2 | 6 | 5 | 8. 4 | 7 | 3. 2. 3. 1 | 6 | 4 | 1: . 67 27 | 71- 80 | 3. 1 | 8 | 3 | 9. 7 | 4. 6. 2 | 7. 6 | 6. 5 | 5. 8. 4 | 7 | 1 | 4 | 6 | 1:1. 50 28 | 81- 90 | 2. 3. 1 | 8 | 3 | 7 | 4. 5. 6. 2 | 6 | 5 | 5. 8. 4 | 7 | 1 | 7 | 3 | 1: . 43 29 | 91- 100 | 1 | 8 | 3 | 9. 7 | 6. 2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: . 25 30 | 101- 110 | 1 | 8 | 4. 3 | 7 | 5. 6. 2 | 6 | 5 | 4 | 7 | 2. 3. 1 | 7 | 3 | 1: . 43 May | | | | | | | | | | | | | | 1 | 111- 120 | 2. 3. 2. 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: . 11 3 | 121- 130 | 1 | 8 | 5. 6. 3 | 7 | 4. 5. 2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: . 254 and 5 | 131- 140 | 3. 2. 1 | 8[1] | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: . 11 5 | 141- 150 | 1 | 8 | 4. 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: . 11--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- | | | | | | | | 2. 3. 4. 5 | | | 1. 2. 3. 4. 5 | | | | | 2. 3. 4 | 6. 7. 8. 9 | 3. 4. 5 | 4. 5. 6. 7. 8. 9 | 6. 7. 8. 9 | 1. 2. 3. 4. 5 | 6. 7. 8 | 3. 4. 5. 6. 7. 8 | 5. 6. 7 | 6. 7. 8. 9 | | | | +---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- 6 | 1- 10 | 2 | 6 | 3 | 4 | 6 | 3. 2. 1 | 6. 2 | 5. 6. 7. 8. 3 | 5 | 6. 1 | 6 | 4 | 1: . 67========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+========

[Footnote 1: End of series on May 4. ]

By reading downward in any particular column of results, one obtains adescription of the changes in the animal's reaction to a particularsetting of the doors. Thus, for instance, in the case of setting 1, which was presented to the animal in trials numbered 1, 11, 21, and soon to 141, it is clear from the records that no definite improvementoccurred. But oddly enough, in the case of setting 10, which presentedthe same group of open doors, almost all of the reactions are right inthe lower half of the column. For setting 2, it is evident that mistakessoon disappeared. 

Comparison of the data of table 1 indicates that the number of correctfirst choices is inversely proportional to the number of doors in use, while the number of choices made in a given trial is directlyproportional to the number of doors in use. 

During the first week of work on this problem, Skirrl improved markedly. His performance was somewhat irregular and unpredictable, but on thewhole the experiment seemed fairly satisfactory. Cold, cloudy, or rainydays tended to diminish steadiness and to increase the number ofmistakes. Similarly, absence of hunger was unfavorable to continuouseffort to find the right box. 

The period of confinement, as punishment for wrong choices, wasincreased from thirty seconds to sixty seconds on April 26. But there isno satisfactory evidence that this favored the solution of the problem. Work on May 4 was interrupted by a severe storm, the noise of which sodistracted the monkey that he ceased to work. Consequently, observationswere interrupted on the completion of trial 132, and on May 5, theseries was begun with setting 3. On this date, eighteen trials weregiven in succession, and in only one of them did a mistake occur. Sincethe ten trials numbered 133 to 142 were correct, Skirrl was consideredto have solved problem 1, and systematic training was discontinued. 

On the following day, as a measure of the extent to which the animal hadlearned to select the first door at the left no matter what its positionor the number of doors in the group presented, a control series wasgiven in which the settings differed from the regular series ofsettings. These supplementary settings are presented at the bottom oftable 1 together with the records of reaction in ten trials. 

Since in only six of these ten control settings was the first choicecorrect, it is scarcely fair to insist that the animal was reacting onthe basis of an ideational solution of the problem. Rather, it wouldseem that he had learned to react to particular settings. A carefulstudy of all of the data of response, together with notes on the variedbehavior of the animal during the experiments, justifies the statementthat Skirrl's solution of problem 1 was incomplete and unreliable. Itwas highly dependent upon the particular situation, or even theparticular door at the left end of the group, and slightly if at alldependent upon anything comparable to the human idea of first at theleft of the group. 

This particular series of observations has been described and discussedin some detail in order to make the chief points of method clear. Itwill be needless, hereafter, to refer explicitly to many of thecharacteristics of reaction or to the important points in theconstruction of tables which have been mentioned. 

A graphic representation of Skirrl's learning process in problem 1 ispresented in figure 18. The irregularities are most striking, and fairlyindicate the erraticness of the animal. The curve is based upon the datain next to the last column of table 1, that is, the column presentingthe errors or wrong first choices in each series of trials. 

Unquestionably, the form of such a curve of learning should beconsidered in connection with the method or methods of selecting theright box employed by the animal during the course of experimentation. It appears from an analysis of the behavior of Skirrl in problem 1 thatthere developed a single definite and persistent method, namely, that ofgoing to one box in the group, and in case it happened to be a wrongone, of choosing, on emergence from it, the next toward the right end ofthe group, and so on down the line. Having reached the extreme rightend, the tendency was to follow the side of the reaction-chamber aroundto the opposite end and to enter the first box at the left end of thegroup, which was, of course, the right one. This method appears, withcertain slight variations, in approximately ninety per cent of thetrials which involved incorrect choices. Thus, in the case of trials 121to 130, of which eight exhibit right first choices, the remaining twoexhibit the method described above except that the final member at theright end of the group was in each case omitted. 

[Illustration: FIGURE 18. --Error curves of learning for the solution ofproblem 1 (first box at left end). ]

On the whole, Skirrl's behavior in connection with this problem appearsto indicate a low order of intelligence. He persisted in such stupidacts as that of turning, after emergence from the right box, toward theright and passing into the blind alley I, instead of toward the left, through G and H, to D. In contrast with the other animals, he spent muchtime before the closed doors of the boxes, instead of going directly tothe open doors, some one of which marked the box in which the reward offood could be obtained. It is, moreover, obvious that his responses, asthey appear in table 1, are extremely different from those of a humanbeing who is capable of bringing the idea of first at the left end tobear upon the problem in question. 

_Problem 2. Second from the Right End_

Following the series of control trials of problem 1 given to Skirrl onMay 6, a period of four days was allowed during which the animal wasmerely fed in the boxes each day. This was done in order that he shouldpartially lose the effects of his previous training to choose the firstbox at the left before being presented with the second problem, thesecond box from the right. 

On May 11 regular experimentation was begun with problem 2. Naturallythe situation presented unusual difficulties to the monkey because ofhis previously acquired habit, and on the first day it was possible togive only five trials, in all except the first of which Skirrl had to beaided by the experimenter to find the right box. He persistently, asappears in the first line of records of table 2, entered the first boxat the left. The series was continued on May 13, but with veryunsatisfactory results, since he apparently had been greatly discouragedby the unusual difficulties previously met. Only four trials could begiven, and in these the showing made was very poor. It is noteworthy, however, that in trials 6, 7, and 8, May 13, there was no markedtendency to choose the first box at the left. Thus quickly had the forceof the previous habit been broken. 

For problem 2, the total number of open doors in the ten settings isfifty, as appears from the data on page 18, and as ten of these fiftyopen doors may be defined as right ones, the expected ratio of right towrong first choices in the absence of previous training is 1 to 4. Theactual ratio for the first series given in problem 2 is 1 to 8, while inthe second series it is 0 to 10. 

On the morning of May 13, work was interrupted in the ninth trial bywhat seemed at the moment a peculiarly unfortunate accident, but in thelight of later developments, an incident most fruitful of valuableresults. 

Skirrl, in trial 9, directly entered box 1. Since this was not the rightbox, he was punished by being confined in it for ten seconds. While inthe box he howled and when the entrance door was raised for him toretrace his steps, he came out with a rush, showing extreme excitementand either rage or fear, I could not be sure which. At intervals heuttered loud cries, which I am now able to identify as cries of alarm. Repeatedly he went to the open door of box 1 and peered in, or peereddown through the hole in the floor which received the staple on thedoor. He refused to enter any one of the open boxes and continued, atintervals of every half minute or so, his cries. For thirty minutes Iwaited, hoping to be able to induce him to complete the series oftrials, but in vain. Although it was obvious that he was eager to escapefrom the apparatus, he would not enter any of the boxes even when theexit doors were raised. Instead, he gnawed at the door (12 in fig. 17)to the alleyway D and attempted to force his way through, instead oftaking the easy and clear route to the alleys, through one of the boxes. His behavior was most surprising and puzzling. Finally, I gave up theattempt to complete the series and returned him to his cage by way ofthe entrance door to the response-compartment E. 

I then entered the apparatus to seek some explanation of the animal'sbehavior, and my search was rewarded by the finding of two sharp pointednails which protruded for an inch or more in the middle of the floor ofbox 1. My assistant, who had been charged with the task of installingthe locks for the several doors, had used nails instead of screws forattaching staples underneath the floor and had neglected to clinch thenails. Skirrl, in the dim light of the box, doubtless stepped upon oneof the nails and inflicted a painful, although not serious, injury uponhimself. It was impossible for him to see clearly the source of hisinjury. He was greatly frightened and expressed the emotion mostvigorously. His behavior strongly suggested a superstitious dread ofsome unseen danger. It may be that the instinctive fear of snakes, sostrong in monkeys, was partly responsible for his response. 

The first result of this accident was that more than two weeks werelost, for it was impossible, during the next few days, to induce theanimal to enter any of the multiple-choice boxes voluntarily. From May14 to May 24, I labored daily to overcome his newly acquired fear. Theusual procedure was to coax him through one box after another bystanding at the exit door with some tempting morsel of food. Afterseveral days of this treatment, he again trusted himself to the boxes, although very circumspectly and only when both entrance and exit doorswere raised. Not until May 24 was it possible to resume regularexperimentation, and on that day it was found necessary to indicate theright box by raising the exit door slightly and then immediatelylowering it. Trials in which this form of aid was given are indicated intable 2 by a star following the last choice. 

Gradually, Skirrl regained his confidence in the apparatus and began towork more naturally. For a long time he would not stand punishment, andit was necessary for the experimenter to be very careful in locking thedoors, since the sound of the bar sliding beneath the floor oftenfrightened and caused him to quit work. Day after day the tendency topeer through the holes in the floor at the entrance to the boxesrendered it clear that the animal feared some danger from beneath thefloor. This behavior was so persistent that much time was wasted in theexperiments. 

On the last day of May, punishment by confinement for ten seconds inwrong boxes was introduced, but since this tended to discourage themonkey, there was substituted for it on June 1 the punishment of forcinghim to work his way out of each wrong box by raising the entrance doorwhich had been closed behind him. This he could fairly readily do, andhis stay in a box rarely measured more than ten seconds. 

As a variation in the mode of procedure, confinement for thirty secondswas tried on June 5, but it worked unsatisfactorily and had to beabandoned. During this series, the animal was startled by the sound fromone of the sliding bars under the floor, and in the sixth trial herefused to work. 

As improvement was very slow, varied modes of rewarding and punishingthe animal were tried in the hope of discovering a means of facilitatingthe work. Among the former are the use of banana, grapes, peanuts, andother eagerly sought foods in varying quantities, and in the latter areincluded periods of confinement ranging from ten seconds to sixtyseconds. In the end, confinement of about thirty seconds, combined witha small quantity of food which was much to the monkey's taste, gave mostfavorable results. 

All this time Skirrl's attention to the task in hand was seldom good. Hewas easily diverted and even when extremely hungry, often stopped workin the middle of an early trial, yawned repeatedly and finally sat downto wait for release from the apparatus. 

The results obtained during the long continued trials with this animalin problem 2 are presented in table 2, which differs from the previouslydescribed table, first, in that several of the trials are followed by anasterisk to indicate that aid was given by the experimenter, and second, in that two additional columns, headed, respectively, R and W, arepresented. These give the right and wrong first choices for each day, whereas the two columns preceding them give the same data for eachseries of ten trials. Similarly, the ratio of right to wrong choices ispresented for each day in table 2, instead of for each series of tentrials as in table 1. 

From the results of table 2, several peculiarly interesting factsappear. In the first place the influence of the habit of choosing thefirst box at the left disappears with surprising suddenness, and in thesecond place, there are remarkable contrasts in the results fordifferent settings as they appear in their respective vertical columns. Thus, in the case of setting 1, after the first trial mistakes becamerelatively infrequent, whereas in setting 6, which involved the samenumber of doors, mistakes continued to be the rule until nearly athousand trials had been given. The most likely explanation of thisdifference is that for some reason the animal avoided box 9. 

The _reactive tendencies_, or better, the _methods of reaction_ whichmanifested themselves during this long series of observations may bedescribed as follows: (a) choice of the first box at the left; (b)random choice with tendency to choose first, a box near the middle ofthe group; (c) choice of first box at the right followed by the one nextto it on the left; (d) direct choice of the right box. 

TABLE 2

Results for Skirrl, _P. Irus_, in Problem 2

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | | | | | | 1. 2. 3. 4. 5 | | | R | W | R | W | of | trials | 7. 8. 9 | 1. 2. 3. 4 | 2. 3. 4. 5. 6. 7 | 1. 2. 3. 4. 5. 6 | 4. 5. 6. 7. 8 | 1. 2. 3 | 2. 3. 4. 5 | 6. 7. 8. 9 | 1. 2. 3. 4 | 3. 4. 5. 6. 7. 8 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- May | | | | | | | | | | | | | | | | 11&13 | 1- 9 | 7. 7. 9. 7. 8 | {1. 2. 2. 1. 4. 1 | {2. 3. 2. 3. 2. 5 | {4. 6. 1. 4. 1. 1 | 4. 4. 7 | 3. 1. 2 | 4 | 4. 1. 8 | 1 | | 1 | 8 | 1 | 8 | 1: 8. 00 | | | {2. 1. 2. 1. 3 | {2. 3. 2. 5. 6 | {2. 6. 1. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | 24 | 11- 20 | 8*[1] | 2. 4. 3* | 4. 5. 6* | 2. 2. 5* | 5. 6. 6. 7* | 3. 1. 2 | {5. 2. 3. 5. 3. 2 | 4. 6. 8* | 4. 4. 3* | 5. 5. 6. 7* | 0 |10 | 0 |10 | 0:10. 00 | | | | | | | | {3. 5. 2. 4* | | | | | | | | | | | | | | | | | | | | | | | | 25 | 21- 30 | 8* | 4. 4. 3* | 5. 6 | {6. 6. 2. 3. 4 | 6. 7 | 2 | 4 | 5. 6. 3. 8 | 4. 4. 3 | 6. 4. 6. 8. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | {6. 6. 5* | | | | | | | | | | | | | | | | | | | | | | | | | | | 26 | 31- 40 | 8 | 4. 3 | 6 | 4. 5 | 6. 7 | 3. 2 | 5. 4 | 5. 8 | 4. 3 | 5. 3. 8. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | | | | | | | | | | | | 27 | 41- 50 | 8 | 4. 4. 3 | 6 | 5 | 6. 8. 6. 8. 7 | 3. 3. 3. 2 | 5. 4 | {6. 5. 4. 3 | 4. 3 | 5. 4. 8. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 | | | | | | | | | {2. 1. 5. 8 | | | | | | | | | | | | | | | | | | | | | | | 28 | 51- 60 | 8 | 4. 4. 3 | 7. 6 | 5 | 5. 6. 7 | 3. 3. 3. 2 | 4 | {5. 4. 3 | 4. 3 | {5. 4. 3. 3. 4. 5 | 3 | 7 | 3 | 7 | 1: 2. 33 | | | | | | | | | {3. 6. 8 | | {6. 4. 3. 5. 7 | | | | | | | | | | | | | | | | | | | | | 29 | 61- 70 | 8 | 4. 3 | 6 | 6. 6. 5 | 7 | 3. 3. 3. 2 | 5. 4 | 7. 6. 4. 7. 6. 8 | 4. 3 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | | | | | | | | 31 | 71- 80 | 8 | 4. 4. 4. 3 | 6 | 6. 5 | 6. 8. 7 | 3. 2 | 5. 4 | {6. 7. 6. 4. 3 | 4. 3 | 6. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 June | | | | | | | | | {2. 6. 3. 7. 8 | | | | | | | | | | | | | {6. 8. 6. 5. 4 | | | | | | | | | | 1 | 81- 90 | 8 | 4. 3 | 6 | 5 | {6. 5. 6. 5. 8 | 3. 1. 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 5 | 5 | | | | | | | | | {5. 4. 6. 4. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | " | 91- 100 | 9. 7. 8 | 4. 2. 4. 3 | 7. 5. 6 | 5 | 6. 8. 7 | 3. 3. 1. 2 | 5. 3. 4 | 8 | 4. 3 | 6. 8. 7 | 2 | 8 | 7 |13 | 1: 1. 86 2 | 101- 110 | 8 | 4. 3 | 6 | 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 6. 8. 6. 5. 7 | 4 | 6 | | | | | | | | | | | | | | | | | | | " | 111- 120 | 8 | 4. 3 | 7. 3. 5. 7. 6 | {6. 2. 3. 6. 4 | 7 | 3. 2 | {5. 2. 3. 5. 3. 2 | 9. 6. 4. 7. 8 | {4. 1. 2 | 6. 8. 7 | 2 | 8 | 6 |14 | 1: 2. 33 | | | | | {3. 6. 2. 5 | | | {3. 5. 2. 3. 4 | | {4. 2. 3 | | | | | | | | | | | | | | | | | {6. 8. 6. 3 | | | | | 3 | 121- 130 | 8 | 4. 4. 3 | 6 | 5 | 6. 7 | 3. 2 | {5. 3. 2. 3 | 8 | 4. 2. 3 | {5. 4. 5. 8. 8 | 4 | 6 | | | | | | | | | | | {5. 2. 5. 4 | | | {6. 3. 8. 7 | | | | | | | | | | | | | | | | | | | | | " | 131- 140 | 8 | 4. 3 | 5. 7. 3. 2. 6 | 4. 5 | 5. 7 | 1. 3. 2 | 5. 3. 4 | 6. 7. 8 | 4. 2. 1. 3 | 7 | 2 | 8 | 6 |14 | 1: 2. 33 | | | | | | | | | | | | | | | | 4 | 141- 150 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 2 | {5. 3. 2. 3 | 6. 8 | 4. 1. 3 | 5. 6. 7 | 3 | 7 | | | | | | | | | | | {5. 5. 4 | | | | | | | | | | | | | | | | | | | | | | | | " | 151- 160 | 8 | 4. 3 | 6 | 5 | 6. 7 | 2 | 4 | 5. 6. 7. 8 | 4. 3 | 5. 6. 8. 7 | 5 | 5 | 8 |12 | 1: 1. 50 5 | 161- 170 | 8 | 4. 3 | 7. 6 | 6. 5 | 6. 8. 7 | 3. 2 | 5. 3. 2. 3. 5. 4 | 8 | 4. 3 | 6. 7 | 2 | 8 | | | " | 171- 176 | 8 | 2. 4. 3 | 7. 6 | 6. 5* | 8. 7 | 3. 2* | | | | | 1 | 5 | 3 |13 | 1: 4. 33 7 | 177- 180 | | | | | | | 5. 4 | 8 | 4. 4. 3 | 8. 7 | 1 | 3 | | | " | 181- 190 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 3. 2. 5. 4 | 8 | 4. 3 | 7 | 4 | 6 | 5 | 9 | 1: 1. 80 8 | 191- 200 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 2 | 8 | | | " | 201- 210 | 8 | 4. 3 | 6 | 6. 4. 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 4 | 6 | 6 |14 | 1: 2. 33 9 | 211- 220 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 6. 7 | 2 | 8 | | | " | 221- 230 | 9. 8 | 4. 3 | 7. 6 | 6. 5 | 6. 7 | 3. 2 | 5. 4 | 7. 6. 8 | 4. 3 | 7 | 1 | 9 | 3 |17 | 1: 5. 67 | | | | | | | | | | | | | | | | 10 | 231- 240 | 8 | 4. 3 | 7. 6 | 6. 5 | 6. 7 | 3. 2 | 5. 4 | {3. 2. 3. 2. 4. 3 | 4. 3 | 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | | | | | {2. 5. 4. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | 11 | 241- 250 | 8 | 4. 3 | 7. 6 | 6. 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | | | | | | | | | | | | 12 | 251- 260 | 8 | 4. 3 | 6 | 6. 5 | 6. 7 | 3. 3. 2 | 5. 4 | {7. 6. 7. 7 | 3 | 3. 7* | 3 | 7 | 3 | 7 | 1: 2. 33 | | | | | | | | | {6. 9. 8* | | | | | | | | | | | | | | | | | | | | | | | 14 | 261- 270 | 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | {5. 3. 4. 3 | 3 | {3. 3. 3. 3. 4 | 5 | 5 | 5 | 5 | 1: 1. 00 | | | | | | | | | {9. 8* | | {4. 6. 4. 7* | | | | | | | | | | | | | | | | | | | | | 15 | 271- 280 | 7. 9. 8 | 4. 2. 3 | 3. 4. 3. 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 1 | 9 | | | " | 281- 290 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 7 | 3 | 7 | 4 |16 | 1: 4. 00 | | | | | | | | | | | | | | | | | | | | | | | | | {4. 3. 2. 3 | | | | | | | 16 | 291- 300 | 7. 8 | {4. 4. 4 | 6 | 6. 5 | 7 | 3. 3. 2 | 5. 4 | {6. 5. 4. 3 | 4. 3 | 6. 7 | 2 | 8 | | | | | | {4. 4. 3 | | | | | | {5. 6. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 301- 310 | 8 | 4. 4. 3 | 7. 6 | 6. 5 | 7 | 3. 3. 2 | 5. 5. 4 | {7. 6. 5. 4. 6 | 4. 3 | 7 | 3 | 7 | 5 |15 | 1: 3. 00 | | | | | | | | | {5. 7. 9. 8 | | | | | | | | | | | | | | | | | | | | | | | 17 | 311- 320 | 7. 8 | 4. 3 | 7. 6 | 6. 6. 5 | 7 | 3. 2 | 5. 4 | 7. 6. 7. 6. 7. 8 | 4. 3 | 7 | 2 | 8 | | | " | 321- 330 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 6. 7 | 2 | 8 | 4 |16 | 1: 4. 00 18 | 331- 340 | 7. 7. 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 4 | 6 | | | " | 341- 350 | 8 | 4. 3 | 7. 6 | 6. 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | 7 |13 | 1: 1. 86 19 | 351- 360 | 8 | 4. 3 | 7. 6 | 6. 5 | 6. 5. 6. 5. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | | | " | 361- 370 | 8 | 4. 3 | 7. 6 | 6. 4. 3. 6. 5 | 7 | 3. 2 | 5. 4 | 9. 8 | 4. 3 | 7 | 3 | 7 | 6 |14 | 1: 2. 33 21 | 371- 380 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 8. 7 | 2 | 8 | | | " | 381- 390 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 4 | 6 | 6 |14 | 1: 2. 33 22 | 391- 400 | 8 | 4. 3 | 7. 6 | 6. 5 | 6. 5. 4. 6. 7 | 3. 3. 3. 2 | 5. 4 | 6. 7. 8 | 4. 4. 3 | 7 | 2 | 8 | | | " | 401- 410 | 8 | 3 | 7. 6 | 6. 5 | 8. 7 | 2 | 5. 4 | 6. 7. 7. 8 | 3 | 7 | 5 | 5 | 7 |13 | 1: 1. 86 | | | | | | | | | | | | | | | | 23 | 411- 420 | 8 | 4. 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | {7. 6. 7. 6 | 4. 3 | 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | | | | | {6. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | 24 | 421- 430 | 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 7 | 6 | 4 | | | " | 431- 440 | 8 | 3 | 7. 6 | 6. 5 | 7 | 3. 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 5 | 5 |11 | 9 | 1: 0. 82 25 | 441- 450 | 7. 8 | 4. 4. 3 | 7. 6 | 6. 5 | 6. 5. 7 | 3. 3. 2 | 5. 5. 4 | 7. 8 | 4. 3 | 7 | 1 | 9 | 1 | 9 | 1: 9. 00 26 | 451- 460 | 7. 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | | | " | 461- 470 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 3 | 7 | 6 |14 | 1: 2. 33 28 | 471- 480 | 8 | 4. 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 9. 8 | 3 | 8. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 29 | 481- 490 | 8 | 4. 3 | 7. 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 30 | 491- 500 | 7. 9. 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | | | " | 501- 510 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 4. 3 | 8. 7 | 2 | 8 | 5 |15 | 1: 3. 00 July | | | | | | | | | | | | | | | | 1 | 511- 520 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | | | | | | | | 2 | 521- 530 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | {7. 6. 5. 6. 5 | 4. 4. 3 | 7 | 3 | 7 | | | | | | | | | | | | {6. 5. 6. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 531- 540 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 4 | 6 | 7 |13 | 1: 1. 86 3 | 541- 550 | 7. 8 | 4. 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 5. 5. 7 | 3 | 7 | | | " | 551- 560 | 7. 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 7 | 5 | 5 | 8 |12 | 1: 1. 50 5 | 561- 570 | 7. 7. 8 | 4. 3 | 6 | 6. 5 | 6. 7 | 3. 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | | | " | 571- 580 | 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 7 | 4 | 6 | 7 |13 | 1: 1. 86 | | | | | | | | | | | | | | | | | | | | | | {6. 5. 4. 6. 5 | | | | | | | | | | 6 | 581- 590 | 7. 8 | 4. 3 | 7. 6 | 6. 6. 5 | {5. 4. 5. 4. 4 | 2 | 3. 4 | 6. 5. 4. 3. 7. 8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2. 33 | | | | | | {6. 5. 6. 5. 8. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | 7 | 591- 600 | 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 8. 7 | 3 | 7 | | | " | 601- 610 | 7. 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 1 | 9 | 4 |16 | 1: 4. 00 8 | 611- 620 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 2 | 8 | | | " | 621- 630 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 9. 8 | 4. 3 | 8. 7 | 1 | 9 | | | " | 631- 640 | 8 | 4. 4. 3 | 7. 7. 6 | 6. 5 | 8. 7 | 3. 2 | 4 | 8 | 4. 3 | 8. 7 | 3 | 7 | 6 |24 | 1: 4. 00 | | | | | | | | | | | | | | | | 9 | 641- 650 | 7. 8 | 4. 3 | 7. 6 | 6. 5 | 6. 7 | 3. 2 | {3. 2. 5. 3 | 7. 6. 5. 4. 8 | 3 | 8. 7 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | | | | {2. 5. 4 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {6. 5. 4. 3. 7 | | | | | | | 10 | 651- 660 | 7. 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | {6. 5. 4. 7. 6 | 4. 3 | 7 | 3 | 7 | | | | | | | | | | | | {5. 4. 8 | | | | | | | | | | | | | | | | | | | | | | | 10 | 661- 670 | 8 | 3 | 7. 6 | 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 8. 7 | 6 | 4 | 9 |11 | 1: 1. 22 12 | 671- 680 | 7. 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 6. 5. 4. 7. 8 | 4. 3 | 8. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 | | | | | | | | | | | | | | | | 13 | 681- 690 | 8 | 3 | 7. 6 | 6. 5 | {6. 5. 4 | 3. 2 | 4 | 6. 7. 8 | 3 | {6. 5. 4. 5 | 4 | 6 | | | | | | | | | {6. 5. 7 | | | | | {6. 5. 8. 7 | | | | | | | | | | | | | | | | | | | | | " | 691- 700 | 8 | 3 | 6 | 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 7 | 8 | 2 |12 | 8 | 1: 0. 67 | | | | | | | | | | | | | | | | 14 | 701- 710 | 8 | 3 | 7. 6 | 6. 5 | {6. 5. 4. 5 | 2 | 3. 5. 4 | 8 | 3 | 7 | 6 | 4 | | | | | | | | | {4. 6. 8. 7 | | | | | | | | | | " | 711- 720 | 8 | 3 | 6 | 5 | 7 | 2 | 5. 4 | 6. 5. 4. 8 | 3 | 6. 5. 7 | 7 | 3 |13 | 7 | 1: 0. 54 15 | 721- 730 | 7. 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 5 | 5 | | | " | 731- 740 | 8 | 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 7 | 6 | 4 |11 | 9 | 1: 0. 82 16 | 741- 750 | 7. 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 4 | 8 | 3 | 7 | 7 | 3 | | | " | 751- 760 | 7. 8 | 3 | 7. 6 | 6. 5 | 7 | 2 | 4 | 7. 8 | 4. 3 | 7 | 5 | 5 |12 | 8 | 1: 0. 67 17 | 761- 770 | 8 | 4. 3 | 6 | 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4 | 7 | 6 | 4 | | | " | 771- 780 | 8 | 2. 2. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 7 | 3 | 7 | 9 |11 | 1: 1. 22 19 | 781- 790 | 8 | 3 | 7. 6 | 5 | 7 | 3. 2 | 3. 4 | 7. 6. 5. 8 | 3 | 7 | 6 | 4 | | | " | 791- 800 | 7. 8 | 3 | 6 | 5 | 7 | 2 | 5. 4 | 8 | 3 | 6. 5. 6. 7 | 7 | 3 | | | " | 801- 810 | 8 | 2. 3 | 6 | 5 | 6. 5. 7 | 2 | 5. 4 | 8 | 3 | 7 | 7 | 3 |20 |10 | 1: 0. 50 20 | 811- 820 | 7. 8 | 3 | 7. 6 | 5 | 7 | 3. 3. 2 | 5. 4 | 8 | 2. 2. 3 | 7 | 5 | 5 | | | " | 821- 830 | 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 4 | 8 | 2. 3 | 8. 7 | 6 | 4 |11 | 9 | 1: 0. 82 21 | 831- 840 | 8 | 3 | 5. 4. 5. 6 | 5 | 7 | 2 | 4 | 6. 7. 8 | 3 | 8. 7 | 7 | 3 | | | " | 841- 850 | 8 | 3 | 7. 6 | 5 | 7 | 3. 2 | 3. 2. 4 | 8 | 3 | 7 | 7 | 3 |14 | 6 | 1: 0. 43 22 | 851- 860 | 8 | 4. 3 | 6 | 5 | 7 | 3. 2 | 3. 5. 4 | 8 | 3 | 8. 7 | 6 | 4 | | | " | 861- 870 | 7. 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 4 | 8 | 3 | 8. 7 | 3 | 7 | | | " | 871- 880 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 2 | 8 |11 |19 | 1: 1. 73 23 | 881- 890 | 8 | 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 3 | 8. 7 | 4 | 6 | | | " | 891- 900 | 8 | 3 | 7. 6 | 6. 5 | 7 | 3. 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 5 | 5 | 9 |11 | 1: 1. 22 24 | 901- 910 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 8. 7 | 4 | 6 | | | " | 911- 920 | 8 | 3 | 7. 6 | 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0. 82 26 | 921- 930 | 7. 8 | 3 | 7. 6 | 5 | 7 | 3. 2 | 5. 4 | 8 | 2. 2. 3 | 8. 7 | 4 | 6 | | | " | 931- 940 | 8 | 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 5. 4 | 8 | 4. 3 | 8. 7 | 3 | 7 | 7 |13 | 1: 1. 86 27 | 941- 950 | 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0. 43 28 | 951- 960 | 8 | 3 | 7. 6 | 6. 5 | 5. 4. 7 | 2 | 5. 5. 4 | 8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0. 67 29 | 961- 970 | 8 | 3 | 7. 6 | 5 | 8. 7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0. 25 | | | | | | | | | | | | | | | | 30 | 971- 980 | 8 | 3 | 4. 3. 2. 6 | 5 | {6. 5. 4. 6 | 2 | 5. 5. 4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0. 43 | | | | | | {6. 5. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | 31 | 981- 990 | 8 | 3 | 6 | 6. 5 | 8. 7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0. 25 August | | | | | | | | | | | | | | | | 2 | 991-1000 | 8 | 3 | 7. 6 | 5 | 7 | 2 | {2. 3. 5. 3 | 7. 6. 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0. 43 | | | | | | | | {2. 3. 3. 4 | | | | | | | | | | | | | | | | | | | | | | | | 3 | 1001-1010 | 8 | 3 | 7. 6 | 5 | 7 | 2 | 4 | 7. 6. 5. 6. 7. 8 | 3 | 5. 4. 3. 4. 3. 7 | 7 | 3 | | | " | 1011-1020 | 8 | 2. 3 | 5. 6 | 3. 2. 3. 6. 5 | 7 | 2 | 5. 4 | 9. 8 | 2. 1. 3 | 7 | 4 | 6 |11 | 9 | 1: 0. 82 | | | | | | | | | | | | | | | | 4 | 1021-1030 | 7. 8 | 3 | 5. 4. 3. 7. 6 | 6. 5 | {6. 5. 6 | 3. 2 | 5. 4 | 8 | {2. 2. 4. 2 | 8. 7 | 2 | 8 | | | | | | | | | {5. 6. 7 | | | | {4. 2. 3 | | | | | | | | | | | | | | | | | | | | | | " | 1031-1040 | 7. 8 | 3 | 6 | 6. 4. 3. 6. 5 | 7 | 2 | 3. 5. 4 | 8 | 2. 3 | 8. 7 | 5 | 5 | 7 |13 | 1: 1. 86 | | | | | | | | | | | | | | | | 5 | 1041-1050 | 8 | 3 | 6 | 2. 3. 2. 6. 5 | 8. 7 | 2 | 4 | 8 | 2. 2. 4. 3 | {8. 8. 6. 8. 4 | 6 | 4 | 6 | 4 | 1: 0. 67 | | | | | | | | | | | {6. 5. 8. 7 | | | | | | | | | | | | | | | | | | | | | 6 | 1051-1060 | 8 | 3 | 6 | 4. 2. 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 8. 7 | 6 | 4 | 6 | 4 | 1: 0. 67 | | | | | | | | | | | | | | | | 7 | 1061-1070 | 8 | 3 | 5. 4. 3. 6 | 4. 5 | {6. 5. 6. 5 | 2 | 4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0. 43 | | | | | | {4. 8. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | 9 | 1071-1080 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0. 00--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | 1. 2. 3. 4. 5 | | | | | | 1. 2. 3. 4 | 2. 3. 4. 5 | | | | | | | 5. 6. 7. 8 | 2. 3. 4. 5. 6 | 6. 7. 8. 9 | 5. 6. 7 | 1. 2. 3. 4 | 4. 5. 6 | 2. 3. 4. 5 | 1. 2. 3 | 5. 6. 7 | 6. 7. 8. 9 | | | | |--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- 10 | 1- 10 | 6. 5. 7 | 3. 2. 6. 5 | 8 | 6 | 2. 4. 3 | 5 | 5. 4 | 2 | 7. 5. 2. 7. 6 | 8 | 5 | 5 | 5 | 5 | 1: 1. 00 11 | 11- 20 | 7 | 3. 6. 5 | 8 | 6 | 3 | 6. 5 | 4 | 3. 2 | 7. 6 | 8 | 6 | 4 | 6 | 4 | 1: 0. 67 | | | | | | | | | | | | | | | | | | | | | | | | {3. 2. 3. 5. 3 | | | | | | | | 12 | 21- 30 | 7 | 2. 2. 6. 5 | 7. 8 | 6 | 3 | 5 | {2. 5. 3. 2 | 2 | 6 | 8 | 7 | 3 | 7 | 3 | 1: 0. 43 | | | | | | | | {5. 3. 2. 5 | | | | | | | | | | | | | | | | {2. 5. 5. 4 | | | | | | | | | | | | | | | | | | | | | | | |========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

[Footnote 1: First choices correct by reason of aid from the experimenterare not counted as correct (R) in the summary. ]

[Footnote *: Aided by experimenter. ]

The method of choosing the first box at the right end and then the onenext to it developed in the case of all except two of the ten settings. The time of appearance is worth noting. In setting 1, it failed toappear; in setting 2, it developed early, --after about one hundredtrials; in setting 3, after about one hundred and fifty trials; insetting 4, after about one hundred and fifty trials; in setting 5, afterabout one hundred and seventy trials; in setting 6, after about onehundred trials; in setting 7, after about fifty trials; in setting 8, itnever developed; in setting 9, after about fifty trials; and in setting10, it developed very late, --after about four hundred and seventytrials. 

