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

l, Pithe

First at

ion was undertaken early in April with Skirrl, Sobke, and Julius. The results for each of th

ommend him to me for further study because of his mental peculiarities. With me he was from the first frank, aggressive, and inclined to be savage. It was soon possible for me to go into the large cage, Z, with him and allow

trance and exit doors of box 7 raised, the monkey was allowed to pass into the reaction-compartment E and thence through box 7 to the food cup. As soon as he had finished eating, he was called back to D b

s equally unsuccessful in either driving or tempting him with food into the apparatus. But on April 14 he was so hungry that he was finally lured in by the use of food. He cautiously approached the boxes and attempted to climb through on the sides instead of walking on the floor. It was perfectly evident that he had an instinctive or an acquired fear of the white surfaces. As the matter was of prime importance for the success of my work, I inquired of Doctor Hamilton, and of the men in charge of the cages, for any i

apidly, and on April 15, by covering the floor with sawdust, I so diminished the influence of the whiteness as to render the preliminary tra

certain group of boxes, admitted the animal to the reaction-chamber, punished incorrect choices by confining the animal for thirty seconds, and rewarded correct choices by raising the exit door and thus permitting escape and the obtaining of food. The trials were given in rapid succession, and the total time re

ed to the reaction-chamber immediately chose box l. Having received the reward of food, he was called back to D, and doors 8 and 9 having been raised in preparation for the next trial, he was again admi

son of the reactions of different types of organism in this experiment, to present the detailed records for each trial, tab

following ten columns present respectively the results of the trials for each of the ten settings. Each number, in these results, designates a box entered. At the extreme right of the table are three columns which indicate, first, the nu

reads 9.8. In trial 3, setting 3, he chose incorrectly twice before finally selecting the right box. The record reads 6.7.3, and so on throughout the ten trials which constitute a series. The summary for this series indicates three right and seven wrong first choices, that is, three cases in which the right box was entered first. The ratio of right to wrong first choices is therefore 1 t

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kirrl, P. iru

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 |

End of seri

of setting 1, which was presented to the animal in trials numbered 1, 11, 21, and so on to 141, it is clear from the records that no definite improvement occurred. But oddly enough, in the case

es is inversely proportional to the number of doors in use, while the number of ch

able, but on the whole the experiment seemed fairly satisfactory. Cold, cloudy, or rainy days tended to diminish steadiness a

rupted by a severe storm, the noise of which so distracted the monkey that he ceased to work. Consequently, observations were interrupted on the completion of trial 132, and on May 5, the series was begun with setting 3. On this dat

position or the number of doors in the group presented, a control series was given in which the settings differed from the regular seri

react to particular settings. A careful study of all of the data of response, together with notes on the varied behavior of the animal during the experiments, justifies the statement that Skirrl's solution of problem 1 was incomplete a

he chief points of method clear. It will be needless, hereafter, to refer explicitly to many of the chara

e most striking, and fairly indicate the erraticness of the animal. The curve is based upon the data in next to the

n the group, and in case it happened to be a wrong one, of choosing, on emergence from it, the next toward the right end of the group, and so on down the line. Having reached the extreme right end, the tendency was to follow the side of the reaction-chamber around to the opposite end and to enter the first box at the left end of the group, which was, of course, th

ves of learning for the solution of

ley I, instead of toward the left, through G and H, to D. In contrast with the other animals, he spent much time before the closed doors of the boxes, instead of going directly to the open doors, some one of which marked the box in which the reward

econd from t

he animal was merely fed in the boxes each day. This was done in order that he should partially lose the effects of his previo

by the experimenter to find the right box. He persistently, as appears in the first line of records of table 2, entered the first box at the left. The series was continued on May 13, but with very unsatisfactory results, since he apparently had been greatly discouraged by the unusual diffi

ese fifty open doors may be defined as right ones, the expected ratio of right to wrong first choices in the absence of previous

t seemed at the moment a peculiarly unfortunate accident, but in the lig

ent to the open door of box 1 and peered in, or peered down through the hole in the floor which received the staple on the door. He refused to enter any one of the open boxes and continued, at intervals of every half minute or so, his cries. For thirty minutes I waited, hoping to be able to induce him to complete the series of trials, but in vain. Although it was obvious that he was eager to escape from the apparatus, he would not e

he several doors, had used nails instead of screws for attaching staples underneath the floor and had neglected to clinch the nails. Skirrl, in the dim light of the box, doubtless stepped upon one of the nails and inflicted a painful, although not serious, injury upon himself. It was impossible for

