Six minutes after completion of the first control series, a second was given under slightly more favorable conditions, and in this only a single wrong choice occurred, in that box 2 was first chosen in trial 6 instead of box 1. From the results of these two control series, it 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 involving an idea of the relation of the right box to the other members of the group would be difficult to decide. I hesitate to infer definite ideation from the available evidence, but I strongly suspect the presence of images and 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 the experimental procedure and progressed more steadily toward the solution of the problem 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 regular; the second, that for Skirrl, is quite as surprisingly irregular. These results correlate perfectly with the steadiness and predictability of the former's responses and the irregularity 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 to health and training, for experimental work. He had come to work quietly, fairly deliberately, and very steadily. His timidity had diminished and he would readily come to the experimenter for food, although still he was somewhat distrustful at times and became timid when anything unusual occurred in the apparatus.

As preparation for problem 2, a break in regular experimentation covering four days followed the control series of problem 1. On each of these 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 all other doors closed. For this feeding experiment, the doors were opened in irregular order, and this order was changed from day to day.

Systematic work with problem 2 began on May 3, with punishment of thirty seconds for mistakes and a liberal reward of food for each success. Early in the series of trials it was discovered that Sobke was likely to become discouraged and waste a great deal of time unless certain aid were given by the experimenter. On this account, after the first two trials, the method was adopted of punishing the animal by confinement for the first ten mistakes 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, the work might have been continued successfully with a smaller number of trials than ten per day. But under the circumstances it seemed wiser to avoid the risk of discouraging and thus spoiling the animal for use in the experiment. It should be stated, also, that it proved impossible to adhere to the period of thirty seconds as punishment in this series. For the majority of the wrong choices confinement of not more than ten seconds was used.

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

The work on May 6 was distinctly better, and the animal's behavior indicated, in a number of trials, definite recognition of the right door. He might, for example, make a number of incorrect choices, then pause for a few seconds to look steadily at the doors, and having apparently found some cue, run directly to the right box. No aid from the experimenter was needed in this series.

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

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

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

Work was continued thus steadily until May 28 when, because of the failure of the animal to improve, it seemed wise to increase the period of confinement as punishment to sixty seconds. In the meantime, it had sometimes been evident that Sobke was near to the solution of his problem. He would often make correct choices in three or four trials in succession and then apparently lose his cue and fail utterly for a number of trials.

After June 1, in order to hasten the solution of the problem, two series per day were given. In some instances the second series was given almost immediately after the first, while in others an interval of an hour or more intervened. It was further found desirable to give Sobke all of his 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 given. Thus, the eagerness of the monkey to locate the right box was increased and, as a matter of observation, his deliberateness and care in choice increased correspondingly. Sixty seconds punishment was found satisfactory, and it was therefore continued throughout the work on this problem.

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

An analysis of the data of table 5 reveals five methods or reactive tendencies which appeared more or less definitely in the following order: (a) Choice of first box at the left, because of experience in problem 1. This tendency was very quickly suppressed by the requirements in connection with problem 2. Indeed one of the most significant differences which I have discovered between the behavior of the primates and that of other mammals is the time required for the suppression of such an acquired tendency. The monkey seems to learn almost immediately that it is not worth while to persist 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 4 would be chosen first, then box 3. Or, if this did not occur, the method previously described under (b) was likely to be employed, as for example, in setting 8, where such choices as 7.6.5.1.8 appear. (d) In certain series there appeared a marked preference for a particular box, usually box 3 (see results for May 24). This was doubtless due in a measure, if not wholly, to the fact that box 3 was the right box twice in each series of ten settings. But it should be added that the same is true 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 roughly appeared in the order named, but there were certain irregularities and the order as well as the time of appearance varied somewhat from setting to setting. In general, method c was the most frequently used prior to the 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 very easy for Sobke; others, extremely difficult. Consequently, the number of methods which were tried and rejected for a given setting varies from two to five. Setting 2 proved a fairly simple 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 gave place to direct choice of the right box, and during the following twenty-eight series, no error occurred for this setting. Setting 4, on the contrary, proved extremely difficult, and a variety of methods is more or less definitely indicated by the records.

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

Sobke's curve of learning (figure 19) in problem 2, is extremely irregular, as was that of Skirrl. Similar irregularities appear in the daily ratios of right to wrong first choices presented in the last column of table 5. Most of these irregularities were due, I have discovered, to unfavorable external conditions. Thus, dark rainy days and disturbing noises outside the laboratory were obviously conditions of poor work.

On the day following the final and correct series for problem 2, a control series was given. In this Sobke seemed greatly surprised by the new situations which presented themselves. Repeatedly 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 he reacted quickly and made mistakes. It was evident from his behavior that he was not guided by anything like a definite idea of the relation of the right box to the other 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 correct choice was made with deliberation. For the second setting, box 3 was immediately chosen, as should have been the case in the regular 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 throughout the series, the choices being characterized by deliberateness and definite search for the right box. Uncertainty was plainly indicated, and in this the behavior of the animal differed markedly from that in the concluding series of the regular experiment.

It seems safe to conclude from the results of these control series that Sobke has no free idea of the relation of secondness from the right and is chiefly dependent upon memory of the particular settings for cues which lead to correct choice.

Problem 3. Alternately First at Left and First at Right

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

The method of experimentation chosen for problem 3 in the light of previous experience was that of confining the monkey for a short time, ten to fifteen seconds, in the wrong box, in each of the first ten mistakes for a given trial, and of then aiding him to find the right box by the slight and momentary raising of the exit door. Aid proved necessary in a few of the trials during the first four days. Then he worked independently. As work progressed 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 willingness diminished, evidently because of his failure readily to solve the problem, and it became extremely difficult to coax him into the apparatus. On days when he entered only reluctantly and as it seemed against his will, he was likely to be nervous, erratic, and often slow in making his choices, but above all he tended to waste time by not returning to the starting point, preferring rather to loiter in the alleyways 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 pronounced reactive tendencies: (a) As the initial tendency, the choice of the second box from the right end. This proved surprisingly weak, in view of the 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 and in 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.



From the first this problem promised to be much easier for Sobke than problem 2, and although the actual number of trials necessary for the solution is greater by sixty for problem 3 than for problem 2, comparison of the data of the tables justifies the statement that the third problem was both easier and more nearly adequately 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 additional variation of alternation of ends. Now as it happens, the end member is easily selected by the monkey, and it appears further that alternation was relatively easy for Sobke to acquire. Consequently, the combination of end and alternation proved easier than the choice of the second from the right end of the group.

The above statements are supported by comparison of the curves of learning. The curve for problem 2, figure 19, is extremely irregular; that for problem 3, figure 20, much more regular. Similarly, the daily ratios of right to wrong choices as exhibited in tables 5 and 6 indicate smaller 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 of good luck than good management that he succeeded in presenting this perfect series: For this 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, a single mistake occurred, in trial 5. The monkey was working perfectly. The series of trials required only ten minutes, and it was evident that carelessness and eagerness to obtain food were chiefly responsible for the mistake.

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

This excellent showing for the control series wholly justifies the comparison of problems 2 and 3 as to difficultness, made above. Whereas in both problems 1 and 2 the control trials caused confusion, in the case of problem 3, they did not essentially alter the behavior of the animal. 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 for insisting than that he had the idea of secondness from the right end in problem 2. It is possible, even