This method of reaction, although inadequate, proved remarkablypersistent, and it is doubtful whether it had been wholly overcome atthe conclusion of the experiment. In the case of the series of trialsgiven on June 8, numbered 191 to 200, the method used was either that ofthe first at the right and then the next, or direct choice of the rightbox. 

Throughout the trials with this problem, the end boxes, numbers 1 and 9, were avoided. This is at least partially explained by the fact that theynever existed, and obviously never could appear, in problem 2, as rightboxes. In trials 601 to 610, given on July 7, there occurred partialreturn to the formerly established method of choosing the first door atthe right. This relapse was characteristic of what happened during themany days which intervened between the definite appearance of this habitand the final solution of the problem. 

Especially in connection with such relapses, Skirrl showed extremefatigue or ennui and often would refuse to work and simply sit beforethe open doors yawning. This happened even when he was extremely hungryand evidently eager enough for food. 

From July 12 on the hunger motive was increased by feeding the monkeyonly in the apparatus and by so regulating the amount of food given ineach trial that he should obtain barely enough to keep him in goodphysical condition. An increase in the number of correct choicespromptly resulted, and continued until on July 14 the ratio of choiceswas 1 to . 54. It appeared from these data that a relatively small numberof choices, say not more than ten a day, the rewards in connection withwhich supplied the only food received by the animal, yielded mostfavorable results. 

On July 16, the period of confinement in wrong boxes was increased tosixty seconds, and it was so continued for a number of days. But in theend, it became clear that the period of thirty seconds, combined with aliberal reward in the shape of desired food and a single series of tentrials per day, was most satisfactory. The detailed data of table 2indicate that at this time Skirrl was making his choices by memory ofthe particular setting. 

Skirrl, on July 17 was evidently hungry and eager to locate food, butseemingly unable to select the right box. In trial 5 (765th) of theseries, he was punished by confinement in box 8. When the doors wereunlocked in order that the entrance door might be raised to release him, the lock-bar, sliding under the floor, made a slight grating noise, andthe instant the entrance door was opened, he jumped out excitedly. _Hemade no outcry, but as soon as he was out of the box, sat down, andtaking up his right hind foot, examined it for a few seconds. _ Havingapparently assured himself that nothing serious had happened, he went onunconcernedly about his task. The presumption is that the sound of thelock-bar, associated as it was with his painful experience in box 1, revived the strongly affective experience of stepping on the nail. Psychologically described, the sound induced an imaginal complexequivalent to the earlier painful experience. The behavior seems to thewriter a most important bit of evidence of imagery in the monkey. Finally, on August 9, after ten hundred and seventy trials, Skirrlsucceeded in choosing correctly in the ten trials of a series, and hewas therefore considered to have solved the problem of the second doorfrom the right end of the group. 

On the following day, he was given a control series with the settingswhich are presented on page 19 and also at the bottom of table 2. Inthis series he chose correctly five times, --in other words, as oftencorrectly as incorrectly. An analysis of the choices indicates, however, that two of the five correct choices were made in box 8, which, as ithappened, had proved a peculiarly easy one for him throughout thetraining, since from the first he tended to avoid door 9. Consequently, it is only fair to conclude, from the results for this control seriesand for those given on August 11 and 12, that the animal chose not onthe basis of anything remotely resembling a general idea of secondnessfrom the right end, but instead on the basis of gradually acquired modesof reaction to the particular settings. This conclusion is strengthenedby the fact that he had failed to learn to react appropriately andreadily to most of the settings of the regular series. 

The curve which represents the course of the learning process in thisproblem is presented in figure 19. For this and all other curves whichinvolve more than a single series of observations a day, the method ofconstruction was as follows: The first series for each day of trainingis indicated on the curve by a dot, while the second or third series ona given day, although space is allowed for them, are not so indicated. Consequently, the form of the curve is determined chiefly by the firstseries per day. The extreme irregularities of this curve are mostinteresting and puzzling, as are also the variations in the daily ratiosof right to wrong first choices. Three times in the course of thetraining, this ratio rose to 1 to 9, or higher. The causes for suchextreme variations are not easily enumerated, but a few of the mostobvious contributory causes are variations in the weather, especiallycloudiness or fogginess, which rendered the apparatus dark; variationsin the degree of hunger or eagerness for food; differences in theactivities of the animals in the cages outside of the laboratory(sometimes they were noisy and distracted the subject), and finally, differences in the physical fitness and attitude of the animal from dayto day. 

The more or less incidental behavior in connection with this experimentmore strongly than the statistical results of the work on problem 2indicate the existence of imagery. That ideas played a part in thesolution of the problem is probable, but at best they functioned veryineffectively. The small number of methods used in the selection of theright box, and the slight variations from the chief method, that ofchoosing the first box at the right end and then the one next to it, apparently justify Doctor Hamilton's characterization of this monkey asdefective. 

[Illustration: FIGURE 19. --Error curves of learning for the solution ofproblem 2 (second box from right end). ]

_Problem 3. Alternately First at Left and First at Right_

Following the control series given in connection with problem 1, aninterval of rest lasting from August 12 to August 19 was allowed inorder that Skirrl might in part at least lose the effects of histraining and regain his customary interest in the apparatus by beingallowed to obtain food easily instead of by dint of hard labor, --laborwhich was harder by far, apparently, than physical activity because itdemanded of the animal certain mental processes which were eitherlacking or but imperfectly functional. The difficultness of the dailytasks appears to be reliably indicated by the tendency to yawn. 

Systematic work on problem 3, which has been defined as alternately thefirst door at the left and the first door at the right of the group, wasbegun August 19, and for nine days a single series of ten trials per daywas given. Work then had to cease because of the experimenter's returnto Cambridge. 

The results of the work on this problem demand but brief analysis andcomment. The expected ratio of one right to four wrong choices perseries appears (see table 3) for the first series of trials, and _thisin spite of the fact that Skirrl had been trained for several weeks tochoose the second door from the right end_. One would ordinarily havepredicted a much larger number of incorrect choices. The right choiceswere due to the monkey's strong tendency to go first to the first doorat the right and thence to the one next to it. Indeed in the seriesgiven on August 24; this method was followed without variation. In otherwords, in every one of the ten trials Skirrl entered first the box atthe extreme right end of the group. This necessarily resulted in as manyright as wrong first choices. Consequently, the ratio reads 1 to 1. Butthe method was not adhered to, and at no time either before or afterthat date did he succeed in equalling this achievement. There was, as amatter of fact, no steady improvement, and so far as one may judge fromthe records which were obtained, the course of events in the solution ofthis problem would have been similar to those in problem 2. 

TABLE 3

Results for Skirrl, _P. Irus_, in Problem 3

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== Date | No. Of | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | R | W | R | W |Ratio of | trials | 5. 6. 7 | 5. 6. 7 | 1. 2. 3. 4. 5. 6 | 1. 2. 3. 4. 5. 6 | 4. 5. 6. 7. 8 | 4. 5. 6. 7. 8 | 2. 3. 4. 5 | 2. 3. 4. 5 | 3. 4. 5. 6. 7. 8. 9| 3. 4. 5. 6. 7. 8. 9| | | | |R to W________|___________|______________|______________|______________|______________|______________|______________|______________|______________|______________|______________|___|___|___|___|________August | | | | | | | | | | | | | | | | | | | | {6. 5. 4. 6 | | | | | | | {8. 7. 6. 5 | | | | | 19 | 1- 10 | 7. 5 | 6. 7 | {3. 2. 6. 4 | 5. 3. 6 | {7. 8. 7. 6 | 8 | 4. 3. 5. 4. 5. 2 | 5 | 9. 8. 7. 6. 4. 3 | {4. 5. 8. 7 | 2 | 8 | 2 | 8 | 1:4. 00 | | | | {3. 6. 1* | | {8. 6. 4 | | | | | {6. 5. 9* | | | | | | | | | | | | | | | | | | | | | | | | | {5. 4. 6. 5 | | {8. 7. 6. 7 | | | | | | | | | | 20 | 11- 20 | 7. 6. 5 | {6. 5. 6. 5 | {4. 6. 5. 3 | 5. 3. 2. 4. 6 | {7. 5. 8. 8 | 8 | 5. 4. 3. 2 | 4. 5 | 8. 7. 6. 5. 4. 3 | {8. 7. 6. 8. 3 | 1 | 9 | 1 | 9 | 1:9. 00 | | | {7 | {2. 5. 1* | | {7. 6. 4* | | | | | {7. 6. 4. 3. 9 | | | | | | | | | | | | | | | | | | | | | | | | | {6. 2. 5. 6 | | | | {5. 3. 5. 4 | | | | | | | | 21 | 21- 30 | 7. 6. 7. 6. 5 | 7 | {5. 3. 6. 5 | 2. 5. 5. 6 | 8. 6. 5. 4 | 8 | {3. 5. 3. 5 | 5 | {9. 8. 7. 6 | 8. 9 | 3 | 7 | 3 | 7 | 1:2. 33 | | | | {4. 3. 1* | | | | {4. 3. 2* | | {5. 4. 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 23 | 31- 40 | 7. 6. 5 | 6. 5. 7 | {6. 4. 3. 2 | 3. 2. 6 | 8. 7. 6. 4 | 8 | 5. 4. 5. 3. 2 | 5. 2 | 8. 7. 3 | 9 | 2 | 8 | 2 | 8 | 1:4. 00 | | | | {5. 6. 2. 1 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 24 | 41- 50 | 7. 6. 5 | 7 | {6. 2. 5 | 6 | {8. 7. 8. 7 | 8 | 5. 3. 2 | 5 | {9. 8. 7. 6 | 9 | 5 | 5 | 5 | 5 | 1:1. 00 | | | | {4. 3. 1 | | {5. 7. 5. 4 | | | | {5. 4. 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {8. 7. 3. 6 | | | | | 25 | 51- 60 | 7. 6. 5 | 6. 5. 7 | 5. 2. 1 | 6 | 8. 5. 4 | 8 | 2 | 2. 5 | 9. 8. 7. 4. 3 | {8. 7. 5. 3 | 3 | 7 | 3 | 7 | 1:2. 33 | | | | | | | | | | | {8. 7. 9* | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 26 | 61- 70 | 7. 6. 5 | 6. 5. 7 | 1 | 2. 1. 6 | 8. 7. 6. 4 | 8 | 2 | 3. 2. 5 | 9. 8. 7. 5. 3 | {3. 6. 8. 3 | 3 | 7 | 3 | 7 | 1:2. 33 | | | | | | | | | | | {4. 7. 9 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {8. 6. 3. 3 | | | | | 27 | 71- 80 | 7. 6. 5 | 7 | 2. 1 | 1. 5. 6 | 8. 7. 6. 4 | 8 | 2 | 5 | 9. 8. 7. 6. 3 | {7. 5. 3. 8 | 4 | 6 | 4 | 6 | 1:1. 50 | | | | | | | | | | | {3. 6. 9* | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 28 | 81- 90 | 7. 6. 7. 5 | 7 | 3. 1 | 6 | 8. 6. 4 | 4. 8 | 2 | 2. 4. 5 | 8. 7. 4. 3 | 3. 8. 9 | 3 | 7 | 3 | 7 | 1:2. 33 | | | | | | | | | | | | | | | |========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

[Footnote *: Aided by experimenter. ]

2. Sobke, _Pithecus rhesus_

_Problem 1. First at the Left End_

Sobke was somewhat afraid of the experimenter when the investigation wasundertaken, and instead of willingly coming out of his cage when thedoor was raised, he often had to be coaxed out and lured into theapparatus with food. Whereas Skirrl was frank and rather aggressive, Sobke was stealthy in his movements, furtive, and evidently suspiciousof the experimenter as well as of the apparatus. He was perfectly safeto approach, but would not permit anyone to touch him. After a few days, he began to take food from the hands of the experimenter. 

Preliminary work to acquaint this monkey with the routine of theexperiment was begun on April 13. As in the case of Skirrl, he was luredinto the apparatus and was taught the route through the boxes to thestarting point by being allowed to obtain food once each day in each ofthe nine boxes. The procedure was simple. The entrance door and the exitdoor of a particular box were raised and the animal admitted to thereaction-compartment and permitted to pass through the box whose doorsstood open, take its food, and return to the starting point. Sobke veryquickly learned the route perfectly and came to work steadily andrapidly. After five days of preliminary work of this sort, he was sothoroughly accustomed to the apparatus that it was evidently desirableto begin with regular training experiments. 

The first series of trials was given on April 19. Both punishment andreward were employed from the first. The punishment consisted ofconfinement for thirty seconds in each wrong box, and the reward of asmall piece of banana, usually not more than a tenth of a medium sizedbanana for each correct choice. The total time for the first series oftrials was fourteen minutes. This indicates that Sobke worked rapidly. My notes record that he worked quickly though shyly, wasted almost notime, made few errors of choice, and waited quietly during confinementin the boxes. In this, also, he differed radically from Skirrl who wasrestless and always tried to escape from confinement. 

Throughout the work on problem 1, punishment and reward were keptconstant. Everything progressed smoothly; there were no suchirregularities of behavior as appeared in the case of Skirrl, andconsequently the description of results is a relatively simple matter. Sobke invariably chose the end boxes. His performance was in every waysuperior to that of Skirrl. 

As previously, the detailed results are presented in tabular form (table4). From this table it appears that, whereas the expected ratio of rightto wrong first choices for this problem is 1 to 2. 5, the actual ratiofor Sobke's first series was 1 to . 67. This surprisingly good showing isunquestionably due to his marked tendency to choose the end box of agroup; and this tendency, in turn, may in part be the result of thepreliminary training, for during that only one box was open each time. But, if the preliminary training were responsible for Sobke's tendency, it should be noted that it had very different effect upon Skirrl, and, as will be seen later, upon Julius. 

The results for the ten different settings of the doors for problem 1 asthey appear in table 4 are of interest for a number of reasons. In thefirst place, the setting 1. 2. 3 appearing twice, --at the beginning ofthe series and again at the end--yielded markedly different results inthe two positions. For whereas no mistakes were made in the case ofsetting 1, there were fifty per cent of incorrect first choices forsetting 10. Again, satisfactory explanation is impossible. It isconceivable that fatigue or approaching satiety may have had somethingto do with the failures at the end of the series, but as a rule, as isindicated by settings 1, 2, and 6, if correct choices were made at thebeginning, they continued throughout the day's work. 

In this problem, Sobke's improvement was steady and fairly rapid, and inthe eighth series, trials 71 to 80, only correct first choices appear. Consequently, seventy trials were required for the solution of theproblem. This number is in marked contrast with Skirrl's one hundred andthirty-two trials. 

Immediately following the first perfect series, Sobke was given twoseries of control tests on April 28. Conditions were unfavorable, sincethe day was stormy and the rain pattering on the sheet-iron roof made agreat din. Nevertheless, he worked steadily and well up to the sixthtrial, which was preceded by a slight delay because of the necessity ofrefilling some of the food boxes. After this interruption, wrong choicesoccurred in trial 6. And again after trial 9, there was briefinterruption, followed by wrong choices in trial 10. The ratio of rightto wrong choices for this first control series was therefore 1 to . 25. 

TABLE 4

Results for Sobke, _P. Rhesus_, in Problem 1

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | | | | | | | | | R | W | R | W | of | trials | 1. 2. 3 | 8. 9 | 3. 4. 5. 6. 7 | 7. 8. 9 | 2. 3. 4. 5. 6 | 6. 7. 8 | 5. 6. 7 | 4. 5. 6. 7. 8 | 7. 8. 9 | 1. 2. 3 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- April | | | | | | | | | | | | | | | | 19 | 1-10 | 1 | 8 | 3 | 9. 7 | 6. 2 | 6 | 7. 5 | 4 | 9. 7 | 1 | 6 | 4 | 6 | 4 | 1:0. 67 20 | 11-20 | 1 | 8 | 3 | 7 | 2 | 6 | 7. 5 | 8. 4 | 9. 9. 7 | 1 | 7 | 3 | 7 | 3 | 1:0. 43 21 | 21-30 | 1 | 8 | 4. 3 | 9. 7 | 2 | 6 | 5 | 8. 4 | 7 | 1 | 7 | 3 | 7 | 3 | 1:0. 43 22 | 31-40 | 1 | 8 | 3 | 7 | 6. 2 | 6 | 6. 5 | 4 | 7 | 3. 1 | 7 | 3 | 7 | 3 | 1:0. 43 23 | 41-50 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 9. 7 | 3. 1 | 8 | 2 | 8 | 2 | 1:0. 25 24 | 51-60 | 1 | 8 | 3 | 9. 7 | 2 | 6 | 5 | 4 | 7 | 2. 1 | 8 | 2 | 8 | 2 | 1:0. 25 26 | 61-70 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 3. 1 | 9 | 1 | 9 | 1 | 1:0. 11 27 | 71-80 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0. 00--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | 2. 3. 4 | | | 1. 2. 3. 4. 5 | | | | | | | 2. 3. 4 | 6. 7. 8. 9 | 3. 4. 5 | 4. 5. 6. 7. 8. 9 | 6. 7. 8. 9 | 1. 2. 3. 4. 5 | 5. 6. 7. 8 | 3. 4. 5. 6. 7. 8 | 5. 6. 7 | 6. 7. 8. 9 | | | | | | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | | | | 28 | 1-10 | 2 | 6 | 3 | 4 | 6 | 5. 4. 1 | 2 | 3 | 5 | 5. 4. 2. 1 | 8 | 2 | | | " | 11-20 | 2 | 6 | 3 | 4 | 6 | 2. 1 | 2 | 3 | 5 | 1 | 9 | 1 |17 | 3 | 1:0. 18 | | | | | | | | | | | | | | | |========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

Six minutes after completion of the first control series, a second wasgiven under slightly more favorable conditions, and in this only asingle wrong choice occurred, in that box 2 was first chosen in trial 6instead of box 1. From the results of these two control series, it isevident that Sobke's solution of problem 1 is reasonably adequate. He iseasily diverted or disturbed in his work by any unusual circumstances, but so long as everything goes smoothly, he chooses with ease andcertainty. Whether it is fair to describe the behavior as involving anidea of the relation of the right box to the other members of the groupwould be difficult to decide. I hesitate to infer definite ideation fromthe available evidence, but I strongly suspect the presence of imagesand relatively ineffective or inadequate ideation. 

It is perfectly evident that Sobke is much more intelligent than Skirrl. In practically every respect, he adapted himself more quickly to theexperimental procedure and progressed more steadily toward the solutionof the problem than did Skirrl. The contrast in the learning processesof the two monkeys could scarcely be better exhibited than by the curvesof learning which are presented in figure 18. The first, that for Sobke, is surprisingly regular; the second, that for Skirrl, is quite assurprisingly irregular. These results correlate perfectly with thesteadiness and predictability of the former's responses and theirregularity and erraticness of the latter's. 

_Problem 2. Second from the Right End_

On the completion of problem 1 Sobke was in perfect condition, as tohealth and training, for experimental work. He had come to work quietly, fairly deliberately, and very steadily. His timidity had diminished andhe would readily come to the experimenter for food, although still hewas somewhat distrustful at times and became timid when anything unusualoccurred in the apparatus. 

As preparation for problem 2, a break in regular experimentationcovering four days followed the control series of problem 1. On each ofthese four days the monkey was allowed to get food once from each of thenine boxes, both doors of a given box being open for the trial and allother doors closed. For this feeding experiment, the doors were openedin irregular order, and this order was changed from day to day. 

Systematic work with problem 2 began on May 3, with punishment of thirtyseconds for mistakes and a liberal reward of food for each success. Early in the series of trials it was discovered that Sobke was likely tobecome discouraged and waste a great deal of time unless certain aidwere given by the experimenter. On this account, after the first twotrials, the method was adopted of punishing the animal by confinementfor the first ten mistakes in a trial, and of then, if need be, indicating the right box by slightly and momentarily raising the exitdoor. Every trial in which aid was thus given by the experimenter isindicated in table 5 by an asterisk following the last choice. In thefirst series of trials for this problem, aid had to be given in seven ofthe ten trials, and even so the series occupied seventy-one minutes. Itis possible that had no aid been given, the work might have beencontinued successfully with a smaller number of trials than ten per day. But under the circumstances it seemed wiser to avoid the risk ofdiscouraging and thus spoiling the animal for use in the experiment. Itshould be stated, also, that it proved impossible to adhere to theperiod of thirty seconds as punishment in this series. For the majorityof the wrong choices confinement of not more than ten seconds was used. 

For the second series, given on May 4, the conditions were unfavorablein that it was dark and rainy, and the noise of the rain on the rooffrightened Sobke. He refused to work after the fourth trial, and theseries had to be completed on the following day. The total time requiredfor this series was seventy-eight minutes. 

The work on May 6 was distinctly better, and the animal's behaviorindicated, in a number of trials, definite recognition of the rightdoor. He might, for example, make a number of incorrect choices, thenpause for a few seconds to look steadily at the doors, and havingapparently found some cue, run directly to the right box. No aid fromthe experimenter was needed in this series. 

On the following day improvement continued and the animal's method ofchoosing became definite and fairly precise. He was deliberate, quiet, and extremely business-like. The time for the series was thirty-oneminutes. 

The period of punishment was increased on May 12 to thirty seconds. Previously, for the greater number of the trials, it had been ten tofifteen seconds. This increase apparently did not disturb the monkey, for he continued to work perfectly throughout the series, althoughmaking many mistakes in spite of deliberate choices and the refusal ofcertain boxes in each trial. 

An interesting and significant incident occurred on May 13 when at theconclusion of trial 5, Doctor Hamilton came into the experiment room fora few minutes. Sobke immediately stopped working, and he could not beinduced to make any choices until Doctor Hamilton had left the room. This well indicates his sensitiveness to his surroundings, and hisinclination to timidity or nervousness even in the presence ofconditions not in themselves startling. 

Work was continued thus steadily until May 28 when, because of thefailure of the animal to improve, it seemed wise to increase the periodof confinement as punishment to sixty seconds. In the meantime, it hadsometimes been evident that Sobke was near to the solution of hisproblem. He would often make correct choices in three or four trials insuccession and then apparently lose his cue and fail utterly for anumber of trials. 

After June 1, in order to hasten the solution of the problem, two seriesper day were given. In some instances the second series was given almostimmediately after the first, while in others an interval of an hour ormore intervened. It was further found desirable to give Sobke all of hisfood in the apparatus. When the rewards obtained in the several trialsdid not satisfy his hunger, additional food was presented, on thecompletion of the series of experiments, in one or more of the foodcups. On days marked by unwillingness or refusal to work, very littlefood was given. Thus, the eagerness of the monkey to locate the rightbox was increased and, as a matter of observation, his deliberatenessand care in choice increased correspondingly. Sixty seconds punishmentwas found satisfactory, and it was therefore continued throughout thework on this problem. 

It was evident, on June 9, from the behavior of the monkey as well asfrom the score, that the perfect solution of the problem was near athand. This fact the experimenter recorded in his daily notes, and sureenough, on the following day Sobke chose correctly throughout the seriesof ten trials. The time for this series was only ten minutes. Thechoices were made deliberately and readily. 

An analysis of the data of table 5 reveals five methods or reactivetendencies which appeared more or less definitely in the followingorder: (a) Choice of first box at the left, because of experience inproblem 1. This tendency was very quickly suppressed by the requirementsin connection with problem 2. Indeed one of the most significantdifferences which I have discovered between the behavior of the primatesand that of other mammals is the time required for the suppression ofsuch an acquired tendency. The monkey seems to learn almost immediatelythat it is not worth while to persist in a tendency which althoughpreviously profitable no longer yields satisfaction, whereas in thecrow, pig, rat, and ring dove, the unprofitable mode of response tendsto persist during a relatively large number of trials. (b) The tendencyto choose, first, a box near the left end of the group, to go from thatto the box at the extreme right end of the group, thence to the one nextin order, which was, of course, the right box. This tendency appearsfairly clearly from May 7th on. (c) The box at the extreme right wasfirst chosen and then the one next to it. For example, in setting 2, box4 would be chosen first, then box 3. Or, if this did not occur, themethod previously described under (b) was likely to be employed, as forexample, in setting 8, where such choices as 7. 6. 5. 1. 8 appear. (d) Incertain series there appeared a marked preference for a particular box, usually box 3 (see results for May 24). This was doubtless due in ameasure, if not wholly, to the fact that box 3 was the right box twicein each series of ten settings. But it should be added that the same istrue of box 7, for which no preference was manifested at any time. (e)Direct choice of the right box. 

The five reactive methods or tendencies enumerated above roughlyappeared in the order named, but there were certain irregularities andthe order as well as the time of appearance varied somewhat from settingto setting. In general, method c was the most frequently used prior tothe development of method e, the direct choice of the right box. 

TABLE 5

Results for Sobke, _P. Rhesus_, in Problem 2

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | | | | | | 1. 2. 3. 4. 5 | | | R | W | R | W | of | trials | 7. 8. 9 | 1. 2. 3. 4 | 2. 3. 4. 5. 6. 7 | 1. 2. 3. 4. 5. 6 | 4. 5. 6. 7. 8 | 1. 2. 3 | 2. 3. 4. 5 | 6. 7. 8. 9 | 1. 2. 3. 4 | 3. 4. 5. 6. 7. 8 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | May | | {7. 7. 9. 7. 7 | {1. 2. 4. 1 | {3. 2. 7. 2 | {4. 6. 1. 6 | | {3. 1. 3. 3 | | | {4. 1. 4. 1 | {3. 8. 3. 3 | | | | | 3 | 1-10 | {9. 7. 9. 7. 9 | {1. 4. 1. 1 | {7. 7. 7. 5 | {1. 6. 1. 1 | 5. 8. 6. 7 | {3. 3. 1. 1 | 3. 5. 4 | 9. 1. 8 | {4. 1. 4. 2 | {3. 8. 6. 3 | 0 |10 | 0 |10 | 0:10. 00 | | {7. 9. 9. 7. 8* | {4. 3* | {2. 7. 6* | {1. 3. 5* | | {1. 1. 2* | | | {1. 4. 3* | {8. 3. 7* | | | | | | | | | | | | | | | | | | | | | | | | | {4. 7. 2. 7 | | (8. 8. 4. 8 | | {5. 5. 5. 5 | {9. 5. 5. 9 | | | | | | |4 and 5 | 11-20 | (7. 9. 7. 9. 9 | 1. 4. 1. 3 | {2. 7. 3. 2 | 1. 6. 5 | {8. 8. 4. 8 | {3. 3. 1. 1. 3 | {5. 5. 5. 3 | {7. 1. 6. 6 | {4. 4. 4. 4 | {8. 8. 6. 8 | 0 |10 | 0 |10 | 0:10. 00 | | {9. 7. 7. 9. 8 | | {7. 2. 6* | | {4. 8. 7* | {3. 3. 1. 2 | {5. 5. 4* | {6. 5. 8* | {4. 4. 4. 3 | {8. 7 | | | | | | | | | | | | | | | | | | | | | 6 | 21-30 | 9. 7. 9. 7. 8 | 4. 3 | 7. 2. 3. 7. 6 | {6. 3. 1. 6 | 6. 8. 7 | 3. 1. 2 | {5. 3. 5. 3 | {6. 9. 4. 6. 1 | {4. 1. 2. 4 | {3. 4. 5. 3 | 0 |10 | 0 |10 | 0:10. 00 | | | | | {6. 2. 6. 5 | | | {2. 4 | {7. 9. 7. 8 | {4. 2. 3 | {8. 6. 7 | | | | | | | | | | | | | | | | | | | | | 7 | 31-40 | 7. 9. 7. 8 | 1. 4. 3 | 2. 7. 6 | 3. 5 | 4. 8. 7 | 3. 1. 2 | 3. 2. 3. 5. 4 | 8 | 4. 3 | 5. 8. 3. 4. 8. 7 | 1 | 9 | 1 | 9 | 1: 9. 00 8 | 41-50 | 7. 9. 7. 8 | (4. 2. 4. 1. 4 | 6 | 5 | 6. 5. 4. 8. 7 | {3. 1. 3. 1 | 5. 3. 5. 4 | {7. 4. 2. 1 | {4. 2. 4. 1 | 5. 3. 8. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | {4. 2. 2. 4. 3 | | | | {3. 1. 3. 2 | | {9. 8 | {4. 3 | | | | | | | | | | | | | | {5. 3. 5. 3 | | | | | | | | 10 | 51-60 | 7. 7. 8 | 3 | 7. 3. 2. 7. 6 | 6. 4. 6. 5 | (6. 4. 8. 5 | 3. 1. 3. 2 | {2. 5. 3. 5 | 5. 9. 8 | 4. 2. 4. 3 | {6. 5. 4 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | | {4. 8. 7 | | {2. 5. 4 | | | {3. 8. 7 | | | | | | | | | | | | | | | | | | | | | 11 | 61-70 | 7. 9. 7. 8 | 1. 4. 3 | 4. 3. 2. 7. 6 | 6. 5 | {5. 4. 8. 6 | 3. 2 | 5. 4 | 6. 5. 2. 3. 1. 8 | 3 | 6. 5. 3. 8. 7 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | | {5. 4. 8. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | 12 | 71-80 | 7. 9. 8 | 3 | 7. 3. 2. 7. 6 | 6. 5 | 5. 4. 8. 7 | 1. 2 | 5. 4 | 8 | 4. 3 | 5. 4. 3. 8. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 13 | 81-90 | 7. 8 | 4. 3 | 3. 7. 6 | 6. 5 | 8. 7 | 1. 3. 2 | 2. 5. 2. 5. 4 | 7. 6. 5. 9. 8 | 3 | 8. 7 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | | | | | | | | | | | | | | | | | | | | | | {1. 2. 1. 2. 2 | | | | | | 14 | 91-100 | 7. 8 | 3 | 6 | 5 | 6. 5. 4. 7 | 1. 3. 2 | 5. 4 | 9. 8 | {1. 4. 2. 2. 1 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | | {4. 1. 4. 3 | | | | | | | | | | | | | | | | | | | | | | 15 | 101-110 | 7. 8 | 3 | 7. 6 | 5 | 5. 4. 5. 7 | 3. 2 | 5. 4 | 8 | 2. 1. 3 | 8. 8. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 | | | | | | | | | | | | | | | | 17 | 111-120 | 7. 8 | 4. 3 | 7. 6 | {2. 1. 2. 1. 2 | 8. 7 | 3. 2 | 5. 4 | 7. 6. 5. 1. 8 | 3 | 8. 7 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | {1. 3. 2. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | 18 | 121-130 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 6. 5. 2. 8 | 3 | 8. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 | | | | | | | | | | | | | | | | | | | | | | | | {5. 3. 2. 5. 3 | | | | | | | | | | | | | | | | {2. 5. 2. 5. 3 | | | | | | | | 19 | 131-140 | 8 | 3 | 3. 2. 6 | 5 | 7 | 3. 2 | {5. 5. 2. 5. 5 | 7. 6. 9. 8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0. 67 | | | | | | | | {3. 2. 5. 5. 3 | | | | | | | | | | | | | | | | {2. 5. 5. 4 | | | | | | | | | | | | | | | | | | | | | | | | 20 | 141-150 | 7. 8 | 3 | 3. 2. 7. 6 | 6. 5 | 5. 4. 7 | 3. 2 | 3. 2. 5. 4 | 6. 5. 4. 3. 8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2. 33 21 | 151-160 | 7. 8 | 3 | 5. 7. 5. 3. 7. 6 | 5 | 7 | 3. 2 | 5. 3. 5. 2. 5. 4 | 7. 6. 5. 9. 8 | 3 | 6. 4. 3. 8. 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | | | | | | | | 22 | 161-170 | 7. 8 | 3 | 7. 6 | 3. 2. 6. 5 | 7 | 3. 2 | {5. 2. 5. 3 | 7. 6. 5. 8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | {2. 5. 4 | | | | | | | | | | | | | | | {3. 1. 3 | | | | | | | | | 24 | 171-180 | 8 | 3 | {3. 2. 7. 5 | {3. 6. 4 | 8. 7 | {1. 3. 3 | {3. 5. 4 | 8 | {4. 4. 2. 1 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | {7. 3. 6 | {3. 6. 5 | | {3. 2 | | | {4. 3 | | | | | | | | | | | | | | | | | | | | | | 25 | 181-190 | 7. 9. 7. 9. 8 | 3 | 3. 7. 6 | 5 | 8. 7 | 3. 2 | 5. 4 | 4. 3. 8 | 4. 3 | 8. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 26 | 191-200 | 8 | 3 | 6 | 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 5 | 5 | 5 | 5 | 1: 1. 00 27 | 201-210 | 7. 9. 8 | 3 | 3. 2. 7. 6 | 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 3 | 8. 7 | 4 | 6 | 4 | 6 | 1: 1. 50 28 | 211-220 | 8 | 3 | 3. 7. 6 | 4. 3. 2. 6. 5 | 8. 7 | 3. 2 | 5. 4 | 7. 6. 5. 9. 8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 29 | 221-230 | 7. 8 | 3 | 5. 4. 3. 7. 6 | 6. 5 | 7 | 2 | 3. 2. 5. 4 | 7. 6. 5. 8 | 3 | 3. 8. 7 | 4 | 6 | 4 | 6 | 1: 1. 50 31 | 231-240 | 7. 7. 8 | 3 | 3. 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 9. 8 | 3 | 3. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 June | | | | | | | | | | | | | | | | 1 | 241-250 | 8 | 3 | 5. 4. 7. 6 | 3. 2. 6. 5 | 8. 7 | 3. 2 | 5. 4 | 8 | 3 | 8. 7 | 4 | 6 | | | | | | | | | | | | | | | | | | | " | 251-260 | 7. 9. 8 | 3 | 3. 7. 6 | 5 | 6. 5. 4. 8. 7 | 3. 2 | 4 | 5. 4. 3. 8 | {4. 2. 1. 4 | 7 | 4 | 6 | 8 |12 | 1: 1. 50 | | | | | | | | | | {2. 4. 4. 3 | | | | | | | | | | | | | | | | | | | | | | 2 | 261-270 | 7. 8 | 3 | 6 | 3. 2. 6. 5 | 7 | 3. 2 | 3. 4 | 8 | 3 | 6. 5. 3. 8. 7 | 5 | 5 | | | " | 271-280 | 7. 8 | 3 | 3. 7. 6 | 3. 6. 5 | 7 | 3. 2 | 5. 4 | 7. 6. 5. 4. 3. 8 | 3 | 7 | 4 | 6 | 9 |11 | 1: 1. 22 3 | 281-290 | 7. 8 | 3 | 7. 6 | 3. 6. 5 | 8. 7 | 3. 2 | 4 | 7. 8 | 3 | 7 | 4 | 6 | | | " | 291-300 | 9. 8 | 3 | 3. 6 | 4. 3. 6. 5 | 8. 7 | 2 | 3. 5. 4 | 7. 6. 5. 9. 8 | 3 | 8. 7 | 3 | 7 | 7 |13 | 1: 1. 86 4 | 301-310 | 8 | 3 | 7. 6 | 3. 4. 3. 6. 5 | 8. 7 | 2 | 3. 2. 5. 4 | 7. 6. 5. 8 | 3 | 3. 8. 7 | 4 | 6 | | | " | 311-320 | 8 | 3 | 5. 4. 7. 6 | 3. 2. 6. 5 | 7 | 2 | 3. 2. 5. 4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0. 82 5 | 321-330 | 8 | 3 | 6 | 4. 6. 5 | 7 | 2 | 3. 5. 4 | 8 | 4. 3 | 7 | 7 | 3 | | | " | 331-340 | 8 | 3 | 7. 4. 7. 6 | 3. 2. 4. 6. 5 | 7 | 3. 2 | 3. 5. 4 | 8 | 3 | 7 | 6 | 4 |13 | 7 | 1: 0. 54 7 | 341-350 | 8 | 3 | 7. 6 | 5 | 8. 7 | 1. 3. 1. 2 | 3. 5. 4 | 8 | 3 | 7 | 6 | 4 | | | " | 351-360 | 8 | 3 | 7. 6 | 5 | 8. 7 | 2 | 3. 5. 4 | 8 | 3 | 7 | 7 | 3 |13 | 7 | 1: 0. 54 8 | 361-370 | 7. 8 | 3 | 4. 7. 6 | 3. 5 | 8. 7 | 2 | 3. 4 | 9. 8 | 3 | 7 | 4 | 6 | | | | 371-380 | 8 | 3 | 7. 6 | 3. 4. 4. 3. 5 | 8. 7 | 3. 2 | 3. 4 | 8 | 3 | 7 | 5 | 5 | 9 |11 | 1: 1. 22 9 | 381-390 | 8 | 3 | 6 | 4. 2. 1. 5 | 7 | 2 | 3. 4 | 8 | 3 | 8. 7 | 7 | 3 | | | " | 391-400 | 8 | 3 | 6 | 5 | 7 | 2 | 3. 4 | 8 | 3 | 7 | 9 | 1 |16 | 4 | 1: 0. 25 10 | 401-410 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0. 00--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | 1. 2. 3. 4. 5 | | | | | | 1. 2. 3. 4 | 2. 3. 4. 5 | | | | | | | 5. 6. 7. 8 | 2. 3. 4. 5. 6 | 6. 7. 8. 9 | 5. 6. 7 | 1. 2. 3. 4 | 4. 5. 6 | 2. 3. 4. 5 | 1. 2. 3 | 5. 6. 7 | 6. 7. 8. 9 | | | | | | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- 11 | 1-10 | 6. 7 | 3. 5 | 8 | 6 | 3 | 5 | 3. 4 | 3. 2 | 7. 7. 2. 6 | 8 | 5 | 5 | 5 | 5 | 1: 1. 00 12 | 11-20 | 7 | 3. 6. 6. 2. 5 | 8 | 6 | 3 | 4. 5 | 4 | 2 | 7. 6 | 8 | 7 | 3 | 7 | 3 | 1: 0. 43========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

[Footnote *: Aided by experimenter. ]

Examination of table 5 indicates that some of the settings proved veryeasy for Sobke; others, extremely difficult. Consequently, the number ofmethods which were tried and rejected for a given setting varies fromtwo to five. Setting 2 proved a fairly simple one, and after theinhibition of the tendency to choose the first box at the left, the onlydefinite tendency to appear was that of choosing the first box at theright, and then the one next to it. After one hundred and thirty trials, this method suddenly gave place to direct choice of the right box, andduring the following twenty-eight series, no error occurred for thissetting. Setting 4, on the contrary, proved extremely difficult, and avariety of methods is more or less definitely indicated by the records. 