dure was to coax him through one box after another by standing at the exit door with some tempting morsel of food. After several days of this treatment, he again trusted himself to the boxes, although very circumspectly and only when both entrance and exit doors were raised. Not until May

ry careful in locking the doors, since the sound of the bar sliding beneath the floor often frightened and caused him to quit work. Day after day the tendency to peer through the holes in th

monkey, there was substituted for it on June 1 the punishment of forcing him to work his way out of each wrong box by raising the entra

t worked unsatisfactorily and had to be abandoned. During this series, the animal was startled by

re the use of banana, grapes, peanuts, and other eagerly sought foods in varying quantities, and in the latter are included periods of confinement ranging from ten seconds

iverted and even when extremely hungry, often stopped work in the middle of an early

sterisk to indicate that aid was given by the experimenter, and second, in that two additional columns, headed, respectively, R and W, are presented. These give the right and wrong first choices for each day, whereas t

re are remarkable contrasts in the results for different settings as they appear in their respective vertical columns. Thus, in the case of setting 1, after the first trial mistakes became relatively infrequent, whereas in se

e described as follows: (a) choice of the first box at the left; (b) random choice with tendency to choose first, a box near the midd

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kirrl, P. iru

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 |

ason of aid from the experimenter are no

Aided by ex

t developed early,-after about one hundred trials; in setting 3, after about one hundred and fifty trials; in setting 4, after about one hundred and fifty trials; in setting 5, after about one hundred and seventy trials; in setting 6

olly overcome at the conclusion of the experiment. In the case of the series of trials given on June 8, numbered 191

could appear, in problem 2, as right boxes. In trials 601 to 610, given on July 7, there occurred partial return to the formerly established method of choosing the first door at t

ui and often would refuse to work and simply sit before the open doors yawning. T

keep him in good physical condition. An increase in the number of correct choices promptly resulted, and continued until on July 14 the ratio of choices was 1 to .54. It appeared from these d

t became clear that the period of thirty seconds, combined with a liberal reward in the shape of desired food and a single series of ten trials per

no outcry, but as soon as he was out of the box, sat down, and taking up his right hind foot, examined it for a few seconds. Having apparently assured himself that nothing serious had happened, he went on unconcernedly about his task. The presumption is that the sound of the lock-bar, associated as it was with his painful experience in box 1, revived the strongly affective experience of stepping on the nail. Psychologically

made in box 8, which, as it happened, had proved a peculiarly easy one for him throughout the training, since from the first he tended to avoid door 9. Consequently, it is only fair to conclude, from the results for this control series and for those given on August 11 and 12, that the animal chose not on the basis of a

cated. Consequently, the form of the curve is determined chiefly by the first series per day. The extreme irregularities of this curve are most interesting and puzzling, as are also the variations in the daily ratios of right to wrong first choices. Three times in the course of the training, this ratio rose to 1 to 9, or higher. The causes for such extreme variations are not easily enumerated, but a few of the most

yed a part in the solution of the problem is probable, but at best they functioned very ineffectively. The small number of methods used in the selection of the right box, and the slight var

es of learning for the solution of p

tely First at Left

aining and regain his customary interest in the apparatus by being allowed to obtain food easily instead of by dint of hard labor,-labor which was harder by far, apparently, than physical activity becaus

he first door at the right of the group, was begun August 19, and for nine days a single series of t

es. The right choices were due to the monkey's strong tendency to go first to the first door at the right and thence to the one next to it. Indeed in the series given on August 24; this method was followed without variation. In other words, in every one of the ten trials Skirrl entered first the box at the extreme right end of the group. This necessarily resulted in as many right as wrong firs

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kirrl, P. iru

| | | 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

Aided by ex

, Pithec

First at

d out and lured into the apparatus with food. Whereas Skirrl was frank and rather aggressive, Sobke was stealthy in his movements, furtive, and evidently suspicious of the experimente

each of the nine boxes. The procedure was simple. The entrance door and the exit door of a particular box were raised and the animal admitted to the reaction-compartment and permitted to pass through the box whose doors stood open, take its food, and return to the star

usually not more than a tenth of a medium sized banana for each correct choice. The total time for the first series of trials was fourteen minutes. This indicates that Sobke worked rapidly. My notes record that he worked quick

o such irregularities of behavior as appeared in the case of Skirrl, and consequently the description of results is a re