It is needless to lengthen the description by analyzing the data foreach setting, since the reader by carefully scanning the columns of datain table 5 may observe for himself the various tendencies and theirmutual relations. 

Sobke's curve of learning (figure 19) in problem 2, is extremelyirregular, as was that of Skirrl. Similar irregularities appear in thedaily ratios of right to wrong first choices presented in the lastcolumn of table 5. Most of these irregularities were due, I havediscovered, to unfavorable external conditions. Thus, dark rainy daysand disturbing noises outside the laboratory were obviously conditionsof poor work. 

On the day following the final and correct series for problem 2, acontrol series was given. In this Sobke seemed greatly surprised by thenew situations which presented themselves. Repeatedly he exhibitedimpulses to enter the box which would have been the correct one in theregular series of settings. He frequently inhibited such impulses andchose correctly, but at other times he reacted quickly and mademistakes. It was evident from his behavior that he was not guided byanything like a definite idea of the relation of the right box to theother members of the group. 

In a second control series given on the following day, June 12, confusion appeared, but less markedly. For the first setting, a correctchoice was made with deliberation. For the second setting, box 3 wasimmediately chosen, as should have been the case in the regular seriesof settings. Sobke seemed confused when he emerged from this box and haddifficulty in locating the right one. Then followed direct correctchoices for settings 3, 4, and 5. For setting 6, there is recorded adeliberately made wrong choice, and so on throughout the series, thechoices being characterized by deliberateness and definite search forthe right box. Uncertainty was plainly indicated, and in this thebehavior of the animal differed markedly from that in the concludingseries of the regular experiment. 

It seems safe to conclude from the results of these control series thatSobke has no free idea of the relation of secondness from the right andis chiefly dependent upon memory of the particular settings for cueswhich lead to correct choice. 

_Problem 3. Alternately First at Left and First at Right_

For four successive days after the last control series in connectionwith problem 2, Sobke was merely fed in the apparatus according toprevious description (p. 43). He exhibited a wonderfully keen appetiteand was well fed during this interval between problems. 

The method of experimentation chosen for problem 3 in the light ofprevious experience was that of confining the monkey for a short time, ten to fifteen seconds, in the wrong box, in each of the first tenmistakes for a given trial, and of then aiding him to find the right boxby the slight and momentary raising of the exit door. Aid provednecessary in a few of the trials during the first four days. Then heworked independently. As work progressed it was found possible and alsodesirable to increase the period of confinement, and in the end, sixtyseconds proved satisfactory. It was also thought desirable to increasethe number of trials per day from a single series during the early daysto two or even three series from June 29 on. Often three series could begiven in succession without difficulty. During the early trials on thisproblem Sobke worked remarkably well, but later his willingnessdiminished, evidently because of his failure readily to solve theproblem, and it became extremely difficult to coax him into theapparatus. On days when he entered only reluctantly and as it seemedagainst his will, he was likely to be nervous, erratic, and often slowin making his choices, but above all he tended to waste time by notreturning to the starting point, preferring rather to loiter in thealleyways or run back and forth. 

TABLE 6

Results for Sobke, _P. Rhesus_, in Problem 3

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | | | | | | | 3. 4. 5. 6 | 3. 4. 5. 6 | R | W | R | W | of | trials | 5. 6. 7 | 5. 6. 7 | 1. 2. 3. 4. 5. 6 | 1. 2. 3. 4. 5. 6 | 4. 5. 6. 7. 8 | 4. 5. 6. 7. 8 | 2. 3. 4. 5 | 2. 3. 4. 5 | 7. 8. 9 | 7. 8. 9 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | June | | | | | {3. 1. 2. 1 | {7. 8. 7. 8 | | | | {9. 8. 7. 9 | | | | | | 17 | 1--10 | {6. 6. 7. 6 | 5. 7 | {4. 4. 3. 5. 4 | {4. 4. 2. 1 | {8. 8. 7. 8 | 8 | 2 | 3. 2. 5 | {8. 7. 6. 9 | 3. 8. 9 | 2 | 8 | 2 | 8 | 1:4. 00 | | {6. 5 | | {5. 4. 2. 1 | {5. 4. 6* | {7. 7. 4* | | | | {8. 7. 3* | | | | | | | | | | | | | | | | | | | | | | | | | | {3. 4. 2. 5 | | {8. 7. 7. 5 | | | | | | | | | | 18 | 11--20 | 6. 6. 6. 5 | 5. 7 | {4. 5. 6. 4 | 3. 1. 4. 3. 6 | {8. 8. 7. 8 | 8 | 3. 2 | (3. 4. 2. 4 | 9. 8. 8. 7. 3 | 8. 6. 9 | 1 | 9 | 1 | 9 | 1:9. 00 | | | | {2. 3. 1* | | {7. 8. 4* | | | {4. 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | {3. 6. 5. 4 | | {8. 8. 7. 7 | | | | | | | | | | 19 | 21--30 | 6. 5 | 7 | {2. 5. 2. 6 | 3. 6 | {7. 8. 8. 8 | 8 | 4. 3. 2 | {3. 2. 4. 2 | {9. 8. 7. 9. 7 | 9 | 3 | 7 | 3 | 7 | 1:2. 33 | | | | {3. 5. 1* | | {8. 4 | | | {2. 5 | {6. 5. 4. 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | (8. 8. 8. 8 | | | | {9. 9. 8. 9 | | | | | | 21 | 31--40 | 6. 5 | 5. 6. 5. 7 | {3. 5. 4. 6 | 2. 5. 3. 6 | {7. 8. 3. 8 | 8 | 4. 2 | 2. 5 | {9. 5. 9. 9 | 9 | 2 | 8 | 2 | 8 | 1:4. 00 | | | | {4. 3. 5. 1 | | {8. 7. 4* | | | | {9. 9. 3* | | | | | | | | | | | | | | | | | | | | | | 22 | 41--50 | 7. 6. 5 | 6. 5. 5. 7 | 1 | 2. 1. 3. 6 | {8. 8. 8. 8 | 8 | 2 | 2. 3. 2. 2. 5 | {9. 8. 9. 8. 7 | 9 | 4 | 6 | 4 | 6 | 1:1. 50 | | | | | | {7. 8. 4 | | | | {6. 5. 9. 3 | | | | | | | | | | | | | | | | | | | | | | 23 | 51--60 | 5 | 6. 5. 7 | 1 | {1. 2. 1. 1 | 8. 5. 4 | 8 | 5. 4. 2 | 2. 4. 2. 5 | {9. 8. 4. 9 | 9 | 4 | 6 | 4 | 6 | 1:1. 50 | | | | | {3. 2. 6 | | | | | {7. 3 | | | | | | | | | | | | | | | | | | | | | | 24 | 61--70 | 7. 6. 5 | 7 | 2. 3. 1 | 2. 1. 5. 4. 2. 6 | 8. 7. 8. 4 | 8 | 4. 5. 4. 3. 2 | 2. 2. 4. 5 | 9. 7. 6. 8. 3 | 9 | 3 | 7 | 3 | 7 | 1:2. 33 25 | 71--80 | 6. 5 | 5. 7 | 3. 1 | 6 | 8. 5. 4 | 8 | 2 | 3. 2. 5 | 9. 8. 7. 3 | 3. 9 | 3 | 7 | 3 | 7 | 1:2. 33 | | | | | | | | | | | | | | | | 26 | 81--90 | 7. 7. 6. 5 | 6. 5. 7 | 3. 1 | {1. 4. 1. 1 | 8. 4 | 8 | 5. 4. 2 | 2. 5 | 9. 8. 9. 6. 3 | 9 | 2 | 8 | 2 | 8 | 1:4. 00 | | | | | {5. 1. 6 | | | | | | | | | | | | | | | | | | | | | | | | | | | 28 | 91--100 | 7. 6. 5 | 7 | 1 | 1. 2. 4. 6 | 8. 4 | 8 | 2 | 3. 2. 2. 2. 5 | 9. 8. 8. 7. 9. 3 | 9 | 5 | 5 | 5 | 5 | 1:1. 00 | | | | | | | | | | | | | | | | 29 | 101--110 | 7. 6. 5 | 5. 7 | 1 | {1. 1. 5. 3 | 8. 4 | 8 | 2 | 4. 2. 5 | {9. 9. 8. 9. 4 | 9 | 4 | 6 | | | | | | | | {2. 1. 6 | | | | | {9. 7. 6. 3 | | | | | | | | | | | | | | | | | | | | | | " | 111--120 | 6. 5 | 6. 5. 7 | 1 | 2. 1. 1. 3. 6 | 8. 5. 4 | 8 | 2 | 3. 2. 5 | 9. 8. 7. 6. 4. 3 | 9 | 4 | 6 | 8 |12 | 1:1. 50 30 | 121--130 | 5 | 6. 5. 6. 5. 5. 7 | 1 | 3. 1. 6 | 8. 7. 6. 8. 5. 4 | 8 | 2 | 4. 2. 4. 2. 5 | 9. 3 | 9 | 5 | 5 | | | " | 131--140 | 5 | 7 | 1 | 2. 3. 6 | 8. 5. 6. 4 | 8 | 2 | 5 | 9. 8. 3 | 3. 9 | 6 | 4 |11 | 9 | 1:0. 82 July | | | | | | | | | | | | | | | | 1 | 141--150 | 5 | 7 | 1 | 1. 6 | 8. 7. 4 | 8 | 2 | 3. 2. 5 | 9. 8. 6. 9. 3 | 9 | 6 | 4 | | | " | 151--160 | 5 | 7 | 1 | 2. 5. 3. 6 | 8. 4 | 8 | 2 | 2. 5 | 9. 3 | 8. 8. 7. 5. 4. 9 | 5 | 5 |11 | 9 | 1:0. 82 2 | 161--170 | 6. 5 | 7 | 1 | 2. 6 | 8. 4 | 8 | 2 | 3. 5 | 9. 3 | 9 | 5 | 5 | 5 | 5 | 1:1. 00 3 | 171--180 | 6. 5 | 7 | 1 | 1. 5. 6 | 8. 4 | 8 | 2 | 3. 5 | 9. 3 | 9 | 5 | 5 | | | " | 181--190 | 5 | 7 | 1 | 4. 6 | 8. 6. 4 | 8 | 2 | 5 | 9. 8. 4. 8. 5. 3 | 9 | 7 | 3 |12 | 8 | 1:0. 67 5 | 191--200 | 6. 5 | 5. 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 9. 5. 3 | 9 | 6 | 4 | | | " | 201--210 | 5 | 7 | 6. 1 | 2. 6 | 8. 6. 4 | 8 | 5. 3. 5. 4. 3. 2 | 4. 3. 5 | 9. 7. 3 | 9 | 4 | 6 |10 |10 | 1:1. 00 | | | | | | | | | | | | | | | | 6 | 211--220 | 5 | 5. 7 | 1 | 2. 6 | 8. 6. 4 | 8 | 2 | 4. 3. 5 | 9. 3 | {5. 4. 8. 3 | 4 | 6 | | | | | | | | | | | | | | {8. 5. 4. 9 | | | | | | | | | | | | | | | | | | | | | " | 221--230 | 5 | 7 | 1 | 5. 3. 6 | 8. 6. 8. 4 | 8 | 4. 2 | 3. 2. 5 | 9. 3 | 9 | 5 | 5 | 9 |11 | 1:1. 22 7 | 231--240 | 5 | 7 | 1 | 2. 6 | 8. 4 | 7. 4. 8 | 2 | 4. 3. 5 | 8. 3 | 9 | 5 | 5 | | | " | 241--250 | 5 | 7 | 2. 6. 3. 5. 1 | 6 | 8. 4 | 8 | 2 | 5 | 9. 3 | 9 | 7 | 3 | | | | | | | | | | | | | | | | | | | | | | | {2. 6. 2. 6. 4 | | | | | | | | | | | | " | 251--260 | 5 | 7 | {6. 3. 2. 6 | 6 | 8. 4 | 8 | 2 | 5 | 9. 5. 3 | 9 | 7 | 3 |19 |11 | 1:0. 58 | | | | {5. 4. 3. 1 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 8 | 261--270 | 7. 5 | 7 | 1 | 6 | 8. 4 | 8 | 5. 2 | 5 | 8. 3 | 8. 5. 4. 9 | 5 | 5 | | | " | 271--280 | 5 | 7 | 2. 6. 4. 6. 1 | 6 | 8. 5. 8. 4 | 7. 4. 8 | 5. 5. 3. 5. 2 | 5 | 9. 3 | 9 | 5 | 5 |10 |10 | 1:1. 00 | | | | | | | | | | | | | | | | 9 | 281--290 | 5 | 5. 7 | 1 | 6 | 8. 4 | 8 | 2 | 2. 5 | 8. 3 | {7. 3. 8. 6. 8 | 5 | 5 | | | | | | | | | | | | | | {4. 7. 3. 9 | | | | | | | | | | | | | | | | | | | | | " | 291--300 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 9. 3 | 9 | 8 | 2 | | | " | 301--310 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 5. 2 | 5 | 9. 5. 3 | 9 | 7 | 3 |20 |10 | 1:0. 50 10 | 311--320 | 5 | 7 | 1 | 6 | 8. 4 | 7. 4. 8 | 2 | 5 | 9. 3 | 9 | 7 | 3 | | | " | 321--330 | 5 | 7 | 1 | 5. 2. 6 | 8. 7. 4 | 8 | 2 | 5 | 9. 3 | 9 | 7 | 3 |14 | 6 | 1:0. 43 12 | 331--340 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 8. 3 | 9 | 8 | 2 | | | " | 341--350 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 5. 2 | 5 | 9. 3 | 9 | 7 | 3 |15 | 5 | 1:0. 33 13 | 351--360 | 5 | 5. 7 | 1 | 6 | 8. 4 | 8 | 5. 2 | 5 | 3 | 9 | 7 | 3 | | | " | 361--370 | 5 | 7 | 6. 1 | 6 | 4 | 8 | 5. 2 | 3. 2. 5 | 9. 3 | 9 | 6 | 4 |13 | 7 | 1:0. 54 14 | 371--380 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 3 | 7. 4. 3. 9 | 8 | 2 | | | " | 381--390 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 9. 3 | 4. 7. 3. 9 | 7 | 3 |15 | 5 | 1:0. 33 15 | 391--400 | 5 | 5. 5. 7 | 1 | 3. 6 | 8. 4 | 8 | 3. 2 | 5 | 8. 3 | 9 | 5 | 5 | | | " | 401--410 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 7. 3 | 6. 5. 3. 9 | 7 | 3 |12 | 8 | 1:0. 67 16 | 411--420 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | | | " | 421--430 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 4. 7. 4. 9 | 9 | 1 | | | " | 431--440 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 3 | 5. 7. 3. 9 | 8 | 2 |26 | 4 | 1:0. 15 17 | 441--450 | 5 | 7 | 1 | 6 | 4 | 4. 8 | 2 | 5 | 4. 3 | 3. 5. 9 | 7 | 3 | | | " | 451--460 | 5 | 7 | 1 | 3. 6 | 4 | 5. 4. 8 | 2 | 5 | 9. 3 | 9 | 7 | 3 | | | " | 461--470 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 9 |10 | 0 |24 | 6 | 1:0. 25 19 | 471--480 | 5 | 7 | 1 | 6 | 8. 4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | 9 | 1 | 1:0. 11--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | | | 5. 6 | 5. 6 | 4. 5. 6. 7. 8. 9 | 4. 5. 6. 7. 8. 9 | 1. 2. 3. 4. 5 | 1. 2. 3. 4. 5 | 2. 3. 4. 5. 6. 7 | 2. 3. 4. 5. 6. 7 | 3. 4. 5. 6. 7. 8 | 3. 4. 5. 6. 7. 8 | | | | | | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- 19 | 1--10 | 5 | 6 | 4 | 9 | 1 | 5 | 3. 7. 2 | 7 | 3 | 8 | 9 | 1 | 9 | 1 | 1:0. 11========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

[Footnote *: Aided by experimenter. ]

The data of table 6 indicate for this problem only three pronouncedreactive tendencies: (a) As the initial tendency, the choice of thesecond box from the right end. This proved surprisingly weak, in view ofthe animal's long training on problem 2, and it disappeared quickly. (b)Choice of the end boxes, and (c) direct choice of the right box. 

For this, as for the other problems, extreme differences in method andin time and degree of success appear for the different settings. Thus, while settings 1, 2, 3, 6, 7, and 10 proved to be easy, settings 4, 5, 8, and 9 were evidently more difficult. 

[Illustration: FIGURE 20. --Error curve of learning for the solution ofproblem 3 (alternately the first box at the left end and the first atthe right end) by Sobke. ]

From the first this problem promised to be much easier for Sobke thanproblem 2, and although the actual number of trials necessary for thesolution is greater by sixty for problem 3 than for problem 2, comparison of the data of the tables justifies the statement that thethird problem was both easier and more nearly adequately solved than thesecond. This is not surprising when the nature of the two problems isconsidered, for whereas problem 2 requires choice by perception of therelationship of secondness from the right end of the group, problem 3requires, instead, the choice of the end member of the group each time, with the additional variation of alternation of ends. Now as it happens, the end member is easily selected by the monkey, and it appears furtherthat alternation was relatively easy for Sobke to acquire. Consequently, the combination of end and alternation proved easier than the choice ofthe second from the right end of the group. 

The above statements are supported by comparison of the curves oflearning. The curve for problem 2, figure 19, is extremely irregular;that for problem 3, figure 20, much more regular. Similarly, the dailyratios of right to wrong choices as exhibited in tables 5 and 6 indicatesmaller variations for the third problem than for the second. 

Sobke made ten correct first choices in the third series for July 17, but he was working very uncertainly and it seemed rather a matter ofgood luck than good management that he succeeded in presenting thisperfect series: For this reason and also because it did not seemfeasible to have Sunday intervene between the final and perfect regularseries and the control series, an additional regular series was given onJuly 19, in which, as the table indicates, a single mistake occurred, intrial 5. The monkey was working perfectly. The series of trials requiredonly ten minutes, and it was evident that carelessness and eagerness toobtain food were chiefly responsible for the mistake. 

The control series given on July 19 immediately after the series justdescribed resulted similarly in one failure and nine successes. Thechoices were made easily and with certainty, and the only mistake, thatof setting 7, was apparently due to carelessness. 

This excellent showing for the control series wholly justifies thecomparison of problems 2 and 3 as to difficultness, made above. Whereasin both problems 1 and 2 the control trials caused confusion, in thecase of problem 3, they did not essentially alter the behavior of theanimal. The fact seems to be that for this problem the particularsetting is of relatively little importance; while turning alternately tothe extreme left and the extreme right is of prime importance. ThatSobke had the idea of alternation or of the end box, there seems no morereason for insisting than that he had the idea of secondness from theright end in problem 2. It is possible, even probable, that these ideasexisted rather vaguely in his consciousness, but there is obviously nonecessity for insisting that the solution of the problems depended uponthem. 

_Problem 4. Middle_

As the available time for the continuation of the experiment waslimited, it was decided to proceed with work on problem 4 immediatelyupon the completion of problem 3, and on July 20, the problem of themiddle door was presented to Sobke. Since it was anticipated that thissudden change would confuse and discourage him greatly, the only form ofpunishment administered was the momentary lowering of the entrance doorof the wrong box. As in the previous problem, he was aided after tensuccessive wrong choices. As might have been anticipated, hepersistently entered the end boxes of the groups, and this in someinstances probably would have been kept up for many minutes had not theexperimenter lured him into the right box by slightly raising the exitdoor. In the first series, he had to be aided in five of the ten trials. The total time for the series was forty-five minutes, the total numberof choices, eighty-eight. In the second series, he was aided in four ofthe trials. The total time required was seventy-two minutes, and thetotal number of choices was seventy-six. 

Throughout the first series, Sobke worked hard, but with evidentlyincreasing dissatisfaction. He clung persistently to his acquiredtendency to choose the end boxes, and after each trial he returned lesswillingly to the starting point. Up to this time his attitude toward theexperimenter had been perfectly friendly, if not wholly trustful. Butwhen on July 21 he was brought into the apparatus for the second series, he exhibited a wholly new form of behavior, for instead of attendingdiligently to the open doors and devoting his energies to trying to findthe right box, he instead, after gazing at them for a few seconds, turned toward the experimenter and jumped for him savagely, throwinghimself against the wire netting with great force. This was repeated anumber of times during the first two or three trials, and it occurredless frequently later in the series. Since nothing unusual had happenedoutside of the experiment room, the suggested explanation of this suddenchange in attitude and behavior is that the monkey resented and blamedon the experimenter the difficulty which he was having in obtainingfood. 

From this time on until the end of my work, Sobke was always savage andboth in and out of the apparatus he was constantly on the watch for anopportunity to spring upon me. Previously, it had been possible for meto coax him into the apparatus by offering him food and to return him tohis cage by walking after him. But on and after the twenty-first ofJuly, it was impossible for me to approach him without extreme risk ofbeing bitten. 

Doctor Hamilton when told of this behavior, reported that several timesmonkeys have shown resentment toward him when they were having troublein the experiment. I therefore feel fairly confident that I have notmisinterpreted Sobke's behavior. When on July 22 I gave Sobke anopportunity to enter the apparatus, he refused, and it was impossible tolure him in with food. Two hours later, having waited meantime for hisbreakfast, he entered readily and worked steadily and persistentlythrough his third series of trials, but in no one of these trials did hechoose correctly. Neither on this day nor the following did he exhibitresentment while at work. He apparently had regained his affective poiseand was able to attend as formerly to the task of locating his rewards. 

During these first three series, although the ratio of right to wrongchoices stood 0 to 10, there occurred a marked reduction in the numberof trials in which aid was necessary as well as in the total number ofchoices, and on July 23 correct reactions began to appear. Improvementduring the next hundred trials was steady and fairly rapid, and on July31, a record of seven right to three wrong trials was obtained. This wassurprising to the experimenter, as well as gratifying, since he waseager to have the animal complete this problem before work should haveto be discontinued. 

Everything went smoothly until August 2, when my assistant, who had beenleft in charge of the experimental work for a week, attempted toincrease the number of trials per day to two series. Sobke apparentlywas not quite ready for this increase in the amount of his day's laborand refused to work at the end of the first series. In this series hedid less well than on the previous day. The following day, August 3, unfortunately and contrary to the wishes of the experimenter, thelaboratory was painted and there was necessarily considerabledisturbance because of the presence of the workmen, and in addition, thepervasive odor of fresh paint. Sobke chose still less successfully onthis date, and on August 4, he refused to work after the eighth trial. It is true that during these bad days the total number of choicessteadily diminished while the successes, also, diminished, or at best, failed to increase. When on August 9, I returned to the laboratory totake charge, I found that Sobke was no longer trying to solve theproblem as when I had gone away. His attitude had changed in that he hadbecome indifferent, careless, and obviously discouraged with his task. 

TABLE 7

Results for Sobke, _P. Rhesus_, in Problem 4

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | 1. 2. 3. 4 | | | 1. 2. 3. 4. 5 | | | 3. 4. 5. 6 | | R | W | R | W | of | trials | 2. 3. 4 | 5. 6. 7. 8. 9 | 5. 6. 7 | 7. 8. 9 | 4. 5. 6. 7. 8 | 6. 7. 8. 9 | 1. 2. 3 | 2. 3. 4. 5. 6 | 7. 8. 9 | 6. 7. 8 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | July | | | {5. 9. 5. 5 | {1. 7. 1. 3 | {9. 7. 9. 7 | | {1. 9. 3. 1 | | {6. 3. 2. 6 | | | | | | | 20 | 1- 10 | 2. 4. 2. 4. 3 | {5. 9. 5. 6 | {1. 7. 1. 7 | {7. 9. 7. 9 | {8. 4. 8. 4 | {9. 2. 9. 3 | 3. 1. 3. 2 | {3. 6. 3. 2 | {9. 3. 4. 3 | {8. 6. 6. 8. 6 | 0 |10 | 0 |10 | 0:10. 00 | | | {5. 8. 7* | {1. 7. 4* | {7. 7. 8 | {4. 6 | {9. 1. 5* | | {6. 3. 4* | {3. 9. 3. 6 | {8. 6. 8. 6. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | {7. 9. 7. 7 | {4. 8. 5. 5 | {1. 4. 3. 2 | | | {3. 9. 3. 8 | | | | | | 21 | 11- 20 | 2. 3 | {5. 6. 5. 5 | {1. 2. 7. 1 | {7. 9. 7. 7 | {8. 4. 8. 4 | {8. 9. 1. 9 | 3. 1. 2 | {6. 2. 3. 2. 6 | {4. 3. 3. 5 | 6. 7 | 0 |10 | 0 |10 | 0:10. 00 | | | {9. 5. 5. 7 | {7. 3. 7. 4 | {9. 7. 8* | {5. 4. 6* | {1. 9. 5* | | {3. 5. 2. 4 | {3. 4. 6* | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {3. 7. 4. 8 | | | | | | 22 | 21- 30 | 2. 3 | 5. 6. 5. 6. 7 | 1. 7. 4 | {7. 9. 7 | 4. 7. 4. 6 | {1. 4. 6. 3 | 3. 1. 2 | 5. 2. 6. 4 | {4. 3. 5. 8 | 6. 6. 7 | 0 |10 | 0 |10 | 0:10. 00 | | | | | {7. 7. 8 | | {2. 7. 5 | | | {3. 7. 6* | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {5. 4. 7. 4 | | | | | | 23 | 31- 40 | 2. 4. 3 | 5. 6. 8. 7 | 1. 7. 4 | {7. 7. 7. 7 | 4. 7. 6 | 2. 7. 5 | 3. 1. 2 | 6. 4 | {7. 5. 4. 3 | 7 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | {7. 7. 8 | | | | | {7. 3. 6 | | | | | | | | | | | | | | | | | | | | | | 24 | 41- 50 | 3 | 5. 6. 7 | 1. 6. 4 | 7. 7. 7. 8 | 4. 7. 6 | {2. 7. 6. 4 | 3. 2 | 6. 5. 4 | 5. 3. 8. 6. 6 | 7 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | | | {2. 7. 3. 8 | | | | | | | | | | | | | | | | {9. 6. 5* | | | | | | | | | | | | | | | | | | | | | | | | | 26 | 51- 60 | 4. 3 | 6. 5. 7 | 2. 7. 4 | 7. 8 | 6 | {6. 4. 2. 7 | 3. 2 | {6. 5. 3. 5. 2 | 7. 6 | 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | | | {4. 8. 6. 5 | | {6. 5. 6. 4 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {4. 7. 3. 7 | | | | | | | | | 27 | 61- 70 | 3 | 6. 5. 7 | 2. 5. 4 | 7. 7. 8 | 5. 7. 6 | {4. 6. 1. 4 | 2 | 6. 5. 4 | 5. 7. 6 | 6. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | | | {7. 3. 5 | | | | | | | | | | | | | | | | | | | | | | | | | 28 | 71- 80 | 3 | 7 | 6. 5. 4 | 7. 8 | 5. 4. 7. 6 | 2. 7. 6. 5 | 2 | 5. 5. 4 | 7. 6 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | | | | | | | | 29 | 81- 90 | 3 | 6. 5. 7 | 2. 4 | 7. 7. 8 | 5. 4. 6 | {2. 7. 7. 6 | 2 | 4 | 5. 4. 7. 6 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | {2. 7. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | 30 | 91-100 | 3 | 7 | 2. 6. 5. 4 | 7. 8 | 6 | 5 | 2 | 5. 4 | 5. 4. 6 | 7 | 6 | 4 | 6 | 4 | 1: 0. 67 31 | 101-110 | 3 | 7 | 2. 4 | 7. 8 | 6 | 5 | 2 | 4 | 7. 6 | 7 | 7 | 3 | 7 | 3 | 1: 0. 43 August | | | | | | | | | | | | | | | | 2 | 111-120 | 3 | 7 | 6. 5. 7. 6. 4 | 7. 8 | 6 | 4. 2. 7. 6. 5 | 2 | 6. 5. 4 | 7. 6 | 7 | 5 | 5 | 5 | 5 | 1: 1. 00 3 | 121-130 | 3 | 6. 5. 7 | 7. 6. 5. 4 | 7. 8 | 7. 6 | 5 | 2 | 6. 5. 4 | 7. 6 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | | | | | | | | 4 | 131-140 | 3 | 7 | 6. 5. 7. 6. 4 | 7. 8 | 6 | {2. 7. 6. 4 | 2 | 6. 4 | 3. 5. 4. 6 | 7 | 5 | 5 | 5 | 5 | 1: 1. 00 | | | | | | | {8. 7. 6. 5 | | | | | | | | | | | {2. 4. 4. 4 | | | | | | | | | | | | | | 5 | 141-150 | {2. 4. 4. 2 | 6. 5. 7 | {2. 7. 6. 7 | 8 | 7. 6 | {2. 8. 7. 6 | 3. 2 | 6. 4 | 7. 6 | 8. 7 | 1 | 9 | 1 | 9 | 1: 9. 00 | | {4. 3* | | {5. 4 | | | {8. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | 6 | 151-160 | 2. 4. 4. 3 | 7 | 2. 6. 5. 4 | 7. 8 | 7. 6 | 7. 6. 5 | 2 | 6. 4 | 6 | 7 | 4 | 6 | | | | | | | | | | | | | | | | | | | | | {4. 4. 2. 4 | | | | | | | | | | | | | | " | 161-170 | {4. 2. 4. 2 | 7 | 6. 5. 4 | 7. 8 | 7. 6 | 7. 6. 5 | 3. 2 | 5. 4 | 7. 6 | 7 | 2 | 8 | 6 |14 | 1: 2. 33 | | {4. 4. 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 7 | 171-180 | 4. 3 | 7 | 6. 5. 4 | 8 | 7. 6 | 5 | 2 | 6. 5. 4 | 7. 6 | 7 | 5 | 5 | | | | | | | | | | | | | | | | | | | " | 181-190 | {4. 2. 4. 4 | 7 | 7. 6. 5. 4 | 7. 8 | 6 | 6. 5 | 2 | 6. 5. 4 | 7. 6 | 7 | 4 | 6 | 9 |11 | 1: 1. 22 | | {2. 4. 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 9 | 191-200 | 3 | 7 | 5. 4 | 8 | 8. 7. 6 | 6. 5 | 2 | 6. 5. 4 | 7. 6 | 8. 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | | | | | | | | 10 | 201-210 | 3 | 7 | 2. 5. 4 | 7. 8 | 7. 6 | {2. 8. 7. 6 | 2 | 6. 5. 4 | 7. 6 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | {8. 7. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | 11 | 211-220 | 3 | 7 | 6. 5. 4 | 7. 8 | 6 | {7. 6. 4. 3 | 2 | 6. 5. 4 | 7. 6 | 7 | 5 | 5 | 5 | 5 | 1: 1. 00 | | | | | | | {2. 7. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | 12 | 221-230 | 3 | 7 | 2. 4 | 7. 8 | 6 | 7. 6. 5 | 2 | 6. 5. 4 | 8. 7. 6 | 7 | 5 | 5 | 5 | 5 | 1: 1. 00 19 | 231-240 | 3 | 7 | 2. 4 | 7. 8 | 6 | 5 | 2 | 6. 4 | 8. 7. 6 | 7 | 6 | 4 | 6 | 4 | 1: 0. 67 | | | | | | | | | | | | | | | | 20 | 241-250 | 3 | 7 | 5. 4 | 8 | 7. 6 | {2. 4. 1. 2. 7 | 3. 2 | 6. 4 | 7. 6 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | {8. 7. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | 21 | 251-260 | 3 | 7 | 6. 5. 4 | 7. 8 | {7. 4. 5. 4 | {6. 4. 3. 2 | 2 | 6. 5. 4 | 8. 7. 6 | 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | {8. 7. 6 | {7. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | 23 | 261-270 | 3 | 7 | 6. 5. 4 | 7. 8 | 6 | 6. 5 | 2 | 6. 5. 4 | 7. 6 | 7 | 5 | 5 | 5 | 5 | 1: 1. 00 24 | 271-280 | 3 | 7 | 6. 4 | 7. 8 | 7. 6 | 2. 5 | 2 | 4 | 7. 4. 3. 8. 7. 6 | 7 | 5 | 5 | 5 | 5 | 1: 1. 00 25 | 281-290 | 3 | 7 | 2. 5. 4 | 8 | 7. 6 | 5 | 2 | 6. 4 | 7. 6 | 7 | 6 | 4 | 6 | 4 | 1: 0. 67 26 | 291-300 | 3 | 7 | 6. 5. 4 | 8 | 7. 6 | 7. 6. 5 | 2 | 6. 5. 4 | 7. 6 | 7 | 5 | 5 | 5 | 5 | 1: 1. 00 27 | 301-310 | 3 | 7 | 2. 6. 5. 4 | 8 | 7. 6 | 5 | 2 | 6. 5. 4 | 7. 5. 4. 9. 8. 6 | 7 | 6 | 4 | 6 | 4 | 1: 0. 67 28 | 311-320 | 3 | 7 | 2. 5. 4 | 8 | 6 | 9. 8. 7. 5 | 2 | 3. 4 | 8. 6 | 7 | 6 | 4 | 6 | 4 | 1: 0. 67========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

[Footnote *: Aided by experimenter. ]

I immediately set about reinstating the former attitude by lessening thenumber of trials and the punishment, and by increasing the value of thereward, but my best efforts, continuing up to August 28, failed markedlyto improve the condition. The number of correct choices did somewhatincrease, but at no time did the animal attain the degree of successwhich he had achieved as early as July 31 in the eleventh series oftrials. 

During the last two weeks of experimentation, all possible efforts wereput forth to discover the best combination of rewards and punishments. Punishment was varied from 0 to confinement of sixty seconds, and manykinds of food in different amounts were tried as rewards, but in spiteof everything Sobke failed to improve markedly. From time to time, notably on August 12 and 21, he exhibited peculiarly strong resentmenttoward me and repeatedly attempted to attack me. 

The outcome of my experiments with problem 4 is peculiarly interestingin that it indicates the importance of a favorable attitude toward thework and the extreme risk from disturbing or discouraging conditions. Itseems not improbable that had the work progressed without change inexperimenter, or method of procedure, and above all without thedisturbance of the painting, Sobke might have solved problem 4 within afew days. This is by no means certain, however, for in problems 2 and 3the ratio of right to wrong choices instead of increasing steadilyincreased very irregularly. 

The detailed results for this problem are given in table 7. Reactivetendencies which appear are: (a) persistent choice of the end boxesfollowed, subsequently, by (b) the tendency to locate the middle boxdirectly. This proved fairly easy when the number of boxes involved wasonly three as in settings 1, 4, 7, and 10. Setting 4 was most difficultof all, because box 9 was avoided or ignored. When the number of openboxes was as great as five, as in settings 2 and 8, the task wasobviously more difficult, but whereas success in setting 2 appearedearly, in setting 8 it failed to appear during the course ofexperimentation. For the settings 3, 6, and 9, involving either seven ornine open boxes, the direct choice of the middle box was next toimpossible, and Sobke tended to choose, first of all, a particular boxtoward one end of the series, for example, box 2, in setting 3, and box7 in setting 9. To the experimenter, as he watched the animal'sbehavior, it looked as though effort each time were being made to locatethe middle member of the group. This appeared relatively easy for groupsof three boxes, extremely difficult for as many as five boxes, andalmost impossible for seven or nine. 

3. Julius, _Pongo pygmaeus_

_Problem 1. First at the Left End_

The orang utan, Julius, was gentle, docile, and friendly with theexperimenter throughout the period of investigation. He at no timeshowed inclination to bite and could be handled safely. As contrastedwith Skirrl and even with Sobke, he adapted himself to themultiple-choice apparatus very promptly, and only slight effort on thepart of the observer was necessary to prepare him, by preliminarytrials, for the regular experiments. But in order to facilitate work, hewas familiarized with the apparatus by means of regular route trainingand feeding in the several boxes from April 5 to April 9. 

On April 10 the apparatus was painted white as has been statedpreviously, and on the following Monday, April 12, Julius when againintroduced to it gave no indications of fear, uneasiness, or dislike, but worked as formerly, making his round trips quickly and eagerlyentering any box which happened to be open, in order to obtain thereward of food. 

The regular experimentation was undertaken on April 13, and the resultsof the first series of trials with Julius are sharply contrasted withthose obtained with the monkeys in that fewer choices were necessary. Instead of the expected ratio of right to wrong first choices, 1 to 2. 5, the orang utan gave a ratio of 1 to 1. An additional markedly differentresult from that obtained with the monkeys is indicated below in thetotal time required for a series of trials. As examples, the data forthe first, second, fifth, and tenth series are presented. 

TIME FOR SERIES OF TRIALS

 1st series 2nd series 5th series 10th seriesSkirrl 35 min. 20 min. 14 min. 10 min. Sobke 14 " 17 " 10 " 9 " (8th series)Julius 12 " 11 " 14 " 9 "

It is also noteworthy that Julius in the presence of visitors or underother unusual conditions worked steadily and well, whereas the monkeys, and especially Sobke, tended to be distracted and often refused to workat all. 

Almost from the beginning of his work on problem l, Julius began todevelop the tendency to enter immediately the open door nearest thestarting point. In case the group of open doors lay to the right of themiddle of the apparatus, this method naturally yielded success; whereasif the group included doors to the left of the middle, it resulted infailure. Obviously it was a most unsatisfactory method, and although itenabled him to make more right than wrong first choices, it preventedhim from increasing the number of right choices, and as table 1indicates, it maintained the ratio of 1 right to . 67 wrong first choicesfor eight successive days. 

On April 23 a break occurred in which the number of correct choices wasreduced from six to five. Julius worked very rapidly and with almost nohesitation in choosing. My notes record "he seems to miss the pointwholly. It is doubtful whether the punishment is sufficiently severe. "At this time he was being punished by thirty seconds confinement in eachwrong box, the interval having been held fairly steadily from the firstseries of experiments. On April 26 it was increased to sixty seconds, inan effort to break him of the habit of choosing the "nearest" door. Buthe became extremely restless under the longer confinement and tried hisbest to raise the entrance and exit doors. Since there was at this timeno mechanism for locking them when closed, it was difficult for theexperimenter to prevent him from escaping by way of the entrance door orfrom raising the exit door sufficiently to obtain the food. Indeed, thelonger confinement worked so unsatisfactorily that on the following dayI substituted for it the punishment of forcing him to raise the entrancedoor of the wrong box in order to escape for a new choice. He wasrewarded with food in the alleyway H, beside door 15 (figure 17), onlywhen he chose correctly on first attempt. 

This method discouraged him extremely and proved wasteful of time. Consequently, in a second series on the same date return was made to theformer method, and he was rewarded with food whenever he found the rightbox. But on April 28, the two methods were again employed, the first inthe initial series and the second in a final series of trials. Theanimal's persistent attempts to raise the doors gave the experimenter somuch trouble that on April 29 barbed wire was nailed over the windows ofthe entrance doors with the hope that it might prevent him from workingat them. But he quickly learned to place his fingers between the barbsand raise the doors as effectively as ever. 

On April 30 the reward of food was given only when the first choice wasthat of the right box and in that event it was placed in the alleyway Has stated above. 

As it seemed absolutely essential to break the unprofitable habit ofchoosing the nearest door, on May 3 a new series of settings waspresented, in which only the doors to the left of the middle of the rowof nine boxes were used as right doors. That is, in this new series, doors 1 to 4 occur as right doors; 5 to 9 do not. As punishment forwrong choices on this date, Julius was confined in the wrong box fromone to five minutes. It was difficult to keep him in, but by means ofcords which had been attached to the doors, this was successfullyaccomplished. Yet another and slightly different series of settings wasemployed on May 4, and this, proving satisfactory, was continued in useuntil the end of the experiment, with punishment ranging from sixty toone hundred and twenty seconds for each mistake. 

Naturally the modification of settings introduced May 3 greatlyincreased the proportion of wrong first choices. Indeed, as appears intable 8, the ratio of right to wrong immediately changed from 1:0. 67 to1:4. 00. Between May 3 and May 10, no steady and consistent improvementin method or in the number of correct first choices occurred, and on thelast named date, Julius chose correctly only three times in his tentrials. At this time there was, as my notes record, no satisfactoryindication of progress, and the status of the experiment seemedextremely unsatisfactory in as much as in spite of the experimenter'sbest efforts to break up the habit of choosing the nearest door, theorang utan still persisted, to a considerable extent, in the use of thismethod. The only encouraging feature of the results was an evidenttendency to choose somewhat nearer the left end of a group thanpreviously. 

TABLE 8

Results for Orang utan in Problem 1

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | | | | | | | | | R | W | R | W | of | trials | 1. 2. 3 | 8. 9 | 3. 4. 5. 6. 7 | 7. 8. 9 | 2. 3. 4. 5. 6 | 6. 7. 8 | 5. 6. 7 | 4. 5. 6. 7. 8 | 7. 8. 9 | 1. 2. 3 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | April | | | | | | | | | | | | | | | | 13 | 1- 10 | 3. 1 | 8 | 4. 3 | 7 | 4. 2 | 7. 6 | 5 | 4 | 7 | 3. 1 | 5 | 5 | 5 | 5 | 1:1. 00 14 | 11- 20 | 3. 2. 1 | 8 | 4. 3 | 7 | 4. 4. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | 6 | 4 | 1:0. 67 15 | 21- 30 | 3. 2. 1 | 8 | 4. 3 | 7 | 4. 5. 5. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | 6 | 4 | 1:0. 67 16 | 31- 40 | 3. 1 | 8 | 4. 3 | 7 | 4. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 6 | 4 | 6 | 4 | 1:0. 67 17 | 41- 50 | 3. 2. 1 | 8 | 4. 3 | 7 | 4. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | 6 | 4 | 1:0. 67 19 | 51- 60 | 3. 1 | 8 | 4. 3 | 7 | 4. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | 6 | 4 | 1:0. 67 20 | 61- 70 | 2. 1 | 8 | 4. 3 | 7 | 5. 3. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | 6 | 4 | 1:0. 67 21 | 71- 80 | 3. 1 | 8 | 4. 3 | 7 | 5. 4. 3. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 6 | 4 | 6 | 4 | 1:0. 67 22 | 81- 90 | 3. 1 | 8 | 5. 3 | 7 | 6. 3. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 6 | 4 | 6 | 4 | 1:0. 67 23 | 91-100 | 3. 2. 1 | 8 | 5. 3 | 7 | 4. 3. 2 | 6 | 5 | 5. 4 | 7 | 3. 2. 1 | 5 | 5 | 5 | 5 | 1:1. 00 24 | 101-110 | 3. 2. 1 | 8 | 4. 3 | 7 | 4. 3. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | 6 | 4 | 1:0. 67 26 | 111-120 | 3. 1 | 8 | 4. 3 | 7 | 4. 3. 2 | 6 | 5 | 5. 4 | 7 | 3. 1 | 5 | 5 | 5 | 5 | 1:1. 00 27 | 121-130 | 3. 2. 1 | 8 | 4. 3 | 7 | 4. 3. 2 | 6 | 6. 5 | 5. 8. 6. 4 | 7 | 3. 3. 3. 1 | 4 | 6 | | | " | 131-140 | 3. 1 | 8 | 4. 3 | 7 | 4. 3. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 6 | 4 |10 |10 | 1:1. 00 28 | 141-150 | 3. 2. 1 | 8 | 3 | 7 | 5. 4. 2 | 6 | 5 | 4 | 7 | 3. 1 | 7 | 3 | | | " | 151-160 | 3. 1 | 8 | 3 | 7 | 3. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 7 | 3 |14 | 6 | 1:0. 43 29 | 161-170 | 3. 1 | 8 | 4. 3 | 7 | 4. 3. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 6 | 4 | | | " | 171-180 | 3. 2. 1 | 8 | 4. 3 | 7 | 4. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 6 | 4 |12 | 8 | 1:0. 67 | | | | | | | | | | | | | | | | 30 | 181-190 | 3. 1 | 8 | 4. 3 | 7 | {4. 5. 6. 4 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | | | | | | | | | {5. 6. 4. 2 | | | | | | | | | | | | | | | | | | | | | | | | | | " | 191-200 | 3. 1 | 8 | 4. 5. 6. 7. 3 | 7 | 4. 5. 3. 2 | 6 | 5 | 4 | 7 | 3. 2. 1 | 6 | 4 |12 | 8 | 1:0. 67 May | | | | | | | | | | | | | | | | 1 | 201-210 | 3. 1 | 8 | 4. 3 | 7 | 3. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 | | | " | 211-220 | 3. 2. 1 | 8 | 4. 3 | 7 | 4. 2 | 6 | 5 | 4 | 7 | 3. 1 | 6 | 4 |12 | 8 | 1:0. 67--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | 2. 3. 4. 5 | | | | | | | 2. 3. 4. 5 | | | | | | | 1. 2. 3 | 3. 4. 5. 6. 7 | 6. 7. 8 | 1. 2. 3 | 3. 4. 5. 6. 7 | 4. 5. 6. 7. 8. 9 | 2. 3. 4. 5 | 1. 2. 3 | 4. 5. 6. 7. 8. 9 | 6. 7. 8. 9 | | | | |--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- 3 | 221-230 | 3. 1 | 4. 3 | 4. 2 | 3. 1 | 4. 3 | 4 | 4. 3. 2 | 3. 1 | 4 | 4. 3. 2 | 2 | 8 | 2 | 8 | 1:4. 00--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | 2. 3. 4. 5 | 4. 5. 6. 7 | | | | | 2. 3. 4. 5 | | | | | | | | 1. 2. 3 | 3. 4. 5. 6. 7 | 6. 7. 8 | 8. 9 | 2. 3. 4. 5 | 3. 4. 5. 6 | 1. 2. 3 | 4. 5. 6. 7. 8 | 6. 7. 8. 9 | 1. 2. 3 | | | | |--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- 4 | 231-240 | 3. 2. 1 | 4. 3 | 4. 2 | 4 | 4. 3. 2 | 4. 3 | 3. 2. 1 | 4 | 3. 2 | 3. 2. 1 | 2 | 8 | 2 | 8 | 1:4. 00 5 | 241-250 | 2. 1 | 3 | 3. 2 | 4 | 3. 2 | 4. 3 | 3. 2. 1 | 4 | 3. 2 | 3. 2. 1 | 3 | 7 | 3 | 7 | 1:2. 33 6 | 251-260 | 2. 1 | 3 | 2 | 4 | 3. 2 | 3 | 2. 1 | 4 | 3. 2 | 2. 1 | 5 | 5 | 5 | 5 | 1:1. 00 7 | 261-270 | 2. 1 | 3 | 3. 2 | 4 | 3. 2 | 3 | 2. 1 | 4 | 4. 2 | 2. 1 | 4 | 6 | 4 | 6 | 1:1. 50 8 | 271-280 | 2. 1 | 4. 3 | 4. 3. 2 | 4 | 3. 2 | 4. 3 | 3. 1 | 4 | 3. 2 | 2. 1 | 2 | 8 | 2 | 8 | 1:4. 00 10 | 281-290 | 1 | 4. 3 | 4. 2 | 4 | 3. 2 | 4. 3 | 2. 1 | 4 | 3. 2 | 2. 1 | 3 | 7 | 3 | 7 | 1:2. 33 11 | 291-300 | 1 | 3 | 2 | 4 | 2 | 3 | 1 | 4 | 2 | 1 |10 | 0 |10 | 0 | 1:0. 00--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | | | 1. 2. 3 | 8. 9 | 3. 4. 5. 6. 7 | 7. 8. 9 | 2. 3. 4. 5. 6 | 6. 7. 8 | 5. 6. 7 | 4. 5. 6. 7. 8 | 7. 8. 9 | 1. 2. 3 | | | | |--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- 12 | 301-310 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0. 00========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

A series of correct first choices was obtained on May 11, greatly to thesurprise of the experimenter, for no indication had previously appearedof this approaching solution of the problem. It seemed possible, however, that the successes were accidental, and it was anticipated thatin a control series Julius would again make mistakes. But on thefollowing day, May 12, the presentation of the original series of tensettings, which, of course, differed radically from the settings usedfrom May 4 to May 11 was responded to promptly, readily, and without asingle mistake. Julius had solved his problem suddenly and, in allprobability, ideationally. 

Only three reactive tendencies or methods appeared during Julius's workon this problem: (a) choice of the open door nearest to the startingpoint (sometimes the adjacent boxes were entered); (b) a tendency toavoid the "nearest" door and select instead one further toward the leftend of the group; (c) direct choice of the first door on the left. 

The curve of learning plotted from the daily wrong choices and presentedin figure 18, had it been obtained with a human subject, wouldundoubtedly be described as an ideational, and possibly even as arational curve; for its sudden drop from near the maximum to the baseline strongly suggests, if it does not actually prove, insight. 

Never before has a curve of learning like this been obtained from aninfrahuman animal. I feel wholly justified in concluding from theevidences at hand, which have been presented as adequately as ispossible without going into minutely detailed description, that theorang utan solved this simple problem ideationally. As a matter of fact, for the solution he required about four times the number of trials whichSobke required and twice as many as were necessary for Skirrl. Were weto measure the intelligence of these three animals by the number oftrials needed in problem 1, Sobke clearly would rank first, Skirrlsecond, and Julius last of all. But other facts clearly indicate thatJulius is far superior to the monkeys in intelligence. We therefore mustconclude that _where very different methods of learning appear, thenumber of trials is not a safe criterion of intelligence. _ Theimportance of this conclusion for comparative and genetic psychologyneeds no emphasis. 

_Problem 2. Second from the Right End_

Julius was given four days' rest before being presented with problem 2. He was occasionally fed in the apparatus, but regular continuation oftraining was not necessary to keep him in good form. During this restinterval, locks were attached to the doors of the apparatus so that theexperimenter by moving a lever directly in front of him could fasteneither one or both of the doors of a given box by a single movement. OnMay 13 Julius was given opportunity to obtain food from each of theboxes in turn, and trial of the locks was made in order to familiarizehim with the new situation. He very quickly discovered that the doorscould not be raised when closed, and after two days of preliminary work, he practically abandoned his formerly persistent efforts to open them. The locks worked satisfactorily from a mechanical point of view as wellas from that of the adaptation of the animal to the modified situation. 

Problem 2 was regularly presented for the first time on May 17, on whichday a single series was given. The period of punishment adopted wastwenty seconds, and for each successful choice a small piece of bananawas given as a reward. After the first trial in this series, in whichJulius repeatedly entered the first box at the left, that is box 7, there was but slight tendency to reënter the first box at the left ofthe group. Instead, Julius developed the method of moving box by boxtoward the right end of the group. The choices were made promptly, andtheir systematic character enabled the animal to obtain his rewardfairly quickly, in spite of the large number of mistakes. 

In the second series, the orang utan developed the interesting trick ofquickly dodging out of the wrong box before the experimenter could lowerthe door behind him. This he did only after having been punished formany wrong choices to the point of discouragement. The trick was easilybroken up by the sudden lowering of the entrance door as soon as he hadpassed under it. 

There appeared on May 21 an unfavorable physical condition whichmanifested itself, first of all through the eyes which appeared dull andbloodshot. On the following day they were inflamed and the lids nearlyclosed. Julius refused to eat, and experimentation was impossible. UntilJune 2 careful treatment and regulation of diet was necessary. He passedthrough what at the time seemed a rather startling condition, butrapidly regained his usual good health, and on June 3, although somewhatweak and listless, he again worked fairly steadily. 

Since it was now possible to lock the doors and confine the animal forany desired period, on June 5 the interval of punishment was made sixtyseconds, and a liberal quantity of banana, beet, or carrot was offeredas reward. No increase in the number of successful choices appeared, andJulius showed discouragement. Sawdust had been strewn on the floor, andin the intervals between trials as well as during confinement in wrongboxes, he took to playing with the sawdust. He would take it up in onehand and pour it from hand to hand until all had slipped through hisfingers, then he would scrape together another handful and go throughthe same process. Often he became so intent on this form of amusementthat even when the exit door was raised, he would not immediately go toget the food. 

The reactive tendencies which appeared in the work on problem 2 will nowbe presented in order, since I shall have to refer to them repeatedly, and the list will be more useful to the reader at this point than at theconclusion of the presentation of daily results. The following is not anexhaustive list but includes only the most important and conspicuoustendencies or methods together with the dates on which they were mostapparent. 

(a) May 17, choice of first box at left of group or near it, then thenext in order, and so on, until the second from the right was reached. This method with irregularities and certain definite skipping was usedat various times, sometimes over periods of several days, during thecourse of the work. 

(b) June 3, preference for number 3 and number 4 developed immediatelyafter the orang utan's illness and when he was working ratherlistlessly. 

On June 9 and 10, the original tendency (a) reappeared and persisted fora number of series. 

(c) June 14, a tendency to choose the box at or near the right end of agroup, and then the one next to it. In connection with this tendency, which of course required only two choices in any given trial, interestin playing with the sawdust on the floor developed. 

Again on June 21, the animal returned to the use of tendency (a). 

(d) June 29, movement to box at right end of group, hesitation beforeit, and turning through a complete circle so that the second box fromthe right was faced. This, the correct box, was often promptly entered. This method, if persisted in, would obviously have yielded solution ofthe problem. 

(e) July 5, approach to and pretense to enter the box next to the rightend (right one), and then choice of some other box. This _feint_ ispeculiarly interesting, and its origin and persistence are difficult toaccount for. 

(f) In connection with the tendency to pretend that he was going toenter the second box from the right end, Julius developed also thetendency to turn around in front of the box at the right end, startingsometimes to back into it, and then to enter, instead, the box secondfrom the end. 

(g) July, 6 and 7, a fairly definite tendency to take the one next inorder or, instead, to go directly to the right box. 

(h) July 10, direct first choices without approach to other boxesappeared for the first time on this date. 

For this problem, it proved impossible to establish and maintain uniformconditions of experimentation. Instead, because of the failure of theanimal to improve and the tendency to discouragement, both punishmentand reward had to be altered from time to time, and other and moreradical changes were occasionally made in the experimental procedure. Below for the sake of condensed and consecutive presentation, the mostimportant conditions from day to day are arranged in tabular form:

CONDITIONS OF EXPERIMENT FROM DAY To DAY FOR PROBLEM 2

Date Punishment Reward

May 17 ............. 20 sec. Confinement ........ Food in right box for each (Aid after 10 trials) trial

 " 18 to 21 ........ 30 sec. Confinement ........ Food (banana) in right box for each trial

 " 22 to June 2 .... Illness, no experiments

June 3 ............... 15 sec. Confinement ........ Food (banana) in right box for each trial

 " 4 ............... 30 " " ............. Food (banana) in right box for each trial

 " 5-10 ............ 60 " " ............. Beet, carrot and loquat, in addition to banana

 " 11 .............. 10 to 30 sec. Confinement .. Beet, carrot and loquat, in addition to banana

 " 12 to 15 ........ 60 sec. Confinement ........ Beet, carrot and loquat, in addition to banana

 " 16 .............. 60 " " ............. Banana and sweet corn--former preferred

 " 17 (1st series). 60 sec. Confinement ........ Food (banana, as in early series)

 " 17 (2nd series). No confinement in wrong box; Food only for correct first but instead, return to choices starting point by way of alleys

 " 18 to 22 ........ No confinement in wrong box; Food only for correct first but instead, return to choices starting point by way of alleys

 " 22 (2nd series). No punishment; allowed to Food for each trial enter boxes until right one was found " 23 .............. Return to starting point. After five wrong choices of a given box the animal was held for 60 secs. In one of the boxes and was then released by way of the exit door and rewarded when the right one was chosen

 " 23 (2nd series). No punishment .............. Reward for each trial

 " 24 (1st series). Return to starting point. .. Food only for correct first choices

 " 24 (2nd series). No punishment .............. Reward for each trial

 " 25-30 ........... Same as on 24th ............ 

July 1 (1st series). No punishment .............. " " " "

 " 1 (2nd series). Return to starting point ... Reward only for correct first choices " 2-8 ............. Same as on July 1 .......... 

 " 8 (2nd series). No punishment .............. Reward for each trial

 " 8 (3rd series). Return to starting point ... Reward only for correct first choices

 " 9-10 ............ Same as for July 8 (3rd series)

 " 10 (2nd series). Momentary confinement in ..... Reward for each correct choice wrong boxes

 " 12 .............. Return to starting point ..... Reward for correct first choice

 " 12 (2nd series). 30 sec. Confinement .......... Reward for each correct choice

 " 12 (3rd series). 5 " " ............... " " " " "

 " 13 .............. 30 " " ............... " " " " "

 " 14-17 ........... Return to starting point ..... Reward for correct first choices

 " 17 (2nd series). 60 sec. Confinement .......... Reward for each correct choice

 " 19 .............. 30 " " ............... " " " " "

 " 20-26 ........... 10 " " ............... " " " " "

 " 27-30 ........... Right box indicated by slight Reward in each right box raising of exit door momentarily. No punishment

 " 30 (2nd series). Return to starting point ..... Reward for correct first choices

 " 31 .............. " " " " ..... " " " " "

 " 31 (2nd series) to Aug. 10 .... 10 to 60 sec. Confinement .... Reward for each correct choice

Aug. 10 (2nd series). Threatened with whip ......... " " " " "

 " 11 (1st series). " " " ........... " " " " "

 " 11 (2nd series). 10 sec. Confinement .......... " " " " "

 " 12 .............. Threatened with whip ......... " " " " "

 " 12 (2nd series). 10 sec. Confinement .......... " " " " "

 " 19 .............. 10 " " ............... " " " " "

 " 19 (2nd series). Threatened with whip ......... " " " " "

With the above reactive tendencies and modifications of method in mindwe may continue our description of results. On June 9 there developed atendency to increase the magnitude of the original error by choosingnearer the left end of the groups. This is odd, since one wouldnaturally suppose that an animal as intelligent as the orang utan wouldtend to avoid the general region in which success was never obtained andto focus attention on the right, as contrasted with the wrong end ofeach group. _It obviously contradicts the law of the gradual eliminationof use less activities. _ In other words, it is wholly at variance withthe principle of trial and error exhibited by many infrahuman organisms. Julius, although making many mistakes, worked diligently and, for themost part, fairly rapidly. The day's work proved most important becauseof the change in method and also because of the appearance ofhesitation, the rejection of certain boxes, and the definite choice ofothers. My notes record "this is a most important day for Julius inproblem 2;" but subsequent results do not clearly justify this prophecy. 

The method of choosing the first box at the left and then of moving downthe line until the right one was reached was so consistently followedthat during a number of days it was possible for me to predict almostevery choice. Indeed, to satisfy my curiosity in this matter during anumber of series I guessed in advance the box which would be chosen. Thepercentages of correct guesses ranged from ninety to one hundred. June10, for example, yielded two series for which the ratio of right towrong first choices was 0 to 10, and in which the method described abovewas used consistently throughout. 

It was inevitable that punishment by confinement and the discouragementresulting therefrom should interfere with the regularity of work andmake it extremely difficult to obtain strictly comparable results fromseries to series and from day to day. The data for this problem, aspresented in table 9, have values quite different from those for themonkeys, chiefly because of the more variable conditions of observation. 

It was occasionally noted that the disintegration of a definite methodand the disappearance of the tendency on which it depended occurredrather suddenly. Frequently it happened that having used an inadequatemethod fairly persistently on a given day, the animal would on thefollowing day exhibit a wholly different method. Even over night a newmethod might develop. In the monkeys, although there was occasionallysomething comparable with this, it was by no means so evident. 