's first series was 1 to .67. This surprisingly good showing is unquestionably due to his marked tendency to choose the end box of a group; and this tendency, in turn, may in part be the result of the preliminary training, fo

ded markedly different results in the two positions. For whereas no mistakes were made in the case of setting 1, there were fifty per cent of incorrect first choices for setting 10. Again, satisfactory explanation is impossible. It is conceivable tha

1 to 80, only correct first choices appear. Consequently, seventy trials were required for the solut

a great din. Nevertheless, he worked steadily and well up to the sixth trial, which was preceded by a slight delay because of the necessity of refilling some of the food boxes. After this interruption, wrong ch

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bke, P. rhesus

+==============+==============+==============+==============+====

.4 | S.5 | S.6 | S.7 | S.8

| | | | | | | |

.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5

-------+-------+-------+-------+----

| | | | | |

| 6.2 | 6 | 7.5 | 4 | 9.7

| 2 | 6 | 7.5 | 8.4 | 9.9.7

9.7 | 2 | 6 | 5 | 8.4 | 7 |

| 6.2 | 6 | 6.5 | 4 | 7 | 3

| 2 | 6 | 5 | 4 | 9.7 | 3

.7 | 2 | 6 | 5 | 4 | 7 | 2

7 | 2 | 6 | 5 | 4 | 7 | 3

7 | 2 | 6 | 5 | 4 | 7 | 1

-------+-------+-------+-------+----

2.3.4 | | | 1.

8.9 | 6.7.8.9 | 1.2.3.4.5 | 5.6.7.8 |

----+-------+-------+-------+-

4 | 6 | 5.4.1 | 2 | 3 |

| 6 | 2.1 | 2 | 3 | 5 |

| | | | |

+==============+==============+==============+==============+====

t is evident that Sobke's solution of problem 1 is reasonably adequate. He is easily diverted or disturbed in his work by any unusual circumstances, but so long as everything goes smoothly, he chooses with ease and certainty. Whether it is fair to describe the behavior as in

blem than did Skirrl. The contrast in the learning processes of the two monkeys could scarcely be better exhibited than by the curves of learning which are presented in figure 18. The first, that for Sobke, is surprisingly r

econd from t

work quietly, fairly deliberately, and very steadily. His timidity had diminished and he would readily come to the experimente

hese four days the monkey was allowed to get food once from each of the nine boxes, both doors of a given box being open for the trial and

istakes in a trial, and of then, if need be, indicating the right box by slightly and momentarily raising the exit door. Every trial in which aid was thus given by the experimenter is indicated in table 5 by an asterisk following the last choice. In the first series of trials for this problem, aid had to be given in seven of the ten trials, and even so the series occupied seventy-one minutes. It is possible that had no aid been given, th

e noise of the rain on the roof frightened Sobke. He refused to work after the fourth trial, and the series

right door. He might, for example, make a number of incorrect choices, then pause for a few seconds to look steadily at the doo

oosing became definite and fairly precise. He was deliberate, quiet, and

been ten to fifteen seconds. This increase apparently did not disturb the monkey, for he continued to work perfectly throug

minutes. Sobke immediately stopped working, and he could not be induced to make any choices until Doctor Hamilton had left the room. This well indicat

nfinement as punishment to sixty seconds. In the meantime, it had sometimes been evident that Sobke was near to the solution of his problem. He

food in the apparatus. When the rewards obtained in the several trials did not satisfy his hunger, additional food was presented, on the completion of the series of experiments, in one or more of the food cups. On days marked by unwillingness or refusal to work, very little food was give

near at hand. This fact the experimenter recorded in his daily notes, and sure enough, on the following day Sobke chose correctly

in a tendency which although previously profitable no longer yields satisfaction, whereas in the crow, pig, rat, and ring dove, the unprofitable mode of response tends to persist during a relatively large number of trials. (b) The tendency to choose, first, a box near the left end of the group, to go from that to the box at the extreme right end of the group, thence to the one next in order, which was, of course, the right box. This tendency appears fairly clearly from May 7th on. (c) The box at the extreme right was first chosen and then the one next to it. For example, in setting 2, box

in irregularities and the order as well as the time of appearance varied somewhat from setting to setting. In gene