TABLE 9

Results for Orang utan in Problem 2

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | | | | | | 1. 2. 3. 4. 5 | | | R | W | R | W | of | trials | 7. 8. 9 | 1. 2. 3. 4 | 2. 3. 4. 5. 6. 7 | 1. 2. 3. 4. 5. 6 | 4. 5. 6. 7. 8 | 1. 2. 3 | 2. 3. 4. 5 | 6. 7. 8. 9 | 1. 2. 3. 4 | 3. 4. 5. 6. 7. 8 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | May | | {7. 7. 7. 7 | | | | | | | | | | | | | | 17 | 1- 10 | {7. 7. 7. 7 | 1. 1. 3 | 2. 4. 6 | 2. 3. 4. 5 | 4. 5. 7 | 3. 2 | 2. 3. 4 | {2. 3. 4. 5 | 1. 2. 3 | 3. 4. 5. 6. 7 | 0 |10 | 0 |10 | 0:10. 00 | | {7. 7. 8 | | | | | | | {6. 7. 8 | | | | | | | | | | | | | | | | | | {4. 5. 6. 8 | | | | | 18 | 11- 20 | 7. 8 | 1. 3 | 3. 4. 5. 6 | 2. 4. 5 | 4. 5. 6. 7 | 2 | 2. 3. 4 | {2. 3. 4. 5 | 1. 2. 3 | {8. 8. 8. 3 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | | | | | {6. 7. 8 | | {4. 5. 6. 7 | | | | | | | | | | | | | | | | | | | | | | | | | {2. 4. 7. 7. 2 | | | | | | | {5. 3. 4. 5 | | | | | 19 | 21- 30 | 7. 8 | 1. 3 | {5. 7. 7. 2 | 5 | 4. 6. 8. 4. 7 | 1. 2 | 2. 3. 4 | 5. 8 | 3 | {6. 8. 4. 5 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | {3. 2. 4. 6 | | | | | | | {3. 5. 6. 7 | | | | | | | | | | | | | | | | | | | | | 20 | 31- 40 | {7. 9. 7. 7 | 3 | 4. 5. 6 | 4. 5 | 5. 6. 7 | 2 | 4 | 5. 6. 7. 8 | 3 | 5. 6. 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | {9. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 21 | 41- 50 | 7. 8 | 3 | 3. 4. 5. 6 | 4. 5 | 4. 5. 6. 7 | 2 | 3. 4 | 4. 5. 6. 8 | 3 | 4. 5. 6. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 June | | | | | | | | | | | | | | | | 3 | 51- 60 | 7. 8 | 3 | 4. 5. 6 | 3. 4. 5 | 4. 5. 6. 7 | 3. 1. 2 | 3. 4 | {3. 7. 9. 7 | 3 | 4. 5. 6. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | | | | | | | | {9. 7. 6. 8 | | | | | | | | | | | | | | | | | | | | | | | 4 | 61- 70 | 7. 8 | 3 | 4. 5. 6 | 4. 5 | 4. 5. 6. 7 | 3. 3. 1. 2 | 4 | 4. 5. 6. 7. 8 | 3 | 4. 5. 6. 7 | 3 | 7 | 3 | 7 | 1: 2. 33 5 | 71- 80 | 7. 9. 7. 8 | 3 | 3. 4. 5. 6 | 3. 6. 3. 4. 5 | 4. 7 | 3. 1. 2 | 4 | 3. 4. 5. 6. 7. 8 | 3 | 4. 5. 6. 7 | 3 | 7 | | | " | 81- 90 | 7. 8 | 3 | 3. 4. 5. 6 | 3. 4. 5 | 4. 5. 6. 7 | 2 | 3. 4 | 3. 4. 5. 6. 7. 8 | 2. 3 | 4. 5. 6. 7 | 2 | 8 | 5 |15 | 1: 3. 00 | | | | | | | | | | | | | | | | 7 | 91- 100 | 7. 8 | 3 | 4. 5. 6 | 4. 5 | 4. 5. 6. 7 | 1. 2 | 3. 4 | {3. 4. 5. 6 | 2. 3 | {3. 4. 5. 6 | 1 | 9 | 1 | 9 | 1: 9. 00 | | | | | | | | | {7. 8 | | {8. 5. 6. 7 | | | | | | | | | | | | | | | | | | | | | 8 | 101- 110 | 7. 8 | 3 | 4. 5. 6 | 4. 5 | 4. 5. 6. 7 | 2 | 3. 4 | 4. 5. 6. 7. 8 | 3 | 4. 5. 6. 7 | 3 | 7 | | | " | 111- 120 | 7. 8 | 3 | 4. 5. 6 | 3. 4. 5 | 5. 6. 7 | 2 | 5. 5. 2. 3. 4 | 4. 5. 6. 7. 8 | 4. 4. 1. 2. 3 | 4. 5. 6. 7 | 2 | 8 | 5 |15 | 1: 3. 00 | | | | | | | | | | | | | | | | 9 | 121- 130 | 7. 8 | 2. 3 | 4. 5. 6 | 4. 5 | 4. 5. 6. 7 | 2 | 3. 4 | {2. 3. 4. 5 | 1. 2. 3 | 3. 4. 5. 6. 7 | 1 | 9 | | | | | | | | | | | | {6. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 131- 140 | 7. 8 | 1. 2. 3 | 2. 3. 4. 5. 6 | 5 | 4. 5. 6. 7 | 1. 2 | 2. 3. 4 | 6. 7. 8 | 2. 3 | 3. 4. 5. 6. 7 | 1 | 9 | 2 |18 | 1: 9. 00 | | | | | | | | | | | | | | | | 10 | 141- 150 | 7. 8 | 1. 2. 3 | 2. 3. 4. 5. 6 | 1. 2. 3. 4. 5 | 4. 5. 6. 7 | 1. 2 | 2. 3. 4 | {1. 2. 3. 4 | 1. 2. 3 | 3. 4. 5. 6. 7 | 0 |10 | | | | | | | | | | | | {5. 6. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 151- 160 | 7. 8 | 1. 2. 3 | 2. 3. 4. 5. 6 | 1. 2. 3. 4. 5 | 4. 5. 6. 7 | 1. 2 | 2. 3. 4 | {1. 2. 3. 4 | 1. 2. 3 | 3. 4. 5. 6. 7 | 0 |10 | 0 |10 | 0:10. 00 | | | | | | | | | {5. 6. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | 11 | 161- 170 | 8 | {4. 1. 2. 4. 1 | 2. 3. 4. 5. 6 | 5 | 6. 7 | {3. 1. 3. 1 | 5. 2. 3. 4 | 2. 6. 7. 8 | 4. 1. 2. 3 | 8. 5. 6. 7 | 2 | 8 | | | | | | {4. 1. 4. 1. 3 | | | | {3. 1. 2 | | | | | | | | | | | | | | | | | | | | | | | | | " | 171- 180 | 9. 7. 8 | 4. 3 | 5. 6 | 4. 5 | 7 | 3. 1. 2 | 5. 4 | 8 | 4. 2. 3 | 7 | 3 | 7 | 5 |15 | 1: 3. 00 12 | 181- 190 | 7. 9. 7. 9. 8 | 1. 2. 3 | 3. 4. 5. 6 | 6. 4. 5 | 5. 6. 7 | 2 | 5. 3. 4 | 7. 8 | 4. 1. 2. 3 | 4. 5. 6. 7 | 1 | 9 | 1 | 9 | 1: 9. 00 14 | 191- 200 | 9. 8 | 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 6. 7. 8 | 4. 2. 3 | 7 | 2 | 8 | | | " | 201- 210 | 8 | 2. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 1. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | 5 |15 | 1: 3. 00 | | | | | | | | | | | | | | | | 15 | 211- 220 | {7. 9. 7. 9 | 4. 2. 3 | 6 | 5 | 8. 7 | 3. 2 | 5. 4 | 9. 8 | 4. 3 | 7 | 3 | 7 | | | | | {7. 9. 8 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | " | 221- 230 | 9. 8 | 4. 3 | 7. 6 | 6. 5 | 5. 6. 7 | 1. 2 | 2. 3. 4 | 3. 4. 5. 6. 7. 8 | 4. 3 | 7 | 1 | 9 | 4 |16 | 1: 4. 00 16 | 231- 240 | 7. 9. 8 | 3 | 7. 6 | 6. 5 | 8. 7 | 2 | 5. 4 | 5. 6. 7. 8 | 4. 1. 4. 3 | 8. 7 | 2 | 8 | | | " | 241- 250 | 9. 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 6. 7. 8 | 4. 3 | 6. 7 | 1 | 9 | 3 |17 | 1: 5. 67 | | | | | | | | | | | | | | | | 17 | 251- 260 | 9. 8 | 4. 3 | 7. 6 | 6. 5 | {6. 5. 4. 6 | 3. 2 | 5. 4 | 6. 5. 6. 7. 8 | 3 | 5. 6. 7 | 1 | 9 | | | | | | | | | {5. 4. 5. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {6. 6. 6. 5. 6 | | | | | | | | | | | | | | | | {5. 5. 5. 6. 6 | | | | | | | | | | " | 261- 270 | {9. 7. 7. 7 | 4. 4. 4. 4. 3 | 6 | 5 | {6. 6. 6. 6. 6 | {3. 3. 3. 3 | 4 | {4. 5. 4. 5. 4 | 3 | {5. 5. 5. 5 | 4 | 6 | 5 |15 | 1: 3. 00 | | {7. 7. 7. 8 | | | | {6. 5. 4. 5 | {3. 3. 2 | | {5. 6. 7. 8 | | {5. 5. 8. 7 | | | | | | | | | | | {6. 5. 5. 4 | | | | | | | | | | | | | | | | {4. 5. 6. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | 18 | 271- 280 | {7. 7. 7. 7 | 4. 4. 4. 4. 3 | 5. 5. 5. 5. 6 | 5 | {5. 5. 5. 6 | {3. 3. 3. | 4 | {4. 6. 5. 6 | 4. 4. 3 | 5. 6. 4. 7 | 2 | 8 | 2 | 8 | 1: 4. 00 | | {7. 7. 8 | | | | {5. 5. 6 | {3. 3. 2 | | {6. 7. 4. 8 | | | | | | | | | | | | | | | | | | | | | | | | | {7. 7. 7. 9 | | | | | | | | | | | | | | 19 | 281- 290 | {9. 9. 9. 7 | {4. 4. 4 | {5. 7. 7 | 5 | 5. 7 | {3. 3. 3. 3 | 4 | 5. 8 | {4. 4. 4. 4 | {6. 5. 6. 5 | 2 | 8 | | | | | {7. 7. 8 | {4. 4. 3 | {7. 4. 6 | | | {3. 3. 2 | | | {4. 4. 3 | {5. 5. 7 | | | | | | | | | | | | | | | | | | | | | " | 291- 300 | 7. 7. 7. 7. 8 | 4. 4. 4. 4. 3 | 5. 5. 6 | 5 | {5. 6. 6. 5. 6 | 3. 3. 2 | {5. 5. 5. 5 | 5. 6. 8 | 4. 4. 3 | 6. 6. 6. 7 | 1 | 9 | 3 |17 | 1: 5. 67 | | | | | | {6. 6. 6. 7 | | {3. 4 | | | | | | | | | | | | | | | | | {5. 6. 6. 6. 7 | | | | | | | 21 | 301- 310 | 7. 7. 8 | 4. 4. 3 | 5. 6 | 5 | {6. 6. 6. 5 | {3. 3. 3. 3 | 5. 5. 5. 2. 4 | {3. 4. 3. 5. 5 | {4. 2. 2. 4 | 5. 3. 7 | 1 | 9 | | | | | | | | | {5. 6. 5. 7 | {3. 2 | | {1. 1. 2. 4. 7 | {4. 3 | | | | | | | | | | | | | | | {2. 3. 2. 2. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 311- 320 | {7. 7. 7. 7 | 1. 1. 1. 2. 3 | {5. 5. 4. 2 | 1. 1. 6. 5 | 4. 6. 7 | 1. 3. 2 | {2. 2. 2. 2 | {1. 1. 2. 3 | {2. 2. 2. 4 | {6. 3. 3. 8 | 0 |10 | 1 |19 | 1:19. 00 | | {7. 7. 8 | | {2. 5. 6 | | | | {2. 2. 3. 4 | {6. 6. 6. 8 | {2. 3 | {4. 8. 7 | | | | | | | | | | | | | | | | | | | | | 22 | 321- 330 | 7. 8 | {2. 4. 2. 1. 4 | 6 | 5 | 6. 6. 8. 7 | 3. 2 | 5. 5. 3. 3. 4 | 3. 3. 7. 7. 8 | 4. 4. 4. 2. 3 | 6. 7 | 2 | 8 | | | | | | {4. 4. 4. 3 | | | | | | | | | | | | | " | 331- 340 | 7. 8 | 3 | 6 | 5 | 6. 7 | 3. 2 | 5. 4 | 6. 7. 8 | 3 | 5. 6. 7 | 4 | 6 | 6 |14 | 1: 2. 33 | | | | | | | | | | | | | | | | 23 | 341- 350 | 7. 8 | 4. 2. 4. 3 | 6 | 5 | 6. 7 | {3. 3. 3. 1 | 5. 5. 4 | {7. 5. 4. 3 | 4. 4. 4. 3 | {6. 6. 3. 6 | 2 | 8 | | | | | | | | | | {3. 3. 3. 2 | | {6. 7. 7. 8 | | {8. 6. 8. 7 | | | | | | | | | | | | | | | | | | | | | " | 351- 360 | 7. 8 | 4. 4. 3 | 6 | 6. 5 | 6. 7 | 3. 3. 2 | 5. 4 | {6. 7. 6. 5 | 4. 3 | 5. 6. 7 | 1 | 9 | 3 |17 | 1: 5. 67 | | | | | | | | | {7. 6. 8 | | | | | | | | | | | | | | | | | | | | | | | 24 | 361- 370 | 7. 8 | 4. 4. 2. 3 | 7. 7. 6 | 6. 6. 4. 5 | 7 | {3. 3. 3. 3 | 5. 4 | 8 | 4. 4. 3 | 5. 6. 7 | 2 | 8 | | | | | | | | | | {3. 3. 2 | | | | | | | | | | | | | | | | | | | | | | | | | " | 371- 380 | 8 | 4. 3 | 7. 6 | 5 | 7 | 3. 2 | 5. 4 | 7. 6. 8 | 4. 3 | 7 | 4 | 6 | 6 |14 | 1: 2. 33 | | | | | | | | | | | | | | | | 25 | 381- 390 | 8 | 4. 4. 3 | 7. 7. 7. 6 | {6. 6. 6. 6 | 8. 6. 7 | 3. 1. 2 | 5. 3. 5. 4 | 8 | 3 | 7 | 4 | 6 | | | | | | | | {6. 4. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | " | 391- 400 | 8 | 4. 3 | 6 | 5 | 6. 5. 8. 7 | 3. 2 | 5. 4 | 8 | 3 | 8. 7 | 5 | 5 | 9 |11 | 1: 1. 22 | | | | | | | | | | | | | | | | 26 | 401- 410 | 9. 9. 9. 8 | 3 | {7. 7. 7. 7. 3 | {6. 6. 6. 6 | 8. 8. 8. 7 | 3. 2 | {5. 5. 5. 5 | 7. 8 | {4. 4. 4. 4 | 6. 6. 8. 8. 7 | 1 | 9 | | | | | | | {3. 7. 7. 6 | {6. 6. 5 | | | {5. 5. 4 | | {4. 4. 3 | | | | | | | | | | | | | | | | | | | | | | " | 411- 420 | 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 8. 7 | 3 | 7 | 4 |16 | 1: 4. 00 | | | | | | | | | | | | | | | | 28 | 421- 430 | 8 | {4. 4. 4. 4 | 7. 6 | {6. 6. 3. 6 | 7 | {3. 3. 3. 3 | 5. 5. 5. 4 | 9. 7. 7. 5. 8 | 4. 4. 4. 3 | 8. 7 | 2 | 8 | | | | | | {4. 4. 3 | | {6. 6. 6. 5 | | {3. 3. 2 | | | | | | | | | | | | | | | | | | | | | | | | | " | 431- 440 | 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 7 | 4 | 6 | | | | | | | | | | | | | | | | | | | | | | | | | | | | {7. 6. 5. 4 | | | | | | | " | 441- 450 | 8 | 4. 3 | 7. 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | {3. 2. 1. 5 | 4. 3 | 7 | 2 | 8 | 8 |22 | 1: 2. 75 | | | | | | | | | {7. 9. 8 | | | | | | | | | | | | | | | | | | | | | | | 29 | 451- 460 | 8 | 3 | 6 | 6. 6. 6. 5 | 8. 6. 7 | {3. 3. 3. 3 | 5. 4 | 8 | 4. 3 | 7 | 5 | 5 | | | | | | | | | | {3. 3. 2 | | | | | | | | | | | | | | | | | | | | | | | | | " | 461- 470 | 8 | 4. 3 | 6 | 5 | 8. 7 | 3. 2 | 3. 2. 3. 4 | 7. 8 | 4. 3 | 7 | 4 | 6 | | | " | 471- 480 | 8 | 4. 4. 3 | 7. 7. 6 | 6. 6. 5 | 7 | 2 | 5. 5. 5. 5. 5. 4 | 7. 8 | 4. 4. 3 | 7 | 4 | 6 |13 |17 | 1: 1. 31 | | | | | | | | | | | | | | | | 30 | 481- 490 | 8 | {4. 4. 4. 4 | 7. 7. 6 | 6. 6. 6. 5 | 8. 6. 6. 5. 7 | {3. 1. 3. 3 | 5. 5. 5. 4 | 8 | 4. 4. 4. 3 | 7 | 3 | 7 | | | | | | {4. 4. 3 | | | | {3. 3. 3. 2 | | | | | | | | | | | | | | | | | | | | | | | | | " | 491- 500 | 8 | 4. 3 | 7. 7. 7. 6 | 6. 6. 5 | 8. 8. 7 | 3. 3. 3. 3. 2 | 5. 4 | {9. 9. 7. 4 | 3 | 8. 8. 7 | 2 | 8 | 5 |15 | 1: 3. 00 | | | | | | | | | {9. 6. 8 | | | | | | | July | | | | | | | | | | | | | | | | 1 | 501- 510 | 9. 7. 9. 8 | 4. 3 | 6 | 6. 5 | 8. 6. 7 | 3. 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | | | | | | | | | | | | | | | | | | | " | 511- 520 | {9. 7. 7. 7 | 4. 3 | 7. 6 | 6. 4. 5 | 7 | 3. 2 | 4 | 8 | 4. 4. 4. 3 | 8. 6. 5. 6. 7 | 3 | 7 | 6 |14 | 1: 2. 33 | | {7. 9. 8 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 2 | 521- 530 | 9. 8 | 3 | 7. 5. 7. 6 | 6. 4. 5 | 8. 7 | 2 | 4 | 8 | 3 | 7 | 6 | 4 | | | | | | | | | | | | | | | | | | | " | 531- 540 | 9. 9. 7. 8 | 3 | 7. 4. 6 | 5 | 6. 6. 7 | 3. 3. 2 | 3. 4 | 7. 3. 5. 4. 8 | 4. 3 | {8. 8. 6. 5 | 2 | 8 | 8 |12 | 1: 1. 50 | | | | | | | | | | | {4. 5. 7 | | | | | | | | | | | | | | | | | | | | | 3 | 541- 550 | 8 | 4. 3 | 6 | {6. 6. 6. 6 | 6. 8. 7 | 3. 3. 3. 2 | 5. 5. 4 | 9. 6. 9. 6. 8 | 4. 3 | 7 | 3 | 7 | | | | | | | | {6. 6. 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | " | 551- 560 | 9. 9. 7. 8 | 4. 3 | 6 | 5 | 8. 6. 5. 7 | {3. 3. 3. 3 | 5. 4 | {7. 6. 5. 7 | 3 | 7 | 4 | 6 | 7 |13 | 1: 1. 86 | | | | | | | {3. 2 | | {9. 7. 9. 8 | | | | | | | | | | | | | | | | | | | | | | | 5 | 561- 570 | 8 | 4. 3 | 7. 6 | 6. 5 | {8. 8. 8. 8 | {3. 3. 3. 3 | 5. 5. 5. 5. 4 | 8 | 4. 4. 4. 3 | 8. 8. 8. 8. 7 | 2 | 8 | | | | | | | | | {8. 8. 7 | {3. 3. 3. 2 | | | | | | | | | | | | | | | | | | | | | | | | | " | 571- 580 | 9. 8 | 4. 4. 4. 3 | 6 | 6. 5 | 8. 8. 7 | {3. 3. 3. 3. 3 | {5. 5. 5. 5. 5 | 7. 6. 8 | 4. 4. 3 | 7 | 2 | 8 | 4 |16 | 1: 4. 00 | | | | | | | {3. 3. 3. 2 | {5. 5. 5. 4 | | | | | | | | | | | | | | | | | | | | | | | | 6 | 581- 590 | 9. 8 | 4. 3 | 7. 7. 6 | 6. 6. 5 | 7 | 2 | 5. 4 | 7. 8 | 4. 3 | 7 | 3 | 7 | | | " | 591- 600 | 8 | 3 | 6 | 4. 5 | 6. 6. 6. 7 | 2 | 5. 3. 5. 4 | 8 | 4. 4. 3 | 8. 8. 8. 7 | 5 | 5 | 8 |12 | 1: 1. 50 7 | 601- 610 | 8 | 1. 3 | 6 | 5 | 6. 5. 7 | 2 | 5. 4 | 5. 6. 6. 6. 7. 8 | 4. 3 | 7 | 5 | 5 | | | | | | | | | | | | | | | | | | | " | 611- 620 | {9. 7. 7. 7. 9 | 3 | 6 | 5 | 6. 5. 6. 5. 7 | 3. 2 | 5. 4 | 7. 9. 7. 9. 8 | {4. 4. 4. 4 | 8. 7 | 3 | 7 | 8 |12 | 1: 1. 50 | | {7. 7. 7. 8 | | | | | | | | {4. 4. 4. 3 | | | | | | | | | | | | | | | | | | | | | | 8 | 621- 630 | {9. 9. 9. 7. 9 | 4. 3 | 6 | 6. 6. 6. 5 | {8. 8. 8. 8 | 3. 2 | 5. 4 | 7. 6. 8 | 3 | 7 | 3 | 7 | | | | | {9. 9. 8 | | | | {5. 6. 5. 7 | | | | | | | | | | | | | | | | | | | {7. 6. 5. 7 | | | | | | | " | 631- 640 | 9. 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 4 | {6. 5. 4. 6 | 3 | 7 | 6 | 4 | | | | | | | | | | | | {9. 7. 9. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 641- 650 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7. 9. 6. 7. 9. 8 | 3 | 8. 6. 8. 7 | 8 | 2 |17 |13 | 1: 0. 76 9 | 651- 660 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7. 6. 7. 6. 8 | 3 | 8. 6. 8. 8. 4. 7 | 8 | 2 | | | " | 661- 670 | 9. 9. 8 | 3 | 7. 6 | 5 | 7 | 3. 2 | 5. 4 | 7. 6. 7. 6. 8 | 4. 3 | 5. 6. 8 | 3 | 7 |11 | 9 | 1: 0. 82 | | | | | | | | | | | | | | | | 10 | 671- 680 | 9. 8 | 3 | 5. 4. 5. 6 | 5 | 6. 4. 8. 6. 7 | 3. 2 | {3. 5. 3. 2. 3 | {7. 6. 5. 6 | 3 | 5. 4. 3. 7 | 3 | 7 | | | | | | | | | | | {5. 3. 5. 2. 4 | {5. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 681- 690 | 8 | 4. 3 | 6 | 5 | 7 | 2 | 5. 4 | 8 | 3 | 6. 8. 7 | 7 | 3 |10 |10 | 1: 1. 00 12 | 691- 700 | 7. 8 | 3 | 5. 6 | 5 | 7 | 3. 2 | 3. 4 | 7. 7. 7. 7. 8 | 4. 2. 2. 3 | 8. 7 | 3 | 7 | | | | | | | | | | | | | | | | | | | " | 701- 710 | 9. 8 | 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | {7. 6. 5. 4. 3 | 3 | 8. 7 | 2 | 8 | | | | | | | | | | | | {2. 1. 4. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 711- 720 | 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | {7. 6. 5. 4. 3 | 3 | {6. 5. 4. 3. 6 | 4 | 6 | 9 |21 | 1: 2. 33 | | | | | | | | | {2. 5. 9. 8 | | {5. 4. 3. 8. 7 | | | | | | | | | | | | | | | | | | | | | 13 | 721- 730 | 7. 8 | 4. 3 | 6 | 4. 3. 6. 5 | 4. 6. 5. 4. 7 | 2 | 4 | {6. 5. 4. 3 | 3 | {5. 4. 3. 6 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | {2. 1. 8 | | {8. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {4. 7. 5. 4 | | | | | | | 14 | 731- 740 | 8 | 3 | 5. 5. 6 | 5 | {5. 6. 5. 5 | 3. 2 | 4 | {7. 7. 4. 6 | 3 | 4. 6. 7 | 5 | 5 | | | | | | | | | {8. 8. 7 | | | {5. 6. 8 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {5. 4. 5. 5. 4 | | {4. 4. 4. 5. 5 | | | | | " | 741- 750 | 8 | 3 | 5. 6 | 5 | {6. 5. 6. 6 | 2 | 4 | {5. 6. 4. 4. 4 | 3 | {5. 4. 8. 8. 4 | 6 | 4 |11 | 9 | 1: 0. 82 | | | | | | {6. 8. 4. 7 | | | {7. 6. 8 | | {5. 5. 6. 4. 7 | | | | | | | | | | | | | | | | | | | | | 15 | 751- 760 | 7. 7. 9. 7. 8 | 3 | 6 | 5 | 6. 6. 7 | 2 | 4 | 6. 6. 8 | 3 | {6. 6. 6. 8 | 6 | 4 | | | | | | | | | | | | | | {5. 6. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {5. 4. 6. 6. 5 | | | | | " | 761- 770 | 8 | 3 | 5. 6 | 5 | 6. 6. 6. 6. 7 | 2 | 3. 4 | 5. 4. 7. 8 | 3 | {5. 3. 5. 8. 5 | 5 | 5 |11 | 9 | 1: 0. 82 | | | | | | | | | | | {5. 5. 7 | | | | | | | | | | | | | | {4. 6. 7. 6. 9 | | | | | | | 16 | 771- 780 | 7. 7. 7. 8 | 3 | 6 | 4. 5 | 5. 7 | 2 | 3. 4 | {7. 7. 5. 5 | 3 | (5. 6. 8. 5 | 4 | 6 | | | | | | | | | | | | {6. 6. 6. 8 | | {3. 7 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {6. 6. 7. 2 | | | | | | | " | 781- 790 | 7. 8 | 3 | {4. 5. 4. 3 | {4. 6. 4. 4 | {4. 4. 6. 8 | 2 | 3. 4 | {3. 4. 4. 4 | 3 | 6. 7 | 3 | 7 | 7 |13 | 1: 1. 86 | | | | {2. 6 | {1. 4. 3. 5 | {5. 7 | | | {9. 9. 8 | | | | | | | | | | | | | | | | | | | | | | | 17 | 791- 800 | 7. 8 | 2. 3 | 6 | {4. 4. 4. 3. 6 | 4. 8. 4. 6. 7 | 2 | 4 | {5. 7. 6. 6. 1 | 3 | 5. 7 | 4 | 6 | | | | | | | | {2. 4. 2. 5 | | | | {7. 4. 4. 8 | | | | | | | | | | {2. 4. 4. 4. 2 | | | | | | | | | | | | | " | 801- 810 | 7. 8 | {4. 2. 4. 1. 4 | 5. 7. 6 | 5 | 5. 7 | 2 | 3. 5. 5. 4 | 6. 8 | {2. 4. 4. 2 | 6. 8. 7 | 2 | 8 | 6 |14 | 1: 2. 33 | | | {2. 4. 3 | | | | | | | {4. 2. 4 3 | | | | | | | | | | | | | | | | | | | | | | 19 | 811- 820 | 7. 9. 7. 8 | 2. 4. 2. 4. 3 | 5. 7. 6 | 3. 6. 4. 6. 5 | 7 | 2 | 3. 5. 4 | 6. 8 | 4. 4. 3 | 6. 8. 7 | 2 | 8 | | | " | 821- 830 | 7. 8 | 2. 4. 4. 3 | 6 | 4. 6. 6. 6. 5 | 6. 8. 7 | 2 | 3. 5. 5. 5. 4 | 6. 8 | 2. 4. 3 | 6. 5. 7 | 2 | 8 | | | " | 831- 840 | 7. 9. 8 | 2. 4. 4. 2. 4. 3 | 7. 6 | 5 | 7 | 2 | 4 | 7. 6. 4. 6. 8 | 2. 4. 3 | 6. 8. 7 | 4 | 6 | 8 |22 | 1: 2. 75 20 | 841- 850 | 7. 8 | 3 | 5. 7. 6 | 4. 6. 5 | 6. 8. 7 | 2 | 3. 5. 4 | 3. 5. 8 | 2. 4. 3 | 6. 8. 6. 8. 7 | 2 | 8 | | | " | 851- 860 | 8 | 2. 4. 3 | 6 | 3. 6. 5 | 5. 7 | 2 | 2. 5. 4 | 4. 7. 8 | 2. 4. 3 | 4. 4. 6. 7 | 3 | 7 | | | " | 861- 870 | 7. 8 | 2. 4. 3 | 6 | 5 | 7 | 2 | 2. 4 | 6. 8 | 2. 4. 3 | 4. 7 | 4 | 6 | 9 |21 | 1: 2. 33 21 | 871- 880 | 7. 9. 8 | 2. 4. 3 | 5. 7. 6 | {4. 6. 4. 6 | 4. 6. 7 | 2 | 3. 5. 3. 5. 4 | 5. 7. 8 | 2. 4. 3 | 5. 7 | 1 | 9 | | | | | | | | {3. 2. 4. 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | " | 881- 890 | 7. 8 | 2. 4. 2. 3 | 3. 5. 7. 6 | 3. 4. 6. 4. 6. 5 | 4. 6. 5. 6. 7 | 2 | 4 | 6. 8 | 3 | 4. 6. 5. 7 | 3 | 7 | | | | | | | | | | | | | | | | | | | " | 891- 900 | 7. 8 | 2. 4. 3 | 5. 7. 6 | 4. 5 | 5. 7 | 3. 3. 3. 2 | 4 | {4. 6. 5. 7. 6 | 2. 4. 3 | 5. 7 | 1 | 9 | 5 |25 | 1: 5. 00 | | | | | | | | | {4. 2. 4. 8 | | | | | | | | | | | | | | | | | | | | | | | 22 | 901- 910 | 7. 8 | 2. 4. 3 | 5. 7. 6 | 4. 6. 5 | 6. 8. 7 | 2 | 2. 5. 4 | 5. 6. 8 | 2. 3 | 6. 7 | 1 | 9 | | | " | 911- 920 | 7. 8 | 2. 3 | 5. 6 | 4. 5 | 5. 7 | 2 | 3. 4 | 4. 6. 8 | 2. 3 | 5. 6. 7 | 1 | 9 | 2 |18 | 1: 9. 00 | | | | | | | | | | | | | | | | 23 | 921- 930 | 7. 8 | 2. 3 | {3. 2. 4. 4 | 5 | 4. 6. 5. 6. 7 | 2 | 3. 2. 4 | 5. 4. 6. 8 | 2. 3 | {4. 5. 4. 3. 5 | 2 | 8 | | | | | | | {5. 6 | | | | | | | {6. 5. 6. 7 | | | | | | | | | | | | | | | | | | | | | 23 | 931- 940 | 7. 9. 7. 8 | 3 | 5. 4. 6 | 5 | 5. 7 | 2 | 4 | 6. 7. 8 | 3 | 6. 8. 7 | 5 | 5 | | | " | 941- 950 | 7. 8 | 3 | 5. 6 | 4. 6. 5 | 7 | 2 | 3. 5. 4 | 5. 6. 8 | 2. 3 | 6. 7 | 3 | 7 |10 |20 | 1: 2. 00 | | | | | | | | | | | | | | | | 24 | 951- 960 | 7. 8 | 2. 3 | {2. 7. 7. 4 | 4. 6. 5 | 5. 7 | 2 | 4 | 4. 6. 8 | 3 | 6. 8. 7 | 3 | 7 | | | | | | | {5. 7. 4. 6 | | | | | | | | | | | | | | | | | | | | | | | | | | | | " | 961- 970 | 7. 9. 7. 8 | 3 | 6 | 5 | (6. 8. 6. 8 | 2 | 5. 5. 3. 4 | 7. 8 | 3 | 7 | 6 | 4 | 9 |11 | 1: 1. 22 | | | | | | {6. 7 | | | | | | | | | | | | | | | {4. 2. 6. 4 | | | | | | | | | | | 26 | 971- 980 | 7. 9. 7. 8 | 3 | 6 | {6. 4. 6. 4 | 7 | 2 | 4 | 6. 8 | 3 | 6. 8. 7 | 6 | 4 | | | | | | | | {6. 1. 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | " | 981- 990 | 7. 9. 7. 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7. 6. 8 | 3 | 6. 8. 7 | 7 | 3 | | | | 991-1000 | 7. 8 | 3 | 6 | 5 | 6. 8. 5. 7 | 2 | 4 | 6. 8 | 4. 2. 3 | 6. 5. 7 | 5 | 5 |18 |12 | 1: 0. 67--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- In |trials 1001| to 1100 the | right door |was indicated | by being |raised before | the choice | was made. | | | | | | | |--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- 30 | 1101-1110 | 8 | 4. 3 | 7. 6 | 6. 6. 5 | 7 | 2 | 5. 4 | {7. 7. 7. 7. 7 | 3 | 6. 6. 7 | 4 | 6 | 4 | 6 | 1: 1. 50 | | | | | | | | | {7. 6. 6. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {7. 7. 6. 7 | | | | | | | 31 | 1111-1120 | 7. 7. 8 | 3 | 7. 6 | 5 | 6. 7 | 3. 3. 2 | 4 | {7. 6. 6. 7 | 4. 4. 4. 3 | 7 | 4 | 6 | | | | | | | | | | | | {6. 6. 8* | | | | | | | | | | | | | | | | | | | | | | | " | 1121-1130 | 8 | 4. 3 | 6 | 6. 5 | 8. 7 | 3. 2 | 5. 4 | 7. 8 | 3 | 7 | 4 | 6 | 8 |12 | 1: 1. 50 August | | | | | | | | | | | | | | | | 2 | 1131-1140 | 8 | 4. 4. 3 | 6 | 5 | 7 | 3. 3. 3. 2 | 4 | 7. 8 | 4. 3 | 7 | 6 | 4 | | | " | 1141-1150 | 7. 8 | 4. 4. 3 | 7. 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 4. 3 | 7 | 3 | 7 | 9 |11 | 1: 1. 22 3 | 1151-1160 | 7. 9. 8 | 4. 3 | 7. 6 | 5 | 6. 7 | 2 | 5. 4 | 7. 6. 7. 8 | 4. 3 | 6. 7 | 2 | 8 | | | " | 1161-1170 | 8 | 4. 3 | 6 | 5 | 7 | 2 | 5. 4 | 7. 8 | 4. 3 | 7 | 6 | 4 | 8 |12 | 1: 1. 50 4 | 1171-1180 | 8 | 4. 3 | 6 | 6. 5 | 6. 7 | 3. 2 | 5. 4 | 7. 8 | 4. 3 | 6. 5. 6. 7 | 2 | 8 | | | " | 1181-1190 | 8 | 3 | 6 | 5 | 7 | 3. 3. 2 | 4 | 7. 8 | 3 | 7 | 8 | 2 |10 |10 | 1: 1. 00 5 | 1191-1200 | 7. 8 | 4. 4. 3 | 6 | 5 | 6. 7 | 3. 3. 3. 2 | 4 | 6. 7. 8 | 3 | 7 | 5 | 5 | | | | 1201-1210 | 8 | 4. 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 7. 8 | 3 | 7 | 5 | 5 | | | " | 1211-1220 | 7. 8 | 3 | 7. 6. 5 | 5 | 7 | 2 | 4 | 7. 7. 6. 7. 8 | 3 | 7 | 7 | 3 |17 |13 | 1: 0. 76 | | | | | | | | | | | | | | | | 6 | 1221-1230 | 8 | 3 | 6 | 5 | {6. 5. 6. 6 | 2 | 4 | {5. 6. 5. 7 | 3 | 6. 8. 6. 7 | 7 | 3 | | | | | | | | | {5. 6. 5. 7 | | | {9. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | " | 1231-1240 | 7. 8 | 3 | 6 | 4. 5 | 7 | 2 | 4 | 6. 7. 8 | 3 | 6. 7 | 6 | 4 |13 | 7 | 1: 0. 54 7 | 1241-1250 | 7. 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 8. 7 | 8 | 2 | | | " | 1251-1260 | 8 | 3 | 6 | 6. 5 | 7 | 3. 2 | 5. 4 | 8 | 3 | 7 | 7 | 3 | | | " | 1261-1270 | 8 | 3 | 6 | 5 | 7 | 3. 2 | 5. 3. 4 | 8 | 3 | 7 | 8 | 2 |23 | 7 | 1: 0. 30 9 | 1271-1280 | 8 | 3 | 6 | 5 | 7 | 2 | 5. 4 | 9. 7. 8 | 3 | 7 | 8 | 2 | | | " | 1281-1290 | 8 | 3 | 6 | 5 | 7 | 3. 2 | 4 | 7. 8 | 3 | 7 | 8 | 2 |16 | 4 | 1: 0. 25 10 | 1291-1300 | 7. 8 | 3 | 7. 6 | 5 | 6. 7 | 3. 2 | 4 | 6. 7. 8 | 3 | 7 | 5 | 5 | | | " | 1301-1310 | 7. 8 | 4. 3 | 5. 6 | 4. 5 | 6. 7 | 2 | 4 | 6. 8 | 3 | 6. 8. 7 | 3 | 7 | | | " | 1311-1320 | 7. 8 | 3 | 6 | 5 | 5. 7 | 2 | 4 | 5. 7. 8 | 3 | 4. 6. 8. 7 | 6 | 4 |14 |16 | 1: 1. 14 11 | 1321-1330 | 7. 8 | 3 | 6 | 5 | 6. 7 | 3. 2 | 4 | 4. 6. 7. 8 | 2. 3 | 5. 7 | 4 | 6 | | | " | 1331-1340 | 7. 8 | 3 | 6 | 4. 5 | 6. 7 | 2 | 4 | 6. 7. 8 | 3 | 7 | 6 | 4 |10 |10 | 1: 1. 00 12 | 1341-1350 | 9. 8 | 3 | 6 | 5 | 6. 7 | 2 | 4 | 6. 7. 8 | 3 | 6. 7 | 6 | 4 | | | " | 1351-1360 | 7. 8 | 3 | 6 | 5 | 6. 7 | 2 | 4 | 7. 8 | 3 | 6. 7 | 6 | 4 |12 | 8 | 1: 0. 67 19 | 1361-1370 | 7. 8 | 3 | 6 | 5 | 6. 7 | 2 | 4 | 6. 7. 8 | 3 | 6. 7 | 6 | 4 | | | | 1371-1380 | 9. 8 | 3 | 6 | 5 | 7 | 3. 2 | 4 | 7. 9. 8 | 3 | 6. 8. 7 | 6 | 4 |12 | 8 | 1: 0. 67========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

[Footnote *: Aided by experimenter. ]

After two hundred and fifty trials on problem 2 had been given Julius, it seemed desirable to introduce a radical change in method in order tostimulate him to maximal effort. It was therefore decided to force himto make a round trip through the apparatus in connection with eachchoice, and to let this forced labor serve, in the place of confinement, as punishment for mistakes. This new method yielded peculiar andcharacteristic results. They differ from those previously obtainedlargely because of the orang utan's remarkably strong tendency toreenter the box through which he had just passed. This occurred sopersistently, as may be seen in table 9 (June 17, second series, June18, etc. ), that a further modification of method was introduced in thatafter the same wrong box had been entered five times in succession, theexperimenter on the next choice of the box confined the animal for astated interval, say sixty seconds, in it, and then allowed it to escapeby way of the exit door and choose repeatedly until it finally locatedthe right box. Were it not for this particular feature of the method, the number of choices recorded after June 17 would unquestionably bevery much greater than the table indicates. 

The new method proved a severe test of the orang utan's patience andperseverance, for he had to work much harder than formerly for hisreward, and often became much fatigued before completing the regularseries of ten trials. Early in the use of this method, he developed thehabit of rolling around from exit door to starting point by a series ofsomersaults. When especially discouraged he would often bump his headagainst the floor so hard that I could hear the dull thud. As has beennoted, I found it desirable to vary the procedure repeatedly. It provedespecially interesting to give one series per day with the round trip aspunishment and another series with confinement as punishment. 

Day after day, as the experiment progressed, slight or greatfluctuations of the ratios of right to wrong choices appeared, butwithout consistent improvement. There was, to be sure, as the lastcolumn of table 9 shows, a radical improvement during the first sixhundred and fifty trials, for the number of right choices per seriesincreased from 0 to 8. But, as the observations were continued from dayto day, it became more and more evident that the animal was merelypassing from tendency to tendency--method to method--mixing tendencies, and occasionally developing new ones, without approach to the solutionof the problem. This fact would have led me to discontinue the work muchearlier than I actually did had it not been for the peculiarity of theresults obtained with problem 1. It seemed not improbable that at anytime Julius might succeed in perfectly solving this problem over nightprecisely as he had solved the first problem. 

A curiously interesting bit of behavior appeared for the first time onJune 29. Julius had gone to the first box at the right end of the group, and instead of entering, he had wheeled around toward his right, andturning a complete circle, faced the right box, which he promptlyentered. Subsequently, the tendency developed and the method was usedwith increasing frequency. On June 30, it appeared in the first series, four times, in the second series, six times; on July 1, in the firstseries, three times, and in the second series, four times; on July 2, inthe first series, five times, and in the second series, nine times. Itwas indeed only by accident that the animal failed to fulfill thetechnical requirement for perfect solution of the problem in thisseries. Yet, had he done so, his subsequent trials would doubtless haverevealed the lack of any other idea than that of turning completelyaround before entering a box. 

This odd bit of behavior proved peculiarly interesting and significantin that the tendency to turn became dissociated from the position (infront of the first box at the right end of the group) in connection withwhich it originally developed. After a few days, Julius would enter thereaction-chamber and instead of proceeding directly to the right end ofthe group, would stop suddenly wherever he happened to be, turn towardhis right in a complete circle, and hasten into the box nearest to himwhich, as often as not, proved to be the wrong one. Thus the idea ofturning completely about, which had it continued its association withthe idea of facing the first box at the right, would have yieldedsuccess, instead became useless because of its dissociation. That theorang utan is capable of using free ideas seems clear enough in thelight of this behavior. That he proved incapable of getting the idea ofsecond from the right end is as clearly shown by the detailed results oftable 9, --the fruits of weeks of experimenting. 

Certain other interesting tricks developed in Julius's behavior. Thus, on July 5, there appeared the tendency to move as though about to enterthe right box (feint), then to stop suddenly and promptly enter anotherbox, which was, of course, a wrong one. The reason for the developmentof this tendency could not be discovered, but in connection with it, there appeared another tendency which possibly can be explained. Juliustook to backing into the chosen box so that he could face theexperimenter. He would then, after a period of hesitation, come out andpromptly enter one of the other boxes. This tendency was apparently dueto the fact that during one or two series the experimenter growled atthe orang utan every time he made a mistake. The growl startled him andcaused him to look around. He evidently felt the need of keeping hiseyes on the experimenter, --Hence the backing into the open box. Thetendency disappeared shortly after the experimenter gave up the use ofthe growl as a method of punishing the animal for what were suspected tobe careless choices. 

Curiously enough, it was not until July 10 that direct choice of theright box was made at all frequently. Previously, selection of it hadbeen made almost invariably after approach to other boxes. But in thesecond series for July 10 there was an extraordinary improvement inmethod. This developed in the presence of two visitors, and it istherefore all the more surprising. The choices were made not onlydirectly, but with decision and evident certainty that was quite atvariance with the previous behavior of the animal. 

All the while through variation of methods, I was seeking to discoverthe best means of holding the orang utan to his maximum effort and carein attempting to select the right box. One day it would seem as thoughforcing him to make round trips with rewards only for correct firstchoices proved most satisfactory, and the next it might seem equallyclear that punishment by confinement for thirty seconds or sixtyseconds, with reward for correct choice in every trial, yielded betterresults. In the end I had to admit that no best method had beendemonstrated and that I had failed to develop conditions which served tocompel the animal's attention to the problem and to lead him to workwithout discouragement. There were, it is true, days on which it seemedpractically certain that the problem would be solved, but as it turnedout, Julius never succeeded in choosing correctly--throughout a seriesof ten trials. 

As a last resort, in order to make perfectly sure that the orang utanwas doing his best, I decided to introduce corporal punishment in a mildform. For this purpose, I placed my assistant in charge of the apparatusand the series of trials, and stationed myself in one corner of thereaction-chamber with a whip in my hand. Whenever Julius entered a wrongbox, I approached him with the whip and struck at him, being careful notto injure him and rarely striking him at all, for the threat was moreeffective than a blow. He was extremely afraid of the whip and wouldbegin to whine and attempt to get out of the way as soon as he saw it. 

This method was introduced on August 10, but no improvement resulted, and in the end there was no reason to consider it more satisfactory thanthe other procedures. I am now wholly convinced that Julius did his bestto choose correctly in the majority of the numerous series which weregiven him in connection with problem 2. 

From trials 1001 to 1100, a radical departure from the previous methodswas introduced in that the right box was indicated to the animal by theslight and momentary raising of its exit door. Of course no records ofthe choices for this group of one hundred trials appear in table 9, forthe simple reason that the animal inevitably and immediately entered theright box. It was thought that this method might serve to break up thepreviously developed tendencies toward inadequate forms of response andso encourage the animal that he would later solve the problem when givenopportunity to select the right box without aid from the experimenter. But as a matter of fact, while the ratio of right to wrong first choiceswas 1 to . 67 in the series preceding this change of method, it was 1 to1. 50 in the first series following its use. There is no satisfactoryevidence that Julius profited by this experience, though as a matter offact he did succeed in making his best daily record, eight right to twowrong choices, on August 4, after 1190 trials. 

The curve of learning for this problem has been plotted and is presentedin figure 19. It is of course incomplete and it is offered only toindicate the extreme irregularity in performance. 

_Problem 1a. First at the Right End_

It was decided on August 19 that the further continuation of the work ofJulius on problem 2 was not worth while. He had become much discouraged, and although willing to work for food, gave no indications whatever ofimprovement and seemed to have exhausted his methods. It seemed wiseinstead of giving up work with him in the multiple-choice method toreturn to a form of problem 1. We may designate it as problem 1a. Theright box is definable as the first at the right end of the seriesinstead of the first at the left end as in the original problem 1. Itwas thought possible that Julius might quickly solve this problem by aprocess similar to that used for problem 1. 

Work was begun on problem 1a, August 20, and for six successive days twoseries of trials per day were given, the settings for which as well asthe resulting choices are given in table 10. Most notable in theseresults is the large number of cases in which Julius chose first thesecond box from the right end of the series, or in other words that boxwhich had been the right one in problem 2. Contrary to expectation, heshowed no inclination to abandon this tendency to choose the second fromthe right end, and the ratio of right to wrong choices changed in thedirection opposite from expectation, beginning with 1 to 4 and ending onthe sixth day with 0 to 20. 

It was obviously useless to continue the experiment further since Juliushad given up his attempts to locate the right box in the first choiceand was apparently satisfied to discover it by a process of trial anderror. He had, it would seem, satisfied himself that the problem wasinsoluble. These results obtained in problem 1a constitute a mostinteresting comment on the effects of problem 2 on the orang utan. Behavior similar to that which he developed well might have beenobtained from a child of three to four years placed in a like situationand forced to strive, day after day, to solve a problem beyond itsideational capacity. 

In many respects the most interesting and to the experimenter the mostsurprising result of this long series of observations with Julius wasthe lack of consistent improvement. It seemed almost incredible that heshould continue, day after day, to make incorrect choices in aparticular setting while choosing correctly in some other setting whichfrom the standpoint of the experimenter was not more difficult. 

TABLE 10

Results for Orang utan in problem 1a

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== | No. | S. 1 | S. 2 | S. 3 | S. 4 | S. 5 | S. 6 | S. 7 | S. 8 | S. 9 | S. 10 | | | | | Ratio Date | of | | | | | | | | | | 1. 2. 3. 4 | R | W | R | W | of | trials | 5. 63 | 1. 2. 3. 4 | 6. 7. 8. 9 | 2. 3. 4. 5 | 3. 4. 5. 6. 7 | 1. 2. 3 | 5. 6. 7. 8 | 1. 2 | 2. 3. 4. 5. 6 | 5. 6. 7 | | | | | R to W--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- | | | | | | | | | | | | | | | | August | | | | | | | | | | | | | | | | 20 | 1- 10 | 6 | 3. 4 | 6. 7. 8. 9 | 4. 5 | 6. 7 | 3 | 7. 8 | 2 | 5. 5. 6 | 6. 7 | 3 | 7 | | | | | | | | | | | | | | | | | | | " | 11- 20 | 5. 6 | 3. 4 | {7. 8. 7. 8 | 4. 5 | 6. 7 | 2. 3 | {7. 6. 7. 7 | 2 | 5. 6 | 6. 7 | 1 | 9 | 4 |16 | 1: 4. 00 | | | | {8. 7. 8. 9 | | | | {6. 7. 7. 8 | | | | | | | | | | | | | | | | | | | | | | | | 21 | 21- 30 | 5. 6 | 3. 4 | {7. 8. 7. 6 | 4. 5 | 6. 7 | 2. 3 | 7. 8 | 2 | 5. 6 | 5. 7 | 1 | 9 | | | | | | | {8. 7. 9 | | | | | | | | | | | | | | | | | | | | | | | | | | | | " | 31- 40 | 5. 6 | 3. 4 | 7. 7. 6. 8. 9 | 4. 5 | 6. 7 | 3 | 6. 7. 8 | 2 | 6 | 6. 7 | 3 | 7 | 4 |16 | 1: 4. 00 23 | 41- 50 | 5. 6 | 3. 4 | 7. 8. 9 | 4. 5 | 6. 7 | 2. 3 | 6. 7. 8 | 2 | 5. 6 | 5. 6. 7 | 1 | 9 | | | " | 51- 60 | 5. 6 | 3. 4 | 7. 8. 9 | 4. 5 | 6. 7 | 2. 3 | 6. 8 | 2 | 5. 6 | 6. 7 | 1 | 9 | 2 |18 | 1: 9. 00 24 | 61- 70 | 5. 6 | 3. 4 | 6. 8. 9 | 4. 5 | 5. 7 | 2. 3 | 6. 7. 8 | 1. 2 | 5. 6 | 6. 7 | 0 |10 | | | " | 71- 80 | 5. 6 | 3. 4 | 6. 7. 8. 9 | 4. 5 | 5. 7 | 2. 3 | 5. 7. 8 | 2 | 5. 6 | 6. 7 | 1 | 9 | 1 |19 | 1:19. 00 25 | 81- 90 | 5. 6 | 3. 4 | 6. 7. 8. 9 | 5 | 5. 6. 7 | 2. 3 | 7. 8 | 1. 2 | 5. 6 | 4. 5. 6. 7 | 1 | 9 | | | " | 91-100 | 5. 6 | 3. 4 | 6. 7. 8. 9 | 3. 4. 5 | 6. 6. 7 | 2. 3 | 6. 7. 8 | 1. 2 | 5. 6 | 6. 7 | 0 |10 | 1 |19 | 1:19. 00 | | | | | | | | | | | | | | | | 26 | 101-110 | 5. 6 | 3. 4 | {6. 7. 8. 8 | 3. 5 | 5. 6. 7 | 2. 3 | 5. 6. 7. 6. 7. 8 | 1. 2 | 5. 6 | 6. 7 | 0 |10 | | | | | | | {6. 7. 6. 9 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | {6. 7. 8. 8 | | | | | | | | | | | | " | 111-120 | 5. 6 | 2. 3. 4 | {6. 7. 8. 7 | 3. 4. 5 | 5. 6. 7 | 2. 3 | 7. 8 | 1. 2 | 5. 6 | 4. 5. 6. 7 | 0 |10 | 0 |20 | 0:20. 00 | | | | {6. 7. 9* | | | | | | | | | | | | | | | | | | | | | | | | | | | |========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========

[Footnote *: Aided by experimenter. ]

The evidence suggests that in this young orang utan ideational learningtended to replace the simpler mode of problem solution by trial anderror. Seemingly incapable of solving his problems by the lower gradeprocess, he strove persistently, and often vainly, to gain insight. Heused ideas ineffectively. Animals far lower in intelligence (e. G. , thepig), surpass him in ability to solve these relational problems becausethey use the method of elimination by trial consistently andeffectively. Julius, in these experiments, made a poor showing becausehis substitute for trial and error is only slightly developed. Would hehave succeeded better with the same problems if mentally mature?

There are many important features of the results which, for lack ofspace, have not been indicated or discussed. They can be developed fromlater comparative studies of the data, for in the tables appear all ofthe essential facts of response apart from those mentioned in the text. 

IV

RESULTS OF SUPPLEMENTARY TESTS OF IDEATIONAL BEHAVIOR

1. Julius, _Pongo pygmaeus_

_Box Stacking Experiment_

In addition to the multiple-choice experiments which have been describedin detail in the previous section, it was possible to conduct certainless systematic tests of ideational behavior in the monkeys and theorang utan. From the technical standpoint these tests were relativelyunsatisfactory because only inexactly describable. But their results arein many respects more interesting, if not also more important, in thelight which they throw on ideation than are those previously presented. First, in order of time, comes a test which may be designated as the boxstacking experiment. The method will now be described in connection withan account of the behavior of Julius as contrasted with that of a childof three years and four months of age. 

In the large central cage labelled Z, figure 12, which was twenty-fourfeet long, ten feet wide, and ten to twelve feet deep, the followingsituation was arranged. From the center of the wire covering of thecage, a banana was suspended on a string so that it was approximatelysix feet from the floor, five feet from either side of the cage, andtwelve feet from either end. From all approaches it was far beyond thereach of Julius, since it was impossible for him to climb along the wireroof and thus reach the string. Two boxes were placed on the floor ofthe cage several feet from the point directly under the banana. The oneof these boxes was heavy and irregular in shape, as is shown in figures21, 23 and 24 of plate V. Its greatest height was twenty-one inches; itsleast height, eighteen inches; its other dimensions, twelve and sixteeninches respectively. The smaller and lighter box measured twenty-two bytwelve by ten inches. According to the experimenter's calculations, theonly way in which Julius could obtain the banana was by placing thesmaller box upon the larger and then climbing upon them. 

At 10 a. M. On March 5, Julius was admitted to the large cage, and thebanana was pointed out to him by the experimenter. He immediately setabout trying to get it, and worked diligently during the whole of theperiod of observation, which, because of the unfinished condition ofsome of the cages, was limited to slightly over ten minutes. Within thisperiod he made upward of a dozen fairly well directed attempts to obtainthe food. Chief among them were three attempts to reach the banana fromdifferent positions on the left wall of the cage (as the experimenterfaced the laboratory); two attempts to reach it from different positionson the right wall; two from the large box in positions nearly under thebanana; two from the large box with the aid of the experimenter's hand;and one from the distant end of the cage(?). There occurred, also, lessdefinite and easily describable efforts to get at the reward. 

On account of the unfinished condition of the cages, the experimenterhad to remain in the large cage with Julius during the test. Thisinterfered with the experiment because the animal tended both to try toescape and to get the experimenter to help him with his task. Particularly interesting is the latter sort of behavior. After the orangutan had made two or three futile attempts to obtain the food he came tothe experimenter, who was standing in one corner of the cage, took himby the hand, and led him to a point directly under the banana. He thenlooked up toward the banana, grasped the experimenter's arm, raised it, and then tried to pull himself up. He was not allowed to get the food byclimbing up on the experimenter. A few minutes later, he again led theexperimenter toward the banana, but receiving discouragement in thisactivity, he proceeded to devote himself to other methods. 

Apart from the distractions which have been mentioned above, Julius'sattention to the food was surprisingly constant. Whatever his positionwith respect to it, he seemed not for an instant to lose his motive, andto whatever part of the cage he went and whatever he did during theinterval of observation was evidently guided by the strong desire toobtain the banana. Frequently he would look directly at it for a fewseconds and then try some new method of reaching it. His gaze wasdeliberate and in the handling of the boxes he accurately gaugeddistances. Several times he succeeded in placing the larger box almostdirectly under the banana, and repeatedly he located that portion of theside wall from which he could most nearly reach the coveted prize. 

EXPLANATION OF PLATE V

Orang utan, Julius, obtaining banana by piling boxesor by using pole

FIGURE 21. --Julius in act of setting larger box on end. 

FIGURE 22. --Placing smaller box on larger. 

FIGURE 23. --Balancing on larger box preparatory to reaching for banana. 

FIGURE 24. --Balancing and reaching to the utmost. 

FIGURE 25. --Standing on three boxes (after stacking them) andreaching for reward. 

FIGURE 26. --Lifting smaller box up toward banana. 

FIGURE 27. --The act of stacking the boxes. 

FIGURE 28. --Sequel to figure 27. 

FIGURE 29. --Box and pole experiment. Pushing the second poleinto the box. 

FIGURE 30. --Pushing pole into box. 

FIGURE 31. --Enjoying the reward of success. 

From my notes I quote the following comment on the results of theinitial experiment: "Despite all that has been written concerning theintelligent behavior of the orang utan, I was amazed by Julius'sbehavior this morning, for it was far more deliberate and apparentlyreflective as well as more persistently directed toward the goal than Ihad anticipated. I had looked for sporadic attempts to obtain thebanana, with speedy discouragement and such fluctuations of attention aswould be exhibited by a child of two to four years. But in less than tenminutes Julius made at least ten obvious and well directed attempts toreach the food. There were also wanderings, efforts to obtain aid fromthe experimenter, and varied attempts to escape from the cage. "

Before proceeding further with the description of the behavior of Juliusin the box stacking test, I shall describe for contrast the behavior ofa boy three years four months of age when confronted with a situationpractically identical with that which the ape was given an opportunityto meet. For the child, the banana was suspended, as previouslydescribed, from the roof of the cage. The same two boxes were placed onthe floor at considerable distances from the banana, and in addition, alight stick, about six feet long, and a piece of board, the latter byaccident, were on the floor. The child was asked to get the banana forJulius, and he eagerly and confidently volunteered to do so. 

His behavior may best be described by enumeration of the severalattempts made. They include (1) placing the larger box nearly under thebanana and reaching from it. (2) Standing of the larger box on end withresulting failure because the child could not stand on the sloping edgesof the top of the box. (3) The larger box was turned on its side and thelighter box drawn up opposite it and stood on end. The child thenmounted the larger box and from it stepped to the top of the smaller. But the boxes had not been placed beneath the banana, and when the childreached for it, he found himself several feet away from his prize. (4)The boxes were moved to a position nearly under the banana and anotherfutile attempt was made to reach it without placing the smaller box ontop of the larger one, the only position from which the child couldreadily obtain it. (5) The piece of board was placed on top of thelarger box and from this height the child again reached upward. (6) Thesix-foot stick was taken up and an attempt was made to strike the bananaand thus dislodge it, but it was too securely fastened to be obtainedthus. (7) Attention shifted to other things, and the child played for atime with the board. Reminded of the banana by the experimenter, heagain tried method (3). (8) He again used the stick on the banana. (9)The effort to knock the prize to the floor having failed, he becamediscouraged and said that he must go home. (10) When told that Juliuswas very hungry and wanted the banana, he repeated efforts similar tothose described in (3) and (6). 

Up to this time the observations had covered a period of twenty minutes. The child was now taken from the cage and allowed to play about forfifteen minutes. Asked then whether he would go back and try to get thebanana, he replied, "No, 'cause I don't want to get it, " thus indicatinghis discouragement with the situation. When taken into the cage, he, nevertheless, made the additional attempts indicated below: (11) Use ofone of the boxes. (12) He remarked, "Now I know, I'll get it, " and afterso saying, repeated (3). (13) Failing, he turned to me and said, "Icould get it if I was on your head, " but he did not, as Julius had done, lead me to the proper place and try to reach the banana by climbing upor by urging me to lift him. (14) Later, he played in the boxes, apparently forgetful of his task. Finally he remarked: "I'll get thebanana, " but he made no attempt to do so, and instead, watched themonkeys intently. Thereafter, he showed no further interest in thesolution of the problem, and the experiment, after a total period offifty-five minutes, was discontinued. 

Comparison of the behavior of the ape with that of the child indicates agreater variety of ideas for the latter. Julius gauged his distancesmuch more accurately than the child, attended more steadily, and workedmore persistently to obtain the reward, but he did not so nearlyapproach the idea of stacking the boxes as did the child, for thelatter, in placing the board on one of the boxes, exhibited inineffective form the idea which should have yielded the solution of theproblem. 

The child was given no further opportunity to work at the problem, whereas Julius, as I shall now describe, continued his efforts onsubsequent days under somewhat different conditions. On Wednesday, March10, the banana was suspended as formerly, and three boxes, all of themsmall and light enough to be readily handled by the ape, were placed indistant parts of the cage. The six-foot stick which had been present inthe test with the child, but not in the first test with Julius, was alsoplaced in the cage. 

Julius was allowed to work for about an hour. As formerly, he wassufficiently hungry to be eager to get the food and evidently tried allof the possible ways which occurred to him. Chief among these were (1)the use of the various boxes separately or in pairs in very variedpositions but never with one upon another, --the only way in which thebanana could be reached; (2) climbing to various points on the sides ofthe cage, with infrequent attempts to reach the banana. Usually his eyessaved him the vain effort. 

Unlike the child, Julius paid little attention to the six-foot stick. Two or three times he took it up and seemingly reached for the banana, but in no case did he try persistently to strike it and knock it fromthe string. It is but fair, however, to remark that such an act is verydifficult for the young orang utan, as compared with the child, becauseof the weakness of the legs and the awkwardness of striking from asitting posture. As previously, the steadiness of attention and thepersistence of effort toward the end in view were most surprising. Atone time Julius walked to the end of the cage and there happened to seeone of the monkeys eating. He watched intently a few seconds and thenhastened back to the banana as if his task had been suggested to him bythe sight of the feeding animal. Most interesting and significant inthis behavior was the suddenness with which he would turn to a newmethod. It often looked precisely as though a new idea had come to him, and he was all eagerness to try it out. 

On March 11, Julius was given another opportunity to obtain the bananaby the use of the three boxes. Although he used them together he made noeffort to place one upon another. Certain of his methods are shown inplate V, especially by figures 21, 23 and 24. 

This experiment was continued on April 2 under yet different conditions, for this time only two boxes were placed in the cage, the one of themthe heavy, irregularly-shaped box and the other the smaller, lighter oneoriginally used. On the end of the heavier box had been nailed a two bytwo inch wooden block in order to increase the difficulty in using thisbox alone. As previously, Julius made varied attempts to obtain thebanana, but on the whole his interest and attention seemed somewhatweaker than previously and there were indications of discouragementbecause of repeated failures. 

He handled the boxes conspicuously well, and it seemed at times that hewould certainly succeed in placing the one upon the other and inreaching the food. 

After one series of attempts from the sides of the cage and from thelarge box, he deliberately turned away from the box and neatly executeda somersault on the floor of the cage, as much as to say, "I amdisgusted with the whole situation. " Again, later on the same day, afterfalling from the top of the larger box, which tilted over very easily, he rolled himself into a ball, and childlike, played with his feet. Anadditional evidence of his changed affective attitude toward his task, especially in connection with definite failures, appeared in his roughhandling and biting of the boxes. When most impatient, he worked veryroughly. 

Julius was allowed to work for the reward from thirty to ninety minutes, or, as a rule, until he had become completely discouraged on April 3, 5, 6, 7, 8, 9 and 13. His behavior was interesting and significant, butnothing new appeared except that his willingness to work graduallydisappeared, and on April 13, although previously hungry, he made only asingle attempt to obtain the banana and then paid no further attentionto it. 

The prolonged and varied efforts to obtain the banana were due in ameasure at least to three accidental successes. Thus on April 2, 3 andagain on the 5th, by fortunate combinations of circumstances, hesucceeded in getting the banana, contrary to the intention of theexperimenter. 

Although active at first on April 6, he soon wearied of his task andquit work. The same was true on April 7, and again on the 8th and 9th. On these days, although hungry, he did not care to enter the large cageand worked only a few minutes each day, seldom making more than two orthree half-hearted attempts to obtain the banana. His attitude towardthe task had changed completely, in that hopelessness had taken theplace of eager expectancy. By the 13th of April he had so nearly givenup voluntary efforts to solve the problem that it seemed worth while totest his ability to get the idea by watching the experimenter. For thispurpose the following test of imitation was made. 

On the morning of April 14, having placed a banana in the usualposition, I took Julius into the large cage, dragged the two boxes tothe proper position beneath the banana, placed the smaller one upon thelarger one and then climbed up on them to show the ape that I couldreach the banana. I then stepped down and gave him a chance to climb onthe boxes. He did so immediately and obtained the food. 

Another piece of banana was supplied, the boxes were placed in distantcorners of the cage, and fifteen minutes were allowed Julius so to placethem that he could obtain his reward. He gave no indications of havingprofited by my demonstration, but worked with the boxes singly, usuallywith the larger one. On April 16, with the banana in position and thetwo boxes also in the cage, Julius was admitted and allowed to work forfive minutes, but again without success. I then placed the boxesproperly for him and he immediately climbed up and got the banana. Whilehe was eating, the boxes were carried to distant corners of the cage andanother banana placed in position. Now thirty minutes were allowed himfor unaided work on the problem. As formerly, the larger box was usedrepeatedly and attempts to reach from the side of the cage appeared, butthere was no tendency to try to use the two boxes together. He workedfairly persistently, however, and showed clearly the stimulating andencouraging effect of aid from the experimenter. Once more, on April 17, Julius was taken into the cage and allowed to watch me place the boxesin proper position. He then climbed up and obtained the desired food. After the bait had been renewed and the boxes displaced, he immediatelytried to use the larger one, then he reached for the small one as thoughto use both together. But the impulse died out and he turned again tothe larger box as usual, standing it on end, and persistently trying tobalance himself on it. Nothing else of special interest happened duringthe interval of unaided effort. 

Similarly, I placed the boxes for the ape on April 19, allowed him toget the banana and then gave him opportunity to try for himself afterthe boxes had been displaced. This time he immediately reached for thesmaller box and moved it about a little, thus indicating a newassociation. He next turned to the larger box and worked with itpersistently. Later, he once more worked with the smaller box in anunusual manner. He repeatedly stood on it, but made no attempt to liftit or to place it on the larger box. Clearly the usually neglectedsmaller box had become associated with the satisfaction of obtaining thebanana. The same method was carried out on April 20. As I placed theboxes in position beneath the banana, Julius watched with unusualintentness, and when it came his turn to try to obtain the food by theuse of the boxes, he began at once to work with the smaller box, but ason April 19, he soon abandoned it and turned to the other. While I wasmaking note of this particular feature of his behavior, he suddenlyseized the smaller box by two corners with his hands and by one edgewith his teeth, and after a few attempts placed it on top of the largerbox, climbed up, and obtained the banana. 

Because of bad weather on April 21, the next test was made on April 22, with everything as usual. Unaided, the ape was given an opportunity toobtain the coveted reward, while I stood ready to obtain records of hisbehavior with my camera. He wasted no time, but piled the smaller box ontop of the larger one immediately, and obtained his reward. As soon asopportunity was offered, he repeated the performance. The same thinghappened on April 23 and several succeeding dates. 

Julius had got the idea, and the only further improvement possible wasin skill in manipulating the boxes. 

One of the curious performances which appeared during the imitativeperiod is pictured in figure 26, plate V, where the ape is seen liftingthe smaller box into the air. This he did three or four times one day, raising it toward the banana each time as though he expected thus toobtain the reward. As he did not go up with the box (according to hisexpectation?), he abandoned this method, and looking about, discoveredthe larger box in a distant corner. Thereupon, he promptly pulled theboxes to their proper position beneath the banana, stacked them, andobtained his food. 

After considerable skill had been acquired in the placing of the boxes, the one upon the other, the height of the banana above the floor wasincreased so that three boxes were necessary. Figure 25 of plate V showshim standing on three boxes and reaching upward, and figures 22, 27 and28 show various modes of handling the boxes and of reaching from them. He was not at all particular as to the stability of his perch, and oftenmounted the boxes when it seemed to the experimenter inevitable thatthey should topple over and precipitate him to the floor. Only once, however, during the several days of experimentation did he thus fall. 

Obviously important is the evident change in the animal's attention onApril 20. He watched with a keenness of interest which betokened adawning idea. Before he had succeeded in stacking the boxes, I hadwritten in my note-book, "He seemed much interested today, in my placingof the boxes. " Interesting, and important also, is the ease andefficiency with which he met the situation time after time, after thisfirst success. "Trial and error" had no obvious part in the developmentof the really essential features of the behavior. The ape had the ideaand upon it depended for guidance. 

Except for the fact that Julius was immature, probably under five yearsof age, it is likely that he would have stacked the boxes spontaneouslyinstead of by suggestion from the experimenter or imitatively. 

No unprejudiced psychologist would be likely to interpret the activitiesof the orang utan in the box-stacking experiment as other than imaginalor ideational. He went directly, and in the most business-like way frompoint to point, from method to method, trying in turn and more or lesspersistently or repeatedly, almost all of the possible ways of obtainingthe coveted food. The fact that he did not happen upon the only certainroad to success is surprising indeed in view of the many ineffectivemethods which he used. It seemed almost as though he avoided the easymethod. 

It is especially important, in connection with these results, to pointout the risk of misinterpretation of observations on the anthropoidapes. If they can imitate human activities as readily and effectively asJulius did in this particular experiment, we can never be sure of thespontaneity of their ideational behavior unless we definitely know thatthey have had no opportunity to see human beings perform similar acts. 

Of all the methods of eliciting ideational or allied forms of behaviorused in my study of the monkeys and ape, none yielded such illuminatingresults as the box stacking test, and although from the technicalstandpoint, it has many shortcomings, as a means to qualitative resultsit has proved invaluable. 

_Other Methods of Obtaining the Reward_

Some weeks later, I tried to discover how Julius would obtain the muchdesired banana when the boxes were absent. I placed in the large cage astick about six feet long and an old broom. When admitted, he lookedabout for the boxes, but not seeing them, picked up the broom andplacing it with the splints down, beneath the banana, he tried to climbit, but as it fell over with him, he abandoned this after a few trials, went to his cage, and picking up some old bags which he used at night ascovers, he dragged them out and placed them on the floor beneath thebanana. He next put the broom upon them and tried to climb up. Thisgeneral type of behavior persisted for several minutes, everythingwithin reach being used as were the bags, as a means of raising him inthe desired direction. Finally, he placed his feet on the broom wherethe handle joins the splints, seized the handle near the top with hishands, drew himself up as far as possible, and then launched himself inthe air and tried to seize the banana. On the third attempt hesucceeded. 

Later, he was given a plain stick about five feet long. Figure 32 ofplate VI shows him using this to obtain the banana in the mannerdescribed above. He would grasp it with one or both feet, usually one, ten to fifteen inches from the floor of the cage, meanwhile holding withhis hands near the top of the stick. He would then, with all hisstrength, draw himself up suddenly and jump toward the banana. Often hecame down rather hard on the cement floor, much to his disgust. 

Yet another method of obtaining the reward developed a day or two later. A light red-wood stick about five feet long and an inch in its otherdimensions was the only object in the cage which could possibly be ofuse in obtaining the banana. The aim of the experimenter was to discoverwhether Julius would use this as a club. 

Previously, in connection with the use of the boxes, he had taken up thesame stick two or three times and reached for the banana with it, but inno case had he struck at it or clearly tried to knock it from thestring, as did the child most readily and naturally. When provided withthis same stick, and it alone, as a means of obtaining the food, he hitupon the following interesting method. Placing one end of the stickbetween a wooden brace and the wire side of the cage, he climbed up to alevel with the banana as is shown in figure 33 of plate VI. Then holdingwith one hand and one foot to a timber of the cage and to the stick withhis other foot, he swung outward as far as possible and reached thebanana with his free hand. Having once succeeded by the method, he usedit whenever given an opportunity. It was impossible for him to make thereach without the use of the small stick, while with it he succeededfairly easily and regularly. 

_Box and Pole Experiment_

Following the box stacking test, Julius was given an opportunity toexhibit ideation in another type of experiment. This may be designatedthe box and pole test. The conditions are describable thus. A strongwooden box eighty-four inches long, by four inches wide, by four inchesdeep, with open ends, was built with one side hinged. Hasps and padlocksenabled the experimenter to lock this "lid" after food had been placedin the center of the box. This box could be placed in the center of thelarge cage and there fastened by means of cross bars. It is well shownin position in figure 29, plate V. Two poles each eight feet long andapproximately one and a half inches in their other dimensions were theonly additional materials in the experiment. 

On May 1, Julius was allowed to see the experimenter place a half bananain this box, close the lid, lock it in position, and securely fasten thebox by means of the cross bars. He was then given opportunity to try toget the banana. The two poles lay on opposite sides of the box and nearthe edges of the cage. Doctor Hamilton and the writer were in the cagewatching. Julius looked into the box through one end, and seeing thebanana, reached for it. He could not obtain it in this way, so he beganto bite at the box and to pull at it with all his strength. During thefifteen minutes allowed him, he worked at the box in a great variety ofways, fooling with the locks which had been attached to the hasps aswell as with the cross bars and continually reaching in at the one orthe other end. He was somewhat distracted by the presence of the twoobservers and attended rather unsatisfactorily to the task in hand. Notonce did he touch the poles, and it is doubtful whether he even noticedthem. He was not very hungry at this time, and after a few minutesactive work he virtually gave up trying to get the food. 

Two days later, on May 3, the box was once more placed in position, thistime with a half banana in the middle and a small piece of banana neareach open end. The two poles lay on the floor of the cage, each severalfeet distant from the box. Julius was eager for food. When released hewent immediately to the box, reached in and obtained a piece of bananafrom the end nearer the laboratory. He then looked in and saw the piecenear the middle of the box. His next move was to pick up the eight footpole and push it into the box, but before pushing it all the waythrough, he stopped and began to pull at the box in various ways. Shortly he returned to the pole and twice thrust it in as far as hecould reach. The first time, after thrusting it all the way through, hepulled it out and examined the end as though expecting the banana tocome out with it. After a third attempt he looked into the box, presumably seeing the banana, then turned a backward somersault, came tothe end of the cage, and looked at me. Had it been at all possible, hewould have taken me by the hand and led me to the box as a helper. Aftera few seconds, he returned to the pole, pried the lid of the box withit, then gnawed at the pole. For about five minutes he worked fairlyrapidly and steadily, using the poles, pulling, gnawing, and walkingabout. 

His next move was to go to the opposite end of the box, look in, takethe piece of banana which was near the opening, then pick up the secondpole, which had not previously been noticed, and after a number ofattempts, push it into and through the box, looking after it and thenpulling it out and looking into the box. Having done this he again cameto my end of the cage, and from there returned to try once more with thepole which he had first used. He pushed this pole all the way through, then walked to the other end of the box, looked in and reaching in, obtained the banana which had been pushed far enough along to be withinhis grasp. Figures 29, 30 and 31 of plate V show stages of this process. 

Julius had worked twenty-four minutes with relatively little lost timebefore succeeding. He had shown almost from the start the idea of usingthe pole as an instrument, and his sole difficulty was in making thepole serve the desired purpose. 

The experiment was rendered still more crucial on May 5 by the placingof the two poles upright in opposite corners of the large cage. For afew minutes after he entered the cage, Julius did not see them, and histime was spent pulling and gnawing at the box. Then he discovered one ofthe poles, seized it, and pushed it into the box. He tried four times, then went and got the other pole and pushed it into the opposite end ofthe box. Twice he did this, then he returned to the original pole, bringing the second one with him. He pushed it in beside the first, andas it happened, shoved the banana out of the opposite end of the box. But he did not see this, and only after several seconds when he happenedto walk to that end of the box did he discover the banana. The totaltime until success was fifteen minutes. 

Subsequently the ape became very expert in using the pole to obtain thebanana, and often only a minute or two sufficed for success. It was notpossible for him to direct the stick very accurately, for when he was insuch a position that he could look through the box, he could not workthe stick itself. It was, therefore, always a matter of chance whetherhe obtained the banana immediately or only after a number of trials. 

Although it is possible that the use of the poles in this experiment wasdue to observation of human activities, it seems probable in the lightof what we know of the natural behavior of the anthropoid apes thatJulius would have solved this problem independently of human influence. It was the expectation of the experimenter that the pole would be usedto push the banana through the box, but as a matter of fact the ape usedit, first of all, to pull the food toward him, thus indicating a naturaltendency which is important in connection with the statements just made. Subsequently he learned that the banana must be pushed through andobtained at the farther end of the box. I am not prepared to accept thesolution of this problem as satisfactory evidence of ideation, but I doknow that few observers could have watched the behavior of the orangutan without being convinced that he was acting ideationally. 

_Draw-in Experiment_

An interesting contrast with the box and pole test is furnished by whatmay be called the draw-in experiment. This was planned as a simple testof Julius's ability to use a stick to draw things into his cage frombeyond the wire side. A board was placed, as is shown in figure 34 ofplate VI, with sides to hold a banana, carrot, or some other bit offood, in position. In the actual test either a carrot or a banana wasplaced about two feet from the wire netting and a stick two feet longwas then put into the cage with the ape. 

When this situation was first presented to Julius, he looked at thebanana, reached for it, and failing, picked up a bag from the floor ofthe cage and tried to push it through the wire mesh toward the banana. He also used a bit of wire in the same way, but was unable thus to getthe food. As soon as a stick was placed in his cage, he grasped it andused it in a very definite, although unskillful, way to pull the bananatoward him. He was extremely eager and impatient, but neverthelesspersistent in his efforts, and within five minutes from the beginning ofthe first trial, he had succeeded in getting two pieces of banana, usingalways his left hand to manipulate the stick. This test was repeated anumber of times with similar results. He had from the first the abilityto use a stick in this way, and the only difficulty with the test as ameans of obtaining evidence of ideational behavior is that thepossibility of imitation of man cannot be certainly excluded. 

_Lock and Key Test_

By my assistant it was reported on May 5 that the orang utan had beenseen to place a splinter of wood in a padlock which was used on thecages and to work with it persistently. It looked very much likeimitation of the human act of using the key, and I therefore planned atest to ascertain whether Julius could readily and skillfully use a keyor could learn quickly to do so by watching me. 