BL

bke, P. rhesus

.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

Aided by ex

one, and after the inhibition of the tendency to choose the first box at the left, the only definite tendency to appear was that of choosing the first box at the right, and then the one next to it. After one hundred and thirty trials, this method suddenly ga

etting, since the reader by carefully scanning the columns of data in table

y ratios of right to wrong first choices presented in the last column of table 5. Most of these irregularities were due, I have discovered,

he exhibited impulses to enter the box which would have been the correct one in the regular series of settings. He frequently inhibited such impulses and chose correctly, but at other times h

ular series of settings. Sobke seemed confused when he emerged from this box and had difficulty in locating the right one. Then followed direct correct choices for settings 3, 4, and 5. For setting 6, there is recorded a deliberately made wrong choice, and so on t

s no free idea of the relation of secondness from the right and is chiefly depen

tely First at Left

bke was merely fed in the apparatus according to previous description (p. 43). He exhib

ssed it was found possible and also desirable to increase the period of confinement, and in the end, sixty seconds proved satisfactory. It was also thought desirable to increase the number of trials per day from a single series during the early days to two or even three series from June 29 on. Often three series could be given in succession without difficulty. During the early trials on this problem Sobke worked remarkably well, but later his w

BL

bke, P. rhesus

| 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 | | |

Aided by ex

y, the choice of the second box from the right end. This proved surprisingly weak, in view of the animal's long tra

egree of success appear for the different settings. Thus, while settings 1, 2, 3, 6,

he solution of problem 3 (alternately the first box at

dequately solved than the second. This is not surprising when the nature of the two problems is considered, for whereas problem 2 requires choice by perception of the relationship of secondness from the right end of the group, problem 3 requires, instead, the choice of the end member of the group each time, with the ad

s extremely irregular; that for problem 3, figure 20, much more regular. Similarly, the daily ratios of right to

is reason and also because it did not seem feasible to have Sunday intervene between the final and perfect regular series and the control series, an additional regular series was given on July 19, in which, as the table indicates

ed similarly in one failure and nine successes. The choices were made easily and with

al. The fact seems to be that for this problem the particular setting is of relatively little importance; while turning alternately to the extreme left and the extreme right is of prime importance. That Sobke had the idea of alternation or of the end box, there seems no more reason

em 4.

ministered was the momentary lowering of the entrance door of the wrong box. As in the previous problem, he was aided after ten successive wrong choices. As might have been anticipated, he persistently entered the end boxes of the groups, and this in some instances probably would have been kept up for many minutes had not the experimenter lured him into the r

ht into the apparatus for the second series, he exhibited a wholly new form of behavior, for instead of attending diligently to the open doors and devoting his energies to trying to find the right box, he instead, after gazing at them for a few seconds, turned toward the experimenter and jumped for him savagely, throwing himself against the wire netting with great force. Th

ortunity to spring upon me. Previously, it had been possible for me to coax him into the apparatus by offering him food and to return him to his c

22 I gave Sobke an opportunity to enter the apparatus, he refused, and it was impossible to lure him in with food. Two hours later, having waited meantime for his breakfast, he entered readily and worked steadily and persistently through his third series of

total number of choices, and on July 23 correct reactions began to appear. Improvement during the next hundred trials was steady and fairly rapid, and on July 31, a record of seven right to thre

following day, August 3, unfortunately and contrary to the wishes of the experimenter, the laboratory was painted and there was necessarily considerable disturbance because of the presence of the workmen, and in addition, the pervasive odor of fresh paint. Sobke chose still less successfully on this date, and on August 4, he refused to work after the eighth trial. It is true that during t

BL

bke, P. rhesus

| | | | | | | | | | | | | | 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 | | | | | |

Aided by ex

e reward, but my best efforts, continuing up to August 28, failed markedly to improve the condition. The number of correct choices did somewhat

varied from 0 to confinement of sixty seconds, and many kinds of food in different amounts were tried as rewards, but in spite of everything Sobke failed to

ging conditions. It seems not improbable that had the work progressed without change in experimenter, or method of procedure, and above all without the disturbance of the painting, Sobke might ha

he number of open boxes was as great as five, as in settings 2 and 8, the task was obviously more difficult, but whereas success in setting 2 appeared early, in setting 8 it failed to appear during the course of experimentation. For the settings 3, 6, and 9, involving either seven or nine open boxes, the direct choice of the middle box was next to impossible, and Sobke tended to choose, first of all

s, Pongo

First at

ed with Skirrl and even with Sobke, he adapted himself to the multiple-choice apparatus very promptly, and only slight effort on the part of the observer was necessary to prepare him, by preliminary t

ius when again introduced to it gave no indications of fear, uneasiness, or dislike, but worked as formerly, making h

wer 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 different result from

SERIES

series 5th se

n. 20 min. 1

7 " 10 " 9 "

2 " 11 "

er unusual conditions worked steadily and well, whereas the monkeys, and e

the apparatus, this method naturally yielded success; whereas if the group included doors to the left of the middle, it resulted in failure. Obviously it was a most unsatisfactory method, and although it enabled him to

the first series of experiments. On April 26 it was increased to sixty seconds, in an effort to break him of the habit of choosing the "nearest" door. But he became extremely restless under the longer confinement and tried his best to raise the entrance and exit doors. Since there was at this time no mechanism for locking them when closed, it was difficult for the experimenter to prevent him from escaping by way

il 28, the two methods were again employed, the first in the initial series and the second in a final series of trials. The animal's persistent attempts to raise the doors gave the experimenter so much trouble that on April 29 b

e first choice was that of the right box and in that

ies, doors 1 to 4 occur as right doors; 5 to 9 do not. As punishment for wrong choices on this date, Julius was confined in the wrong box from one to five minutes. It was difficult to keep him in, but by means of cords which had been attached to the doors, this was succ

ber of correct first choices occurred, and on the last named date, Julius chose correctly only three times in his ten trials. At this time there was, as my notes record, no satisfactory indication of progress, and the status of the experiment seemed extremely unsatisfactory in as much as in spite of

BL

Orang utan

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 ----+------+-------+-------+-------+----

, that the successes were accidental, and it was anticipated that in a control series Julius would again make mistakes. But on the following day, May 12, the presentation of the original series of ten settings, which,

nearest to the starting point (sometimes the adjacent boxes were entered); (b) a tendency to avoid the "nearest" do

h a human subject, would undoubtedly be described as an ideational, and possibly even as a rational curve; for

atter of fact, for the solution he required about four times the number of trials which Sobke required and twice as many as were necessary for Skirrl. Were we to measure the intelligence of these three animals by the number of trials needed in problem 1, Sobke clearly would rank first, Skirrl second, and Julius last of all.

econd from t

a lever directly in front of him could fasten either one or both of the doors of a given box by a single movement. On May 13 Julius was given opportunity to obtain food from each of the boxes in turn, and trial of the locks was made in order to familiarize him with the new situation. He very quickly discov

eward. After the first trial in this series, in which Julius repeatedly entered the first box at the left, that is box 7, there was but slight tendency to re?nter the first box at the left of the group. Instead, Julius developed

rimenter could lower the door behind him. This he did only after having been punished for many wrong choices to the point of

nflamed and the lids nearly closed. Julius refused to eat, and experimentation was impossible. Until June 2 careful treatment and regulation of diet was necessary. He passed through

choices appeared, and Julius showed discouragement. Sawdust had been strewn on the floor, and in the intervals between trials as well as during confinement in wrong boxes, he took to playing with the sawdust. He would take it up in one hand and pour it from hand to

d the list will be more useful to the reader at this point than at the conclusion of the presentation of daily results. The following is not an ex

l the second from the right was reached. This method with irregularities and certain definite skippi

developed immediately after the orang utan's il

tendency (a) reappeared and p

the one next to it. In connection with this tendency, which of course required only two

animal returned to t

mplete circle so that the second box from the right was faced. This, the correct box, was often pr

d (right one), and then choice of some other box. This feint is peculiarly

e right end, Julius developed also the tendency to turn around in front of the box at the right

dency to take the one next in order or,

ithout approach to other boxes appe

nd the tendency to discouragement, both punishment and reward had to be altered from time to time, and other and more radical changes were occasionally made in th

RIMENT FROM DAY To

nishmen

ec. confinement ........

r 10 tria

c. confinement ........ F

each

.... Illness,

sec. confinement ........

each

" " ............. Foo

each

" " ............. Bee

on to

30 sec. confinement .. B

on to

c. confinement ........ B

on to

" " ............. Banan

fer

c. confinement ........

ri

finement in wrong box; Fo

d, return

point b

le

nfinement in wrong box; F

d, return

point b

le

punishment; allowed

oxes un

was

.... Return to

ve wrong

en box t

for 60

he boxes

leased

door an

e right

os

unishment .............

o starting point. .. Food o

unishment .............

... Same as on 2

. No punishment ...

to starting point ... Rew

oi

... Same as on J

unishment ............

starting point ... Reward on

.. Same as for Ju

onfinement in ..... Reward for

to starting point ..... Rew

confinement .......... Re

). 5 " " .......