The first test was made on May 15 with a heavy box whose hinged lid washeld securely in position by means of a hasp and a padlock. The key, which was not more than an inch in length, was fastened to a six inchpiece of wire so that Julius could not readily lose it. With the animalopposite me, I placed a piece of banana in the box, then closed the lidand snapped the padlock. I next handed Julius the key. He immediatelylaid it on the floor opposite him and began biting the box, rolling itaround, and occasionally biting also at the lock and pulling at it. During these activities he had pulled the box toward his cage. Now hesuddenly looked up to the position where the banana had been suspendedin the box experiment. Evidently the box had suggested to him thebanana. For thirty minutes he struggled with the box almostcontinuously, chewing persistently at the hinges, the hasp, or the lock. Then he took the key in his teeth and tried to push it into one of thehinges, then into the crack beneath the lid of the box. 

Subsequently I allowed him to see me use the key repeatedly, and as aresult, he came to use it himself now and then on the edge of the box, but he never succeeded in placing it in the lock, and the outcome of theexperiment was total failure on the part of the animal to unfasten thelock of his own initiative or to learn to use the key by watching me doso. I did not make any special attempt to teach him to use the key, butmerely gave him opportunity to imitate, and it is by no means impossiblethat he would have succeeded had the key been larger and had thesituation required less accurately coordinated movements. However, it isfair to say that the evidence of the idea of using the key in the lockwas unconvincing. My assistant's observation was, perhaps, misleading inso far as it suggested that idea. It may and probably was purely byaccident that the animal used the splinter on the padlock. 

2. Skirrl, _Pithecus irus_

_Box Stacking Experiment_

The monkey Skirrl was tested by means of the box stacking experimentmuch as Julius had been. On August 23, with a carrot suspended six feetfrom the floor of the large cage and three boxes in distant corners, theanimal was admitted and his behavior noted. 

The boxes, which were made of light, thin material, ranged in size fromone six inches in its several dimensions to one twenty inches long, thirteen inches wide, and eleven inches deep. Only by using at least twoof these boxes was it possible for the animal to reach the carrot. 

Immediately on admission to the cage, Skirrl began to gnaw at the boxes, trying with all his might to tear them to pieces. After some thirtyminutes of such effort, interrupted by wanderings about the cage andattempts to get at the other monkeys, he suddenly went to the largestbox of all, set it up on end almost directly under the carrot, mountedit, and looked up at the food. It was still beyond his reach and he madeno effort to get it, but instead, he reached from his perch on the bigbox for the next smaller box, which was approximately sixteen inches, byfourteen, by twelve. This he succeeded in pulling toward him, at thesame time raising it slightly from the floor, but his efforts caused thelarge box to topple over and he quit work. The experiment wasdiscontinued after a few minutes, the total period of observation havingbeen thirty-five minutes. 

Skirrl handled the boxes with ease and with evident pleasure andinterest. He also noticed the carrot at various times during theinterval, but his attention was fixed on it only for short periods. 

The test was continued on August 24 when, instead of a carrot, a halfbanana was used as bait. It was placed only five feet from the floor, and three boxes were as formerly placed in distant corners of the cage. When admitted, Skirrl looked at the banana, then pulled one of the boxestoward it, but instead of mounting, he went to the smallest box andbegan to gnaw it. Shortly, he mounted the middle sized box and looked uptoward the banana, but the box was not directly under the bait, and inany event, it would have been impossible for him to reach it. He nextwent to the largest box, gnawed it vigorously, turned it over severaltimes, and then abandoned it for the middle sized box, from which byskillful use of his teeth and hands, he quickly tore off one side. 

By this time, apparently without very definitely directed effort on thepart of the monkey, all three of the boxes were in the center of thecage and almost directly beneath the banana. Skirrl climbed up on thelargest box and made efforts to pull the middle sized one up on to it, the while looking at the banana every few seconds. He did not succeed ingetting the boxes properly placed, and after a time began moving themabout restlessly. 

His behavior plainly indicated that hunger was not his chief motive. Hewas more interested in playing with things or in working with them thanin eating, and the satisfaction of tearing a box to pieces seemed evengreater than that of food. It is especially noteworthy that when Skirrlattempts to dismember a box, instead of starting at random, he searchescarefully for a favorable starting point, a place where a board isslightly loosened or where a slight crack or hole enables him to inserthis hand or use his teeth effectively. Many times during this experimenthe was observed to examine the boxes on all sides in search of some weakpoint. If no such weak point were found, he shortly left the box; but ifhe did find a favorable spot, he usually succeeded, before he gave upthe attempt, in doing considerable damage to the box. 

Following the behavior described above, Skirrl returned to the middlesized box, placed it on end under the banana, mounted, and looked upwardat the bait, but as it was a few inches beyond his reach, he made noattempt to get it, but instead, after a few seconds, went to thesmallest box, and finding a weak point, began to tear it to pieces. 

Later he rolled what was left of the smallest box close to the other twoboxes, nearly under the banana, and the remainder of his time was spentgnawing at the boxes and playing with pieces which he had succeeded intearing from them. During the remainder of the thirty minute interval ofobservation, no further attention was given the bait. 

Again, on August 25, the test was tried, but this time with boxes whoseedges had been bound with tin so that it was impossible for the monkeyto destroy them. He spent several minutes searching for a starting pointon the middle sized box, but finding none, he dragged it under thebanana, looked up, mounted the box, but, as previously, did not reachfor the bait because it was beyond his reach. He then played with theboxes for several minutes. Finally he worked the two smaller boxes to aposition directly under the banana, put the middle sized one on end, mounted it, and looked at the bait, but again abandoned the attemptwithout reaching. 

During the thirty minutes of observation he made no definite effort toplace one box upon another. Three times he mounted one or another of theboxes when it was under the banana or nearly so, but in no case was itpossible for him to reach the bait. 

From the above description of this monkey's behavior, it seems fairlycertain that with sufficient opportunity, under strong hunger, he wouldultimately succeed in obtaining the bait by the use of two or moreboxes. For his somewhat abortive and never long continued efforts todrag two boxes together or to place the one upon the other clearlyenough indicate a tendency which would ultimately yield success. Thepossibility of imitation is not excluded, for Skirrl had opportunitiesto see Julius and the experimenter handle the boxes. 

Because of the other work which seemed more important at the time, thisexperiment was not continued further. The results obtained suggest thedesirability of testing thoroughly the ability of monkeys to use objectsas only the anthropoid apes and man have heretofore been thought capableof using them. 

_Box and Pole Experiment_

Skirrl was first tested with the box and pole experiment on August 12. As in the case of Julius, a half banana was placed in the middle of thelong box and the attention of the monkey was attracted to the bait bysmall pieces of carrot placed near each open end. Two poles were placednear the box on the floor of the cage. When admitted to the cage Skirrlwent almost directly to the ends of the box, took the pieces of carrotwhich were in sight, but apparently failed to perceive the bait in themiddle of the box. For a while he played with the locks on the box, shoved it about, and amused himself with it, showing no interest inobtaining the food. Later he looked through the box and saw the banana. He then dragged the box about, apparently trying to get it into hiscage, but he gave no attention to the poles nor did he make any evidenteffort to obtain the banana which was easily visible in the center ofthe box. The period of observation was only twelve minutes. 

On August 24 this experiment was repeated with an important modificationof the apparatus in that the wooden lid of the long box had beenreplaced by a wire cover through which the animal could see the bait. Two poles were as formerly on the floor of the cage, not far from thebox. Skirrl almost immediately noticed the banana and tried to get it bygnawing at the box. He did not once reach in at the ends of the box, buthe did handle the poles, throwing them about and pounding with them. There was not the slightest attempt to use them in obtaining the bait. 

This experiment was later repeated three times at intervals of a numberof days, but in no case did Skirrl show any tendency to use the poles asmeans of obtaining the food. 

_Draw-in Experiment_

This also was arranged in the same manner as for Julius, and on each offive days Skirrl was allowed at least thirty minutes to work for thebait. Either a banana or a carrot was each day placed on the board wellbeyond his reach, and one or two, usually two, small sticks were putinto his cage. Not once during the several periods of observation didSkirrl make any attempt to use a stick or any other object as a means ofdrawing the food to him. Instead, he reached persistently with his arm, pulled and gnawed at the wires which were in his way, and occasionallypicked up and gnawed or pounded with the sticks in the cage. Hisattention every now and then would come back to the food, but it tendedto fluctuate rather rapidly, and in the regular period of observation, thirty minutes, it is unlikely that he attended to the bait itself foras much as five minutes. In this respect as well as many others, Skirrl's behavior contrasts sharply with that of the orang utan. 

The results of this experiment indicate the lack in the monkey of anytendency or ability, apart from training, to use objects as means ofobtaining food. Ways of using objects as tools which apparently areperfectly natural to the anthropoid apes and to man are rarely employedby the lower primates. 

_Hammer and Nail Test_

One day I happened to observe Skirrl playing with a staple in his cage. He had found it on the floor where it had fallen and was intentlyprodding himself with the sharp points, apparently enjoying the unusualsensations which he got from sticking the staple into the skin invarious portions of his body, and especially into the prepuce. 

A few days later I saw him playing in similar fashion with a nail whichhe had found, and still later he was seen to be using a stick to poundthe nail with. This suggested to me the hammer and nail test. 

A heavy spike was driven into an old hammer to serve as anindestructible handle. This hammer, along with a number of large wirenails and a piece of redwood board, was then placed in the monkey'scage. Skirrl immediately took up the hammer, grasping the middle of thehandle with his left hand, and with his right hand taking up a nail. Hethen sat down on the board, examined the nail, placed the pointed end onthe board, and with well directed strokes by the use of the head of thehammer drove the nail into the board for the distance of at least aninch. He then tried to pull it out, but was forced to knock it severaltimes with the hammer before he could do so. 

This performance, during the next few minutes, was repeated severaltimes with variations. Often the side of the hammer was used instead ofthe head, and occasionally, as is shown in figure 8 of plate II, heseized the hammer well up toward the juncture of the same with thespike. This figure does justice to the performance. At the moment thepicture was taken, Skirrl's attention had been attracted by a monkey inan adjoining cage, and he had momentarily looked up from his task, thewhile holding nail and hammer perfectly still. 

This test was repeated on various days, and almost uniformly Skirrlshowed intense interest in hammer and nails and used them more or lesspersistently in the manner described. Occasionally, apparently for thesake of variety, he would put the blunt end of the nail on the board andhammer on the point. Again, he would try persistently to drive the nailinto the cement floor, and once by accident, when hammer and nails wereleft in his cage over night, he succeeded in making several holes in thebottom of his sheet iron water pan. There was no doubting the keensatisfaction which the animal took in this form of activity. 

It is impossible to say that the behavior was not imitative of man, forSkirrl, along with all of the other monkeys, had had abundantopportunity to see carpenters working. But this much can be said againstthe idea of imitation, --no one of the other animals, not excepting theorang utan, showed any interest whatever in hammer and nails. Occasionally they would be played with momentarily or pushed about, butSobke, Jimmie, Gertie, Julius, although given several opportunities toexhibit any ability which they might have to drive nails, made not theleast attempt to do so. Evidently we must either conclude that Skirrlhad a peculiarly strong imitative tendency in this direction, orinstead, a pronounced disposition or instinct for the use of objects astools. It would seem fair to speak of it as an instinct for mechanicalactivity. 

Under this same heading may be described Skirrl's reactions to suchobjects as a handsaw, a padlock, and a water faucet. The saw was givento him in order to test his ability to use it in human fashion, for ifhe could so expertly imitate the carpenter driving nails, it seemslikely that he might also imitate the use of the saw. 

As a matter of fact, he showed no tendency to use the saw as we do. Instead, he persistently played with it in various ways, at first usingit as a sort of plane to scrape with, later often rubbing the teeth overa board so that they cut fairly well, but never as effectively as in thehands of a man. After two or three days' practice with the saw, Skirrlhit upon a method which is, as I understand, used by man in certaincountries, namely, that of placing the saw with the teeth up, holding itrigid, and then rubbing the object which is to be sawed over it. ThisSkirrl succeeded in doing very skillfully, for he would sit down on thefloor of the cage, grip with both feet the handle of the saw, with theteeth directed upward, then holding either end in his hands, he wouldrepeatedly rub a stick over the teeth. In this way, of course, he couldmake the saw cut fairly well. But still more to his liking was the useof a spike instead of a stick as an object to rub over the teeth, forwith this he was able to make a noise that would have satisfied even asmall boy. 

Further light is shed on the force of the tendency to imitate man by thesaw test. After Skirrl had been given an opportunity to show what hecould do with the tool spontaneously, I demonstrated to him the approvedhuman way of sawing. Often he would watch my performance intently asthough fascinated by the sound and motion, but when given the tool heinvariably followed his own methods. Although I repeated this test ofimitation several times on three different days, the results were whollynegative. 

_Other Activities_

One day as Skirrl was being returned to his own cage by way of thelarger cage, he picked up an unfastened padlock and carried it into thecage with him. For more than an hour he amused himself almost withoutinterruption by playing with this lock. The things which he did with itduring that time would require pages to describe. His interest in it wasvery similar to that which he had exhibited in hammer and nails, saw, and indeed any objects which he could play with. The lock was pounded invarious ways, bitten, poked with nails, hooked into the wires of thecage, used to pull on, pounded with a stick, used to hammer on the floorof the cage with, and in fine, manipulated in quite as great a varietyof ways as a human being could have discovered. Finally it was hooked tothe side of the cage and snapped shut, and as Skirrl was unable todislodge it from this position, he shortly gave up playing with it. 

At the end of the large cage and just outside the wire netting was afaucet to which a hose was usually attached. The valve could be openedby turning a wheel-shaped hand piece. Both Skirrl and Julius learned toturn this wheel in order to get water to play with, but usually theformer's strength was not sufficient to turn on the water. The lattercould do it readily. The indications are that both animals profited byseeing human beings turn on the water. This unquestionably attractedtheir attention to the faucet, and probably by playing with it theyaccidentally happened upon the proper movement. At any rate, Skirrl'sbehavior was significant in this connection, for he would pick up thehose to see if water were flowing, and if it were not, he would throw itdown, go directly to the faucet, and try to turn the wheel. Theassociation of the wheel with the desired flow of water was thereforedefinitely established. Shall we describe the act as ideational? Itseems the natural thing to do. 

3. Sobke, _Pithecus rhesus_

_Box Stacking Experiment_

For this test, in the case of Sobke, three light boxes made of redwoodabout one-third of an inch thick were used. The smallest, box 1, was sixinches in each direction, the next larger, box 2, was twelve inches, andthe third, box 3, eighteen inches. As in the case of the other animals, bait, either banana or carrot, was suspended from the middle of the roofof the large cage at such distance from the floor as to be reached bythe animal only by the use of the boxes. 

The first observations on Sobke were made on June 14. The three boxeshad been placed in the form of a pyramid directly under the banana, which hung about eighteen inches above the uppermost box. Sobke'sattention while in his cage had been attracted to the bait by seeing mefastening it in position, but when admitted to the large cage, he simplyglanced at it and then wandered about the cage, picking up bits of foodand struggling to get at the other monkeys. This he did for about fiveminutes. He then went to the boxes, placed his hands on top of thebottom one, but did not climb up on it. A few minutes later he returnedto the box again, climbed up, and readily reached the food, which he atewhile resting on boxes 1 and 2. 

I now replaced the bait and gave the monkey a second chance to obtainit. Almost immediately he climbed up as far as the second box, butalthough he could reach the banana only from the uppermost box, hedeliberately shoved it off to the ground and sat down upon box 2. As hewas unable to obtain the banana from this, he soon began to gnaw andpull at it, and as he was succeeding all too well in his efforts to tearthe box to pieces, he had to be returned to his cage. 

The most important features of his behavior were, first, his stealthyand indirect manner, and second, his failure to use other means ofobtaining the bait than that supplied by the observer. Instead oflooking straight at the experimenter, or at the object which he wishedto obtain, he apparently looked and attended elsewhere. For this reasonit was often difficult to decide whether or not he had noticed the baitor the boxes. Finally I was led to conclude that he usually knew exactlywhat was going on and had in his furtive way noted all of the essentialfeatures of the situation, and that his manner was extremely indicativeof his mental attitude of limited trust. Both Julius and Skirrl went tothe opposite extreme in the matter of directness, or as we should say inhuman relations, frankness. They would look the experimenter directly inthe eye, and they usually gazed intently at anything, such for exampleas the bait, that interested them. Sobke, even when very hungry, insteadof going directly toward the bait, and trying to obtain it, usually didvarious other things as though pretending that he had no interest infood. 

On the following day, June 15, the three boxes were again placed nearlyunder the banana, but this time the two smaller boxes, numbers 1 and 2, were pushed to the extreme end of the lower box and so far from the baitthat it could not be reached from box 1. It was necessary then for theanimal to push boxes 1 and 2 along on box 3 until they were nearer thebait. 

Sobke, when admitted to the cage, evidently noticed the banana, but asformerly, he made no immediate effort to obtain it. After wandering insearch of food and quarreling with the other monkeys for severalminutes, he went to the boxes, pushed the topmost one, number 1, off onto the floor, and then carried it into his cage where he quickly toreone side off. He next returned to the large cage, climbed up on box 2, and he was able, by jumping, to reach and obtain the banana. 

As Sobke was very good at jumping, his new method rendered the boxstacking experiment of uncertain value, since it was next to impossibleso to arrange the spatial relations of bait and boxes that he should beneither discouraged by too great a distance nor encouraged to jump bytoo small a distance. Evidently it would be more satisfactory tosimplify the conditions by trying to discover, first of all, whether hewould use a single box as a means of reaching the reward. 

In pursuance of this idea, I suspended a piece of bread five feet fromthe floor of the cage, and a few feet to one side of it, I placed a boxfrom which it could be reached, or at least easily seized by jumping. Sobke shortly walked to a point beneath the bait and leaping into theair, seized it. 

I then replaced the bait, raising it to a height of five feet ten inchesfrom the floor of the cage. When I had retired, Sobke placed himself inthe proper position beneath, looked up at it, but went away withoutjumping for it. During the remaining ten minutes of observation, he paidno further attention to the bait, having satisfied himself evidentlythat it was beyond his reach. 

My use of this test was concluded on June 16 when once more I suspendeda piece of bread six feet from the floor and placed a few feet to oneside the eighteen inch box, number 3, from which had the monkey pushedit to a point directly under the bread, he could have obtained the foodeasily. Sobke noticed the food promptly, and from time to time as hewandered about, he glanced at it out of the corner of his eye, but notonce did he sit down and look at it steadily and directly as Julius andSkirrl might have done. 

In the first twenty minutes of observation the monkey made no attempteither to use the box or to reach the food by jumping. I then placed thebox directly under the bait, and scarcely had I withdrawn from the cagebefore Sobke climbed up on it and looked toward the food. He could notreach it without jumping, and he made no effort to get it. I had left asecond box in the cage, --one which I had been using as a seat. Sobke nowwent to this box, placed his hands on it, looked toward the bait, andthen went to a distant part of the cage. No further indications wereobtained during the remainder of the period of observation of interestin the boxes as possible means of obtaining the desired food. 

It is of course obvious that this experiment was not long enoughcontinued to justify the conclusion that either Sobke or Skirrl couldnot use the boxes or even learn to place one box upon another in orderto obtain the bait. The experiment, like several others which are beingdescribed briefly, was used to supplement the multiple-choiceexperiment, and the experimenter's chief interest was to discover thenumber and variety of methods which would be used by the animal inthe first few presentations of a situation. It is practically certainthat both of these monkeys would have succeeded ultimately in solvingthe problem of obtaining the food had they been left in the cage with anumber of boxes, for Skirrl very early indicated interest in moving theboxes about, and Sobke showed a tendency in that direction which perhapswas inhibited partially by his distrust of the experimenter. 

_Draw-in Experiment_

For Sobke, as for Julius and Skirrl, the draw-in test was made byputting food on a shelf outside the cage, beyond the reach of theanimal, and placing in the cage with the animal one or two sticks longenough to be used for drawing in the bait. 

Sobke was first given this test on July 24. He tried persistently toreach the banana with his hand, seized the box which supported the bait, shook it, picked up one or other of the sticks, and chewed at itrepeatedly, but not once did he make any move to use a stick to draw thefood toward him. 

This experiment was repeated on July 27, 29, 30 and 31, a period ofthirty minutes being allowed on each day for observation. At no time didSobke show any inclination to use either a stick or any other object asa means of reaching the bait. Instead, he confined himself strictly tothe use of hands and teeth. 

This test makes it fairly certain that Sobke had no natural tendency touse objects as tools. In so far as he attended to things about the cageor laboratory, it seemed to be rather to play with them in a general waythan to use them ideationally or otherwise for definite purposes. 

The definitely negative result of the draw-in experiment renderedneedless prolonged observation with the box and pole test, whose resultsare now to be presented. 

_Box and Pole Experiment_

The eighty-four inch box, previously used for a similar test withJulius, was presented to Sobke on August 24, the wooden cover havingbeen replaced by a wire one so that the monkey could readily see thebait in the middle of the box. Sobke, when admitted to the large cage, went directly to the box and at once discovered the banana which wasmidway between the ends. He evidently desired it. Shortly, he went toone end of the box and looked in. This he repeated later. He also shookthe box and tried to pull it about and tear it with his teeth, but tothe two poles lying nearby on the floor of the cage he gave not theslightest attention during a thirty minute period of observation. 

The experiment was not repeated because of more important work. 

_Other Activities_

In more respects than I have taken time to enumerate in the abovedescriptions of behavior, the relations of Sobke to objects differedfrom those of Skirrl, and still more from those of Julius. Hammer, nails, saw, stones, sticks, locks, and various other objects receivedrelatively little attention from Sobke unless they happened to come inhis way; then they were usually pushed aside with but scant notice. Rarely he would carry something to the shelf of his cage with him, butas a rule only to lay it down and attend to something else. Skirrl, onthe contrary, attended persistently to anything new in the shape of amovable object. He was extremely partial to objects which could bemanipulated by him in various ways, and especially to any thing withwhich he could make a noise. His interest in hammer and nails, saw, locks, etc. , seemed never to wane. I have seen him play for an houralmost uninterruptedly with a hammer and a nail, or even with a bigspike which he could use to pry about his cage. In the absence ofanything more interesting, even a staple or a small nail might receivehis undivided attention for minutes at a time. How important is thespecies difference in this connection, I have no means to judge, but ifwe may not consider these different modes of behavior characteristic of_P. Rhesus_ as contrasted with _P. Irus_, we must conclude thatremarkable individual differences exist among monkeys, for whereasSkirrl is by nature a mechanical genius, Sobke has apparently no suchdisposition. I can imagine no more fascinating task than the carefulanalytical study of the temperaments of these two animals. Skirrl'sbehavior has importantly modified my conception of genius. 

V

MISCELLANEOUS OBSERVATIONS

1. _Right- and left-handedness_

Several years ago Doctor Hamilton reported to me observations which hehad made on preference for the right or left paw in dogs. He has not, Ibelieve, published an account of his work. Subsequently, Franz observeda similar preference in monkeys which, according to his report, exhibitmarked tendency to be right-handed, left-handed, or ambidextrous. 

My own observations, although they are wholly incidental to my otherwork, seem worthy of description at this point. I noted, first of all, that the orang utan Julius tended to use his left hand. He by no meanslimited himself to this, but in difficult situations he almostinvariably reached for food or manipulated objects in connection withfood getting with the left hand. Figures 23 and 24 of plate V, show himreaching for a banana with the left hand. Likewise, figure 34 exhibitsthe use of the left hand in the draw-in experiment. 

So marked was Julius's preference for his left hand that I becameinterested in observing similar phenomena in the monkeys. Skirrl, whendriving nails, held the hammer with his left hand and the nail with hisright hand. The fact that he never was observed to reverse the use ofthe hands is surprising, for other observations indicate that hepreferred the right hand for certain acts. 

Stimulated by the obvious left-handedness, in certain connections, ofJulius and Skirrl, I tested the preference of several of the monkeys inthe following simple way. Standing outside the cage I would hold out apeanut to a hungry animal, keeping it so far from the cage that themonkey could barely reach it with its fingers. I noted the hand whichwas used to grasp the food. Next I varied the procedure by placing thepeanut on a board in order to make sure that I was not definitelydirecting the animal's attention. 

With Sobke the following results were obtained. In forty trials given ontwo different days, he reached for and obtained the food each time withhis left hand. Only by holding the bait well toward the right side ofhis body was it possible to induce him to use the right hand. So far asmay be judged from these observations and from others in connection withthe experiments, this animal is definitely left-handed. 

With Skirrl the results are strikingly different. As stated above, heused the hammer consistently with his left hand, but in twenty attemptsto obtain food by reaching, he used his right hand seventeen times andhis left only three times. It was quite as difficult to induce him touse his left hand for this purpose as it was to induce Sobke to use hisright. We must therefore conclude that Skirrl is right-handed inconnection with certain movements and left-handed in others. 

The monkey named Gertie in the reaching experiment consistently used herleft hand, never once using the right. 

Jimmie, so far as it was possible to make tests with him, also used hisleft hand, but it should be said that the results are unsatisfactorybecause he was at the time extremely pugnacious and paid attention tothe experimenter rather than to the food. 

Scotty, in the first series of ten trials, used his right hand eighttimes, his left twice. In the second series, given the following day, heused the right hand three times and the left seven times. From this weshould have to infer that he is ambidextrous. 

A female _rhesus_ monkey which had been brought to the laboratory only afew days previously showed a preference for the right hand by the use ofit fourteen times to six. 

In connection with these data which are, I should repeat, too scanty tobe of any considerable value, I wish to describe my own experience. Although naturally left-handed, I am by training right-handed to theextent of having been able to use my hands in writing and in variousother activities equally well at the age of twelve. I am at presentambidextrous in that there are many things which I do with equalreadiness and skill with either hand. Delicate, exact, and finelycoordinated movements, such as those of writing and using surgicalinstruments, I perform always with my left hand while grosser movementsinvolving the whole hand or arm, I am rather likely to perform with myright hand. 

It seems not improbable in the light of my own experience that we shallfind some specialization among the lower animals with respect topreference for right and left hand or arm. I should not be at allsurprised to discover that it is the rule for animals to possess or todevelop readily definite preference for one hand in connection with agiven act of skill and to have quite as definite a preference for theother hand in connection with a radically different kind of act. 

2. _Instinct and emotion_

Of the many presumably instinctive modes of behavior which wereobserved, only those which have to do with social relations seemespecially worth reporting. From among them I shall select fordescription a few which have already been referred to in connection withthe experimental observations. 

_Maternal Instinct_

Aspects of the maternal instinct I had opportunity to observe in Gertie, who on February 27 gave birth to a male infant, I present below thesubstance of a previously published note on her behavior (Yerkes, 1915). 

"On February 27 one of the monkeys of our collection gave birth, in thecages at Montecito, to a male infant. The mother is a _Macacuscynomolgus rhesus_ (_P. Irus rhesus_) who has been described by Hamilton(1914, p. 298) as 'Monkey 9, Gertie, _M. Cynomolgus rhesus_ (_P. Irusrhesus_). Age, 3 years 2 months. (She is now, May 1, 1915, 4 years and 6months. ) Daughter of monkeys 3 and 10. First pregnancy began September, 1913. ' The result of this pregnancy was, I am informed, a still-birth. 

"The second pregnancy, which shall now especially concern us, resultedlikewise in a still-birth. Parturition occurred Saturday night, and thewriter first observed the behavior of the mother the following Mondaymorning. In the meantime the laboratory attendant had obtained the dataupon which I base the above statements. 

"At the time of parturition Gertie was in a 6 by 6 by 12 foot out-doorcage containing a small shelter box, with an exceptionally quiet andgentle male (not the father of the infant) who is designated inHamilton's paper as Monkey 28, Scotty. 

"My notes record the following exceptionally interesting and geneticallyimportant behavior. On March 1, when I approached her cage, Gertie wassitting on the floor with the infant held in one hand while she fingeredits eyelids and eyes with the other. Scotty sat close beside herwatching intently. When disturbed by me the mother carried her infant toa shelf at the top of the cage. Repeatedly attempts were made to removethe dead baby, but they were futile because Gertie either held it in herhands or sat close beside it ready to seize it at the slightestdisturbance. 

"Especially noteworthy on this, the second day after the birth of theinfant, are the male's, as well as the female's, keen interest in thebody and their frequent examinations of the eyes, as if in attempts toopen them. Often, also, the mother searched the body for fleas. 

"Observations were made from day to day, and each day opportunity wassought to remove the body without seriously frightening or exciting thefemale. No such opportunity came, and during the second week the corpseso far decomposed that, with constant handling and licking by theadults, it rapidly wore away. By the third week there remained only theshriveled skin covering a few fragments of bone, and the open skull fromthe cavity of which the brain had been removed. This the mother neverlost sight of: even when eating she either held it in one hand or foot, or laid it beside her within easy reach. 

"Gradually this remnant became still further reduced until on March 31there existed only a strip of dry skin about four inches long with atail-like appendage of nearly the same length. 

"The male, Scotty, on this date was removed to another cage. Gertie madea great fuss, jumping about excitedly and uttering plaintive cries whenshe discovered that her mate was gone. Whenever I approached her cageshe scurried into the shelter box and stayed there while I was near. This behavior I never before had observed. It continued for two days. OnApril 2, it was noted that she had lost her recently acquired shynessand she no longer made any attempts to avoid me. As usual, on this date, she was carrying the remnant about with her. 

"The following day, April 3, Gertie was lured from her cage to a largeadjoining compartment for certain experimental observations. After shehad been returned to her own cage the remnant was noticed on the floorof the large cage. I picked it up. Gertie evidently noticed my act; foralthough at a distance of at least ten feet from me, she made a sharpoutcry and sprang to the side of the cage nearest me. I held the pieceof skin (it looked more like a bit of rat skin than the remains of amonkey) out to her and she immediately seized it and rushed with it tothe shelf at the top of the cage. 

"Two days later the remnant was missing, and careful search failed todiscover it in the cage. It is probable that Gertie had carelessly leftit lying on the floor whence it was washed out when the cages werecleaned. On this date Gertie seemed quieter than for weeks previously. 

"Thus it appears that during a period of five weeks the instinct toprotect her offspring impelled this monkey to carry its graduallyvanishing remains about with her and to watch over them so assiduouslythat it was utterly impossible to take them from her except by force. 

"After reading this note in manuscript, Doctor Hamilton informed me thatGertie had behaved toward her first still-birth as toward her second. And, further, that Grace, a baboon, also carried a still-birth about forweeks. 

"I am now heartily glad that my early efforts to remove the corpse werefutile, for this record of the persistence of maternal behavior seems tome of very unusual interest to the genetic psychologist. "

_Fear_

In connection with the multiple-choice experiments Skirrl exhibited whatseemed to be instinctive fear as a result of his unfortunate experiencewith nails in the floor of box 1. He seemingly referred his misadventureto some unseen enemy under the floor, and this in spite of the fact thathe was given abundant opportunity to examine the floor of the box, butnot until after the dangerous nails had been clinched. His longcontinued avoidance of the experiment boxes and his still morepersistent hesitancy in entering them, coupled with his almost ludicrousefforts to see beneath the floor through the holes cut for the stapleson the doors, gave me the impression of superstitious fear of theunseen. As I watched and recorded his behavior day after day during theperiod of most pronounced fear, I could not avoid the thought that theinstinctive fear of snakes had something to do with his peculiaractions, and although I have never studied either the natural or theacquired responses of monkeys to snakes, I suspect that lacking suchinstinctive equipment, Skirrl would have behaved differently as a resultof the pricks which he received from the nails. It is needless toredescribe his acquired fear of whiteness as it manifested itself in thefreshly painted apparatus. Accompanying these instructive modes ofresponse and their emotions are suggestions of peculiarly interestingproblems as well as of modes of attacking them. As a matter of fact, Skirrl's fear-reactions did much to alter my conception of theconstitution of his mind. I should not have been surprised by thefeatures of behavior exhibited, but I was by no means prepared for theirpersistence, and for the highly emotional attitude toward the particularsituation. Only an organism of complexly constituted nervous system andfairly highly developed affective life could be expected to respond asdid this monkey. As has been suggested above, I find the appeal toinstinct, modified by experience, a natural mode of accounting for theunexpected features of Skirrl's behavior. 

_Sympathy_

The instinctive playfulness of the young monkey Tiny contrasted moststrikingly with the more serious, if not more sedate, modes of behaviorof the older individuals. 

During the greater part of my period of observation Tiny was cage-mateof Scotty, the most calm and apparently lazy of all the monkeys. Tinydelighted in teasing Scotty, and her varied modes of mildly tormentinghim and of stirring him to pursuit or to retaliation were as interestingas they were amusing. Her most common trick was to steal up behind himand pull the hair of his back, or seize his tail with her hands orteeth. Often when he was asleep she would suddenly run to him, give asudden jerk at a handful of hairs, and leap away. He was surprisinglypatient, and I never saw him treat her roughly in retaliation. 

Another of Tiny's favorite forms of amusement was that of trying to stirup the other monkeys to attacks on one another. She very cleverly didthis by pretending that she herself was being attacked. The instant theolder animals began to show hostility toward one another she would leapout of the way and watch the disturbance with evident satisfaction. Itwas this mode of behavior in the little animal which ultimately providedopportunity for the observations which I wish now to report asindicative of sympathetic, possibly I may say altruistic, emotions. 

Tiny was confined with Scotty in a cage adjoining the one in whichJimmie and Gertie were being kept. The cages were separated by wirenetting of half-inch mesh. 

One morning as I was watching the behavior of the animals in the severalcages, I noticed Tiny dressing with her teeth a wounded finger. It hadevidently been bitten by one of the other animals, in all probabilityeither by Jimmie or Gertie. Tiny was trimming away the loose bits ofskin very neatly and cleansing the wound. After working at this task fora few minutes, she quickly climbed up to the shelf near the top of hercage, and by rushing to the partition wire between the two cages, shelured Gertie to an attempted attack on her. Gertie sprang up to thepartition, placed her hands on it, with the fingers projecting throughthe meshes, and attempted to seize Tiny's fingers with her teeth. Butthe latter was too quick for her, and withdrawing her hands, like aflash seized in her teeth the middle finger of Gertie's left hand. Shethen bit it severely and with all her might, at the same time pullingand twisting violently, often placing the entire weight of her body onthe finger. Her sharp teeth cut to the bone, and it was impossible forthe larger and stronger monkey to tear away. For several seconds thiscontinued, then Gertie succeeded in escaping, whereupon she at onceretreated to the opposite end of her shelf and proceeded to attend toher injured finger. She cried, wrung her hands, and from time to timeplaced the finger in her mouth as though in an effort to relieve thepain. By this time Jimmie's attention had been attracted by thedisturbance and he rushed up to the shelf, and facing Gertie, watchedher intently for a few seconds. The look of puzzled concern on his facewas most amusing. Apparently he felt dimly that something in which heshould have intelligent interest was going on, but was unable wholly tounderstand the situation. After watching Gertie for a time and trying todiscover what she was doing, which was rendered difficult by hertendency to turn away from him, in order to shield her injured finger, he rushed over to the wire partition and made strenuous efforts to seizeTiny with his hands and teeth. But although she continued close to thepartition and often crowded against it with face and hands flattened onthe wires, he was not able to get hold of her, and after a few vainattempts he returned to his mate, and again with evident solicitousnessand the most troubled expression, watched her wringing her hands andchewing or sucking at her injured finger. Shortly he again returned tothe partition and renewed his attempts to seize the young monkey. Thushe went back and forth from one place of interest to the other severaltimes, but being unable to achieve anything at either point, he finallygave up and returned to his breakfast on the floor of the cage. 

I report this incident fully because the behavior of Jimmie was inmarked contrast with the usual behavior of the monkeys. Selfishnessseemed everywhere dominant, while clear indications of sympatheticemotions were rare indeed. The above is undoubtedly the best evidence ofanything altruistic that I obtained. 

It is possible that Tiny's action was retaliatory, but although it ispractically certain that either Gertie or Jimmie inflicted the wound onher finger, I of course cannot be sure that the spirit of revengestirred her to punish Gertie so severely. Jimmie's part in the wholeaffair is, however, perfectly intelligible from our human point of view, and there seems no reason to doubt that he did experience something likea feeling of sympathy with his mate, coupled with a feeling ofresentment or anger against Tiny. 

VI

HISTORICAL AND CRITICAL DISCUSSION OF IDEATIONAL BEHAVIOR IN MONKEYS ANDAPES

It is my purpose in this section to indicate the relations of my work onmonkeys and apes to that of other investigators. Although throughout thereport I have used freely the psychological terms idea and ideation, ithas been my aim to describe the behavior of my animals rather than tointerpret it or speculate concerning its accompaniments. Certain acts Ihave designated as ideational simply because they seemed to exhibit theessential features of what we call ideational behavior in man. Furtherstudy may, and probably will, modify my opinion concerning this matter. It is of prime importance to analyze ideational behavior so that it maybe accurately described and satisfactorily defined in terms of itsdistinguishing characteristics. I had hoped to be able to present atentative analysis in this report, but the results of my efforts are sounsatisfactory that I do not feel justified in publishing them. 

The terms idea and ideation have been used to designate contents ofconsciousness which are primarily representative. Nowhere have Iattempted to indicate different types or grades of ideational behaviorand nowhere have I found it necessary to emphasize differences betweenimage and idea. In general, the acts which I have called ideational havebeen highly adaptive, and the learning processes in connection withwhich they have appeared have differed strikingly from those of theselective sort in their abruptness of appearance. 

Extremely interesting and valuable definitions of ideation anddiscussions of the characteristics of different sorts of ideas in thelight of original observations on monkeys have been presented byThorndike (1901, pp. 1, 2; 1911, p. 174); Kinnaman (1902, p. 200); andHobhouse (1915, p. 270). As these authors have contributed importantlyto our knowledge of the behavior of monkeys, their discussions of themeaning of terms are especially valuable. Serviceable definitions are tobe found, also, in Romanes (1900), Morgan (1906), Washburn (1908), andHolmes (1911). 

_Evidences of Ideation in Monkeys_

Aside from anecdotal and traveller's notes on the behavior of monkeysand apes we have only a scanty literature. In fact, the really excellentarticles on the behavior and mental life of these animals may be countedon one's fingers; and not more than half of these are experimentalstudies. I shall, in this brief historical sketch, neglect entirely theanecdotal literature, since my own work is primarily experimental, andsince its results should naturally be compared with those of otherexperimenters. 

Thorndike (1901), the American pioneer in the application of theexperimental method to the study of mind in animals, published the firstnotable paper on the psychology of monkeys. His results force theconclusion that "free ideas" seldom appear in the monkey mind and have arelatively small part in behavior. That the species of Cebus which heobserved exhibits various forms of ideation he is willing to admit. Buthe insists that it is of surprisingly little importance in comparisonwith what the general behavior of monkeys as known in captivity and asdescribed by the anecdotal writers have led us to expect. It isimportant to note, however, that Thorndike's observations were limitedto Cebus monkeys which, as contrasted with various old world types, arenow considered of relatively low intelligence. 

In many respects the most thoroughgoing and workmanlike experimentalstudy of monkeys is that of Kinnaman (1902), who has reported on thestudy of various forms of response in _P. Rhesus_. He presents valuabledata concerning the learning processes, sensory discrimination, reactionto number, and to tests of imitation. His results indicate a higherlevel of intelligence than that discovered by Thorndike, but this isalmost certainly due to difference in the species observed. Kinnamangoes so far as to say "We have found evidence, also, of general notionsand reasoning, both of low order" (p. 211). 

The contribution of Hobhouse (1915) to our knowledge of the mental lifeof monkeys, although in a measure experimental, is based upon relativelyfew and unsystematic observations as contrasted with those of Thorndikeand Kinnaman. It appears, however, that Hobhouse's experiments wereadmirably planned to test the ideational capacity of his subjects, andone can not find a more stimulating discussion of ideation than thatcontained in his "Mind in Evolution. " The results of his tests made witha _P. Rhesus_ monkey are similar to those of Kinnaman, for almost all ofthem indicate the presence and importance of ideas. 

Watson (1908) in tests of the imitative ability of _P. Rhesus_ sawrelatively little evidence of other than extremely simple forms ofideation. But in contrast with his results, those obtained by Haggerty(1909), in a much more extended investigation in which several speciesof monkey were used, obtained more numerous and convincing evidences ofideation in imitative behavior. Although this author wholly avoids theuse of psychological terms, seeking to limit himself to a strictlyobjective presentation of results, it is clear from an unpublishedmanuscript (thesis for the Doctorate of Philosophy, deposited in theLibrary of Harvard University) that he would attribute to monkeys simpleforms of ideational experience. 

Witmer (1910) reports, in confirmation of Haggerty's results, intelligently imitative behavior in _P. Irus_. 

The work of Shepherd (1910) agrees closely, so far as evidences ofideation are concerned, with that of Thorndike. He obviously strives forconservatism in his statements concerning the adaptive intelligence ofhis monkeys, all of which belonged to the species _P. Rhesus_. At onepoint he definitely states that they exhibit ideas of a low order, orsomething which corresponds to them. Satisfactory evidences of reasoninghe failed to obtain. 

Franz's (1907, 1911) studies of monkeys, unlike those mentioned above, have for their chief motive not the accurate description of variousfeatures of behavior but instead knowledge of the functions of variousportions of the brain. His results, therefore, although extremelyinteresting and of obvious value to the comparative psychologist, throwno special light upon the problem of ideation. 

The investigation by Hamilton (1911) of reactive tendencies in _P. Rhesus_ and _irus_ yielded preeminently important data concerningcomplex behavior. For the ingenious quadruple-choice method devised bythis observer showed that mature monkeys exhibit fairly adequate typesof response. As Hamilton's interest centered in behavior, he did notdiscuss ideation, but this does not prevent the comparison of his datawith those of the present report, and the agreement of his findings withmy own is obvious. 

My work contrasts sharply with that briefly mentioned above in that Iapplied systematically and over a period of several months anexperimental method suited to reveal problem solving ability. Previously, the so-called problem or puzzle-box method had been used asa means of testing for the presence of ideas. For this I substituted themultiple-choice method. One of the chief advantages of this new methodis the possibility of obtaining curves of learning for the solution orattempted solution of relational problems of varying difficultness. I amconfident that these curves of learning will prove far more valuablethan such data as are yielded by the puzzle-box method. 

The Pithecus monkeys, which I studied intensively, yielded relativelyabundant evidences of ideation, but with Thorndike I must agree that of"free ideas" there is scanty evidence; or rather, I should prefer tosay, that although ideas seem to be in play frequently, they are ratherconcrete and definitely attached than "free. " Neither in my sustainedmultiple-choice experiments nor from my supplementary tests did I obtainconvincing indications of reasoning. What Hobhouse has called articulateideas, I believe to appear infrequently in these animals. But on thewhole, I believe that the general conclusions of previous experimentalobservers have done no injustice to the ideational ability of monkeys. It is clearly important, however, that we always should take intoaccount the species of animal observed, for unquestionably there areextreme differences in mental development among the monkeys. 

As I view my results in the light of their relations to earlier work, Iam strongly impressed with the importance of the use of improved methodsfor the study of complex behavior. The delayed reaction method ofHunter, the quadruple-choice method of Hamilton, and my multiple-choicemethod offer new and promising approaches to forms of activity whichthus far have been only superficially observed. 

The ability exhibited by Skirrl to try a method out and then to abandonit suddenly is characteristic of animals high in intelligence. Most ofthe problems which I presented to my animals would be rated as difficultby psychologists, for as a rule they involved definite relations anddemanded on the part of the subject both perception of a particularrelation and the ability to remember or re-present it on occasion. 

I was greatly surprised by the slow progress of the monkeys toward thesolution of these problems. It had been my supposition that they wouldsolve them more quickly than any lower type of mammal, but as a matterof fact they succeeded less well than did pigs. Their behaviorthroughout the work proved that of far greater significance for theexperimenter than the solution of a problem is definite knowledge of themodes of behavior exhibited from moment to moment, or day to day. Thisis true especially of those incidental or accidental modes of responsewhich so frequently appeared in connection with my work that I came tolook upon them, the surprises of each day, as my chief means of insight. 

_Evidences of Ideation in Apes_

Reliable literature of any sort concerning the behavior and mental lifeof the anthropoid apes is difficult to find, and still more rare arereports concerning experimental studies of these animals. There are, itis true, a few articles descriptive of tests of mental ability, but eventhese are scarcely deserving of being classed as satisfactoryexperimental studies of the psychology of the ape. I have thesatisfaction of being able to present in the present report the firstsystematic experimental study of any feature of the behavior of ananthropoid ape. 

Among the most interesting and valuable of the descriptions which may beclassed among accounts of tests of mental ability is Hobhouse's (1915)study of the chimpanzee. The subject was an untrained animal, so far asstated, of somewhat unsatisfactory condition because of timidity. Nevertheless, Hobhouse was able to obtain from him numerous andinteresting responses to novel situations, some of which may be safelyaccepted as evidences of ideation of a fairly high order. 

Similar in method and result to the work of Hobhouse is that of Haggerty(unpublished thesis for the Doctorate of Philosophy, deposited in theLibrary of Harvard University). Haggerty's tests of the ability of youngorang utans and chimpanzees to solve simple problems and to use tools invarious ways yielded results which contrast most strikingly with thoseobtained in his experimental study of the imitative tendency in monkeys. His observations, had he committed himself to anything approachinginterpretation, doubtless would have led him to conclusions concerningthe ideational life of these animals very similar to those of Hobhouse. 

Koehler, working in the Canary Islands, has, according to informationwhich I have received from him by letter, made certain experiments withorang utans and chimpanzees similar to those of Hobhouse and Haggerty. His results I am unable to report as I have scanty informationconcerning them. They are, presumably, as yet unpublished. 

In his laboratory at Montecito, California, Hamilton has from time totime kept anthropoid apes, but without special effort to investigatetheir ideational behavior. He has most interesting and valuable dataconcerning certain habits and instincts, all as yet unpublished. 

To a congress of psychologists Pfungst (1912) briefly reported on workwith anthropoid apes in certain of the German zoölogical gardens. Hispreliminary paper does not enable one to make definite statementsconcerning either his methods or such results as he may have obtainedconcerning ideational behavior. So far as I know, he has not as yetpublished further concerning his investigation. 

Möbius (1867) has described interesting observations concerning themental life of the chimpanzee. But this, like all of the work previouslymentioned, is rather in the nature of casual testing than thoroughgoing, systematic, and analytic study. 

In addition to the above reports, there are a few concerning thebehavior of apes which have been especially trained for purposes ofexhibition. Most interesting of these is that of Witmer (1909), whostudied in exhibitions and in his own laboratory the behavior of thechimpanzee Peter. The varied forms of intelligently adaptive behaviorexhibited by this ape convinced Witmer of ideational experience and evenof an approach to reasoning. In his brief report he expresses especialinterest in the possibility of educating this "genius among apes" to theuse of language. 

A chimpanzee named Consul was observed several years ago by Hirschlaff(1905), and his tricks were interestingly described from the pedagogicalstandpoint. 

Similar in character is Shepherd's (1915) brief description of the stagebehavior of Peter and Consul, both chimpanzees. It is impossible todetermine from the account whether these animals are the same as wereobserved by both Witmer and Hirschlaff. As no reference is made inShepherd's paper to other descriptions of the behavior of these animalsand as he adds nothing to what had already been presented, the readerobtains no additional light on ideation. 

I have mentioned only samples of the articles on trained anthropoids. All are necessarily descriptions of the behavior of individuals who hadbeen trained not for psychological purposes but for the vaudevillestage, and although such observations unquestionably have certain valuefor comparative psychology, it is well known that unless an observerknows the history of an act, he is not able to evaluate it in terms ofintelligence and is especially prone to overestimate its value asevidence of ideation. 

There remain studies of the apes, dealing primarily with behavior andmental characteristics, which are slightly if at all experimental anddeserve to be ranked as naturalistic accounts. Such is, for example, thebook of Sokolowski (1908), in which attention is given to thecharacteristics of young as well as fairly mature specimens of thegorilla, chimpanzee and orang utan. 

The various publications of Garner (1892, 1896, 1900) deal especiallywith the language habits of monkeys and apes, but observations bearingon ideation are reported. 

Wallace (1869) describes certain features of the behavior of an infantorang utan whose mother he shot in Borneo. He also reports observationsconcerning the behavior of adult orang utans, many specimens of whichwere shot by him during his travels. 

Early in the last century, Cuvier (1810) interested himself in studiesof the intellectual characteristics of the orang utan, and his data, taken with those of Wallace, Sokolowski, and others similarly interestedin the natural history of mind, give one a valuable glimpse of the lifeof the anthropoid ape. 

Finally, the data brought together by Brehm (1864, 1875, 1888) in hisfamous Tierleben; by Darwin (1859, 1871) in "The Origin of Species, " andother works, by Romanes (1900), especially in his books on mentalevolution, by C. Lloyd Morgan (1906) in his several works on comparativepsychology, and by Holmes (1911) in his discussion of the evolution ofintelligence, contribute not unimportantly to our all too meagreknowledge of the mental life of the anthropoid apes. 

My own results, viewed in the light of what one may learn from theliterature, stand out as unique because of the method of research. Neverbefore, so far as I have been able to learn, has any ape been subjectedto observation under systematically controlled conditions for so long aperiod as six months. Moreover, my multiple-choice method has the meritof having yielded the first curve of learning for an anthropoid ape. This fact is especially interesting when one considers the nature of theparticular curve. For so far as one may say by comparing it with thecurves for various learning processes exhibited by other mammals, it isindicative of ideation of a high order, and possibly of reasoning. I donot wish to exaggerate the importance of my results, for as contrastedwith what might be obtained by further study, and with what must beobtained if we are adequately to describe the mind of the orang utan, they are meager indeed. 

Especially noteworthy, as evidences of ideation, in the results yieldedby the multiple-choice method are (1) the use by the orang utan ofseveral different methods in connection with each problem; (2) thesuddenness of transition from method to method; (3) the final andperfect solution of problem I without diminution of the initial errors;(4) the dissociation of the act of turning in a circle from that ofstanding in front of a particular box. 

To these features of behavior others of minor importance might be added. But as they have been sufficiently emphasized in the foregoing detaileddescriptions, I need only repeat my conclusion, from the summation ofevidence, that this young orang utan exhibited numerous free ideas andsimple thought processes in connection with the multiple-choiceexperiment. His ultimate failure to solve the second problem ispeculiarly interesting, although in the light of other features of hisbehavior by no means indicative of inferior intelligence. 

The various supplementary experimental tests which I employed are in nowise importantly distinguished from those used by other observers. Thebox stacking experiment has, according to my private information, beenused by Koehler. It is obviously important that such tests be applied inthe same manner to individuals not only of the different genera ofanthropoid apes, but of different ages, sex, and condition of training. 

The box stacking experiment, although it yielded complete success onlyas a result of suggestion on my part, proved far more interesting duringits progress than any other portion of my work. In connection with it, the orang utan exhibited surprisingly diverse and numerous efforts tomeet the demands of the situation. It is fair to characterize him asinventive, for of the several possible ways of obtaining the bananawhich were evident to the experimenter, the ape voluntarily used all buttwo or three, and one of these he subsequently used on the basis ofimitation. 

Had Julius been physically and mentally mature, my results wouldundoubtedly have been much more impressively indicative of ideas, buteven as matters stand, the survey of my experimental records andsupplementary notes force me to conclude that as contrasted with themonkeys and other mammals, the orang utan is capable of expressing freeideas in considerable number and of using them in ways highly indicativeof thought processes, possibly even of the rational order. Butcontrasted with that of man the ideational life of the orang utan seemspoverty stricken. Certainly in this respect Julius was not above thelevel of the normal three-year-old child. 

In common with other observers, I have had the experience of beingprofoundly impressed by the versatility of the ape, and however much Imight desire to disprove the presence of free ideas and simple reasoningprocesses in the orang utan, I should feel bound to accept many of theresults of my tests as evidences of such experience. 

I have attempted to indicate briefly the historical setting of myinvestigation. I propose, now, in the concluding section, to lookforward from this initial research and to indicate as well as I may in afew words the possibilities of results important for mankind from thethorough study of the monkeys and anthropoid apes. 

VII

PROVISION FOR THE STUDY OF THE PRIMATES, AND ESPECIALLY THE MONKEYS ANDANTHROPOID APES[1]

[Footnote 1: Much of the material of this section was publishedoriginally in _Science_ (Yerkes, 1916). ]

I should neglect an important duty as well as waste an opportunity if inthis report I did not call attention to the status of our knowledgeconcerning the monkeys and apes and present the urgent need of adequateprovision for the comparative study of all of the primates. 

Although for centuries students of nature have been keenly interested inthe various primates, the information which has been accumulated isfragmentary and wholly inadequate for generally recognized scientificand practical needs. There is a voluminous literature on many aspects ofthe organization and lives of the monkeys and apes, but when onesearches in it for reasonably connected and complete descriptions of theorganisms from any biological angle, one, is certain to meetdisappointment. 

Concerning their external characteristics we know much; and ourclassifications, if not satisfactory to all, are at least eminentlyuseful. But when one turns to the morphological sciences of anatomy, histology, embryology, and pathology, one discovers great gaps, whereknowledge might reasonably be expected. Even gross anatomy has much togain from the careful, systematic examination of these organisms. Withstill greater force this statement applies to the studies of finerstructural relations. Little is known concerning the embryologicaldevelopment and life history of certain of the primates, and almostnothing concerning their pathological anatomy. 

Clearly less satisfactory than our knowledge of structure is the statusof information concerning those functional processes which are thespecial concern of physiology and pathology. Certain importantexperimental studies have been made on the nervous system, but rarelyindeed have physiologists dealt systematically with the functions ofother systems of organs. There are almost no satisfactory physiologicaldescriptions of the monkeys, anthropoid apes, or lower primates. 

SUB-DIVISIONS OF THE ORDER PRIMATES

_Order_ _Sub-orders_ _Families_

, - a. PROSIMII (Lemurs and Aye-Ayes) | |, - i. Hapalidae (Marmosets) | | ii. Cebidae (Howling Monkeys, PRIMATES -+ | Tee Tees, Squirrel Monkeys, | | Spider Monkeys, and Capuchin | | Monkeys) `- b. ANTHROPOIDEA ... -+ iii. Cercopithecidae (Baboons | and Macaques) | iv. Simiidae (Gibbons, Orangs, | Chimpanzees, and Gorillas) `- v. Hominidae (Man)

When we turn to the science of genetics we meet a similar condition, forthe literature reveals only scattered bits of information concerningheredity in the primates. No important experimental studies alonggenetic lines have been made with them, and such general observationsfrom nature as are on record are of extremely uncertain value. Were oneto insist that we know nothing certainly concerning the relation ofheredity in other primates than man, the statement could not well bedisputed. 

Occasionally in recent years students of human diseases have employedmonkeys or apes for experimental tests, but aside from the isolatedresults thus obtained, extremely little is known concerning the diseasespeculiar to the various types of infra-human primates or the significantrelations of their diseases to those of man. 

Next in order of extent to our morphological knowledge of theseorganisms is that of their behavior, mental life, and social relations. But certainly no one who is conversant with the behavioristic, psychological and sociological literature could do otherwise thanemphasize its incompleteness and inadequacy. For our knowledge ofbehavior has come mostly from naturalistic observation, scarcely at allfrom experimentation; our knowledge of social relations is obviouslymeager and of uncertain value; and finally, our knowledge of mind isbarely more than a collection of carelessly drawn inferences. 

This picture of the status of scientific work on the primates, althoughnot overdrawn, will doubtless surprise many readers, and even thebiologist may find himself wondering why we are so ignorant concerningthe lives of the organisms most nearly akin to us, and naturally ofdeepest interest to us. The reasons are not far to seek. Most scientificinvestigators are forced by circumstances to work with organisms whichare readily obtained and easily kept. The primates have neither of theseadvantages, for many, if not most of them, are expensive to get andeither difficult or expensive to keep in good condition. Clearly, then, our ignorance is due not to lack of appreciation of the scientific valueof primate research but instead to its difficultness and costliness. 

Strangely enough, the practical importance of knowledge of the primateshas seldom been dwelt upon even by those biologists who are especiallyinterested in it. It is, therefore, appropriate to emphasize thestrictly human value of the work for which I am seeking provision. 

During the past few years it has been abundantly and convincinglydemonstrated that knowledge of other organisms may aid directly in thesolution of many of the problems of experimental medicine, ofphysiology, genetics, psychology, sociology, and economics. In the lightof these results, it is obviously desirable that all studies ofinfrahuman organisms, but especially those of the various primates, should be made to contribute to the solution of our human problems. 

To me it seems that thoroughgoing knowledge of the lives of theinfrahuman primates would inevitably make for human betterment. Throughthe science of genetics, as advanced by experimental studies of themonkeys and anthropoid apes, practical eugenic procedures should be moresafely based and our ability to predict organic phenomena greatlyincreased. Similarly, intensive knowledge of the diseases of the otherprimates in their relations to human diseases should contributeimportantly to human welfare. And finally, our careful studies of thefundamental instincts, forms of habit formation, and social relations inthe monkeys and apes should lead to radical improvements in oureducational methods as well as in other forms of social service. 

Along theoretical lines, no less than practical, systematic researchwith the primates should rapidly justify itself, for upon its resultsmust rest the most significant historical or genetic biologicaldescriptions. It is beyond doubt that genetic psychology can best beadvanced to-day by such work, and what is obviously true of this scienceis not less true of all the biological sciences which take account ofthe developmental or genetic relations of their events. 

In view of the probable values of increasingly complete accounts ofprimate life, it seems far from extravagant to insist that the securingof adequate provision for systematic and long continued research is themost important task for our generation of biologists and the one whichwe shall be least excusable for neglecting. Indeed, when one stops toreflect concerning the situation, it seems almost incredible that thetask has not been accomplished. 

Some ten years ago Professor John B. Watson (1906) entered a plea forthe founding of a station for the experimental study of behavior. Hemade no special mention of work with the monkeys and apes, but it isclear from the problems which he enumerates that he would consider themmost important subjects for observation. Professor Watson's plea hasapparently been forgotten by American biologists, and it seems notinappropriate to revive it at this time. For surely we have advancedsufficiently along material and scientific lines during the last tenyears to render possible the realization of his hope. 

To my knowledge, only one definite attempt has thus far been made togain special provision for the study of the primates. Somewhere aboutthe year 1912 there was established on Tenerife, one of the CanaryIslands, a modest station for the study of the anthropoid apes. I havealready referred to it briefly on page 1. The plan and purpose of thisstation, which is of German origin, have been presented briefly byRothmann (1912). From personal communications I know that a singleinvestigator has been in residence at the station since its founding andthat psychological and physiological results of value have beenobtained, but no published reports have come to my attention. 

When I first heard of the existence of the German anthropoid station Inaturally thought of the possibility of coöperative work, but the eventsof the past two years have rendered the chances of cooperation so remotethat it now seems wholly desirable and indeed imperative to seek theestablishment of an American station, which, unlike the German station, shall provide adequately not only for the study of the anthropoid apesbut for that of all of the lower primates. It should be the function ofsuch a station or research institute (1) to bring together and correlateall the information at present available; (2) to fill in existing gapsobservationally and thus complete and perfect our knowledge of theseorganisms; (3) to seek to bring all available information to bear uponthe problems of human life. 

Hitherto the unsatisfactoriness of progress has been due to the lack ofa definite plan and program. Every investigator has gone his own way, doing what little his personal means and opportunity rendered possible. The time has at last come when concerted action seems feasible as wellas eminently desirable. I am therefore offering a plan and programwhich, if wisely developed, should lead ultimately to fairly completeand practically invaluable knowledge of the lives of all of theprimates. There should be provided in a suitable locality a station orresearch institute which should offer adequate facilities (1) for themaintenance of various types of primate in normal, healthy condition;(2) for the successful breeding and rearing of the animals, generationafter generation; (3) for systematic and continuous observation underreasonably natural conditions; (4) for experimental investigations fromevery significant biological point of view; (5) for profitablecooperation with existing biological institutes or departments ofresearch throughout the world. 

The station should be located in a region whose climate is highlyfavorable to the life of many of the lower primates as well as to thatof man. Such a location is by no means easy to find. Because of myintense interest in the subject, I have, during the past five years, prospected in various parts of the world for a satisfactory site. Ishall now attempt to indicate the chief requirements and also theforemost advantages and disadvantages of several regions which have beenconsidered. It is first of all requisite that the climate be such as toagree with the organisms to be studied and such, also, as to rendertheir breeding normal and dependable. Second in importance is itssatisfactoriness for the life and scientific productiveness of theobserver. While certain tropical localities would meet the firstrequirement perfectly, they would prove extremely unsatisfactory forresearch activity. It therefore seems essential to find a region whoseclimate shall reasonably meet the needs of the experimenter whileadequately meeting those of the animals to be studied. 

A further factor which has important bearing upon the productiveness ofthe observer is the degree of isolation from civilization and from otherscientific work. No scientist can long work effectively, even in areasonably healthy and stimulating climate, if entirely cut off fromsimilar interests and activities. It is therefore desirable, if at allpossible, to discover a location in the midst of civilization and withreasonably good opportunities for scientific associations. 

With these several desiderata before us, I shall call attention to anumber of possible sites for a station, several of which I have visited. Southern California, and especially the portion of the State betweenSanta Barbara and San Diego, promises fairly well. It is definitelyknown that certain, if not all, species of monkey will breed therefairly satisfactorily, and although it has not yet been demonstrated, there is no reason to suppose that in certain regions the anthropoidapes might not also be kept in perfect health and successfully bred. Themain advantages of this general region are (a) a climate which promisesto be reasonably satisfactory for many if not all of the primates; (b)admirable climatic conditions for investigators; (c) wholly satisfactoryscientific and cultural environment for the staff of a station. The mostsignificant disadvantages are (a) a temperature, which is at times atrifle too low for the comfort of certain of the monkeys and apes. It isby no means certain, however, that they would not usually adaptthemselves to it. (b) The necessity of importing all of the animals andof having to rely upon successful acclimatization. Of course it is to beassumed that importation would be necessary only at the outset of suchwork, since the animals later should replenish themselves within theconfines of the station. 

Florida offers possibilities somewhat similar to those of southernCalifornia, but as I have not had opportunity to examine the conditionsmyself, I can say only that in view of such information as is availablethe advantage seems to be greatly in favor of the latter. 

Cuba, Jamaica, Porto Rico, and for that matter, several of the WestIndies, offer possible sites for a successful station. I have reasonablyintimate personal knowledge only of the conditions in Jamaica. The majoradvantages in the West Indies are (a) suitable climatic conditions andfood supply for the animals; and (b) reasonably satisfactory climaticconditions for the staff. These are, however, more than counterbalancedin my opinion by the following serious disadvantages: (a) the relativeisolation of the investigators from their fellow scientists; (b) thenecessity of importing all of the animals originally used; (c) the riskof destruction of the station by storms. 

It is definitely known that anthropoid apes as well as monkeys can besuccessfully kept, bred, and reared in the West Indies. During the pastyear, on the estate of Doha Rosalia Abreu, near Havana, Cuba, achimpanzee was born in captivity. A valuable account of this importantevent and of the young ape has been published by Doctor Louis Montané(1915). It therefore seems practically certain that regions could befound readily on Jamaica, Porto Rico, or smaller islands, which would beeminently satisfactory for the breeding of apes. 

There are obvious reasons why an American station for the study of theprimates should be located on territory controlled by the United StatesGovernment, and if a tropical location proves necessary, it wouldprobably be difficult to find more satisfactory regions, aside from theinconveniences and risk of importation and the relative isolation of theinvestigators, than are available on Porto Rico. 

I have not seriously considered the possibility of locating an Americanstation on the continent of Africa, for although two of the mostinteresting and important of the anthropoid apes, the gorilla and thechimpanzee, are African forms, while many species of monkey are eitherfound there or could readily be imported, it has seemed to me that theislands of the West and East Indies and the portions of the UnitedStates referred to above are much to be preferred over anythingavailable in Africa. 

In the East, Borneo, the Philippine Islands, and Hawaii are well worthconsidering. Borneo is the home of the gibbon and of at least onespecies of orang utan, and in addition to these important assets, itpresents the advantages of (a) a wholly suitable climate and food supplyfor monkeys and apes; and (b) climatic conditions for investigatorswhich, I am informed by scientific friends, are nearly ideal. Forinvestigators the most serious disadvantage here, as in all other partsof the East, would be the isolation from other scientific work andworkers. 

The possibilities of Central America I considered several years ago whenit seemed to me possible that work might profitably be done with monkeysand apes on the Canal Zone. The advantages are (a) a climate whichpromises fairly well for the animals; and (b) reasonable accessibilityfrom the United States. The disadvantages are (a) a far from idealclimate for long continued scientific work; and (b) an environment whichfrom the cultural and scientific point of view leaves much to bedesired. 

Were a permanent psycho-biological station for the study of the primatesto be established in southern California, it would, even though whollysatisfactory conditions for the breeding, rearing, and studying of theanimals were maintained, furnish more or less inadequate opportunity forthe observation of the animals under free, natural conditions. It wouldtherefore be necessary, to supplement the work of such a station byfield work in Borneo, Sumatra, Africa, India, South America, and suchother regions as the species of organism under consideration happen toinhabit. 

Considering equally the needs of the experimenter and the demands of theanimals, it seems to me reasonable to conclude that southern Californiashould be definitely proved unsuitable before a more distant site wereselected. For the information which I have been able to accumulateconvinces me that it would in all probability be possible successfullyto breed and keep the primates there, and it is perfectly clear that insuch event the output of a station would be enormously greater becauseof the more favorable conditions for research than in any tropicalregion or in a more isolated location. 

Assuming that satisfactory provision in the shape of a scientificestablishment for the study of the primates in their relations to manwere available, the following program might be followed: (1) Systematicand continuous studies of important forms of individual behavior, ofsocial relations, and of mind; (2) experimental studies of physiologicalprocesses, normal and pathological, and especially of the diseases ofthe lower primates, in their relations to those of man; (3) studies ofheredity, embryology, and life history; (4) research in comparativeanatomy, including gross anatomy, histology, neurology, and pathologicalanatomy. 

Each of these several kinds of research should be in progress almostcontinuously in order that no materials or opportunities for observationbe needlessly wasted. Because of the nature of the work, it would benecessary to provide, first of all, for those functional studies whichdemand healthy and normally active organisms, whose life history isintimately and completely known. This is true of all studies inbehavior, whether physiological, psychological, or sociological. Simultaneously with behavioristic observations and often upon the sameindividuals, genetic experiments might be conducted. This would beextremely desirable because of the relatively long periods betweengenerations. After the usefulness of an animal in behavioristic orgenetic inquiries had been exhausted, it might be made to render stillfurther service to science in various experimental physiological, ormedical inquiries. And finally, the same individual might ultimately beused for various forms of anatomical research. Thus, it is clear thatthe scientific usefulness of a lemur, a monkey, or an ape might bemaintained at a high level throughout and even beyond the period of itslife history. 

The program thus briefly sketched would provide either directly orindirectly for work on every aspect of primate life. Especiallyimportant would be the intimacy of interest and cooperation amonginvestigators, for the comparative method should be applied consistentlyand to the limit of its value. The results of various kinds ofobservation should be correlated so that there should ultimately emergea unitary and practically valuable account of primate life, to replacethe patchwork of information which we now possess. 

Because of the costliness of maintaining and breeding the monkeys andapes, it is especially desirable that the several kinds of researchmentioned above should be conducted. Indeed, it would seem inexcusablywasteful to attempt to maintain a primate or anthropoid station forpsychological observations alone, or for any other narrowly limitedbiological inquiry. 

Furthermore, the station should be permanent, since for many kinds ofwork it would be essential to have intimate knowledge of the lifehistory and descent of an individual. With the lower primates, ageneration might be obtained in from two to five years; with the higher, not more frequently, probably, than from ten to fifteen years. Ittherefore seems not improbable that the value of the work done in such astation would continue to increase for many years and would not reachits maximum short of fifty or even one hundred years. 

A staff of several highly trained and experienced biologists would beneeded. The following organization is suggested as desirable, although, as indicated below, not necessarily essential in the beginning: (1) Anexpert especially interested in the problems of behavior, psychology, and sociology, with keen appreciation of practical as well as oftheoretical problems; (2) an assistant trained especially in comparativephysiology; (3) an expert in genetics and experimental zoology; (4) anassistant with training and interests in comparative anatomy, histology, and embryology; (5) an expert in experimental medicine, who couldconduct and direct studies of the diseases of man as well as of thelower primates and of measures for their control; (6) an assistanttrained especially in pathology and neurology. 

To this scientific staff of six highly trained individuals there shouldbe added a business manager, a clerical force of three individuals, askilled mechanician, a carpenter, and at least four laborers. 

The annual expenditures of an institute with such a working staff, wouldin southern California, approximate fifty thousand dollars. It wouldtherefore be necessary that it have an endowment of approximately onemillion dollars. 

In the absence of this foundation it would, of course, be possible tomake a reasonably satisfactory beginning on the work which has beenoutlined in the following less expensive manner. A working plant mightbe established, on ground rented or purchased at a low figure, for aboutten thousand dollars; the salary of a director, assistants, a clericalhelper, and combined mechanic and laborer might be estimated at the samefigure; the cost of animals and of maintenance of the plant wouldapproximate five thousand dollars. Thus, we should obtain as an estimateof the expenditures for the first year twenty-five thousand dollars. Without expansion, the work might be conducted during the second yearfor fifteen thousand dollars, and subsequently it might be curtailed orexpanded, resources permitting, according as results achieved and inprospect justified. 

An institute established on such a modest basis as this still mightrender largely important scientific service through its own research andthrough organized cooperation with other existing researchestablishments. Thus, for example, supposing that behavioristic, psychological, sociological, and genetic inquiries were conducted in theinstitute itself, animals might be supplied on a mutually satisfactorybasis to institutes for experimental medicine, for physiologicalresearch, and for anatomical studies. Under such conditions, it isconceivable that extremely economical and good use might be made of allthe available primate materials. But it is not improbable that evencoöperative research would prove on the whole more profitable, exceptpossibly in the case of morphological work, if investigators couldconduct their studies in the institute itself rather than in distantlaboratories. In any event, the idea of coöperation should be prominentin connection with the organization of a research station for the studyof the primates. For thus, evidently, scientific achievement inconnection with these important types of animal might be vastlyincreased over what would be possible in a single relatively smallinstitution with a limited and necessarily specialized staff of workers. 

Despite the fact that biologists generally recognize the importance ofthe work under consideration and are eager to have it done, it isperfectly certain that we shall accomplish nothing unless we devoteourselves confidently, determinedly and unitedly, with faith, vision, and enthusiasm, to the realization of a definite plan. Our vision isclear, --if we are to gather and place at the service of mankind adequatecomparative knowledge of the life of the primates and if we are to makethis possible harvest of scientific results count for human betterment, we must bend all our efforts to the establishment of a station orinstitute for research. 

VIII

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