.. 30 " " .......

to starting point ..... Rew

confinement .......... Re

.. 30 " " .......

.. 10 " " .......

by slight Reward in each right box raisi

o starting point ..... Rewa

..... " " " "

.. 10 to 60 sec. confinement ..

. Threatened with wh

s). " " " .....

10 sec. confinement

Threatened with whip

10 sec. confinement

.. 10 " " .......

Threatened with whi

region in which success was never obtained and to focus attention on the right, as contrasted with the wrong end of each group. It obviously contradicts the law of the gradual elimination of use less activities. In other words, it is wholly at variance with the principle of trial and error exhibited by many infrahuman organisms. Julius, although making many mistakes, wo

edict almost every choice. Indeed, to satisfy my curiosity in this matter during a number of series I guessed in advance the box which would be chosen. The percentages of correct guesses ranged from n

make it extremely difficult to obtain strictly comparable results from series to series and from day to day. The data for this problem, as

uently it happened that having used an inadequate method fairly persistently on a given day, the animal would on the following day exhibit a wholly different me

BL

Orang utan

| | | | | | | | {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.

Aided by ex

uliar and characteristic results. They differ from those previously obtained largely because of the orang utan's remarkably strong tendency to reenter the box through which he had just passed. This occurred so persistently, as may be seen in table 9 (June 17, second series, June 18, etc.), that a further modification of method was introduced in that after the same wrong box had been entered five times in s

in the use of this method, he developed the habit of rolling around from exit door to starting point by a series of somersaults. When especially discouraged he would often bump his head against the floor so hard that I could hear t

hoices per series increased from 0 to 8. But, as the observations were continued from day to day, it became more and more evident that the animal was merely passing from tendency to tendency-method to method-mixing tendencies, and occasionally developing new ones, without approach to the solution of the problem.

ncy developed and the method was used with increasing frequency. On June 30, it appeared in the first series, four times, in the second series, six times; on July 1, in the first series, three times, and in the second series, four times; on July 2, in the first series, five times, and in the second series, nin

right end of the group, would stop suddenly wherever he happened to be, turn toward his right in a complete circle, and hasten into the box nearest to him which, as often as not, proved to be the wrong one. Thus the idea of turning completely about, which had it continued its association with the idea of facing the first box at the right, wo

re appeared another tendency which possibly can be explained. Julius took to backing into the chosen box so that he could face the experimenter. He would then, after a period of hesitation, come out and promptly enter one of the other boxes. This tendency was apparently due to the fact that during one or two series the experimenter growled at the orang uta

proach to other boxes. But in the second series for July 10 there was an extraordinary improvement in method. This developed in the presence of two visitors, and it is therefo

factory, and the next it might seem equally clear that punishment by confinement for thirty seconds or sixty seconds, with reward for correct choice in every trial, yielded better results. In the end I had to admit that no best method had been demonstrated and that I had failed to develop conditions which

us and the series of trials, and stationed myself in one corner of the reaction-chamber with a whip in my hand. Whenever Julius entered a wrong box, I approached him with the whip and struck at him, being careful

consider it more satisfactory than the other procedures. I am now wholly convinced that Julius did his best

tered the right box. It was thought that this method might serve to break up the previously developed tendencies toward inadequate forms of response and so encourage the animal that he would later solve the problem when given opportunity to select the right box without aid from the experimenter. But as a matter of fact, while the ratio of right to

presented in figure 19. It is of course incomplete and it is of

First at t

ent and seemed to have exhausted his methods. It seemed wise instead of giving up work with him in the multiple-choice method to return to a form of problem 1. We may designate it as problem 1a. The right box is definable as

the large number of cases in which Julius chose first the second box from the right end of the series, or in other words that box which had been the right one in problem 2. Contrary to expectation, he showed no inclination

error. He had, it would seem, satisfied himself that the problem was insoluble. These results obtained in problem 1a constitute a most interesting comment on the effects of problem 2 on the orang utan. Behavior si

was the lack of consistent improvement. It seemed almost incredible that he should continue, day after day, to make incorrect choices in

BL

Orang utan i

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 |

Aided by ex

ersistently, and often vainly, to gain insight. He used ideas ineffectively. Animals far lower in intelligence (e.g., the pig), surpass him in ability to solve these relational problems because they use the method of elimination b

ated or discussed. They can be developed from later comparative studies of the data, for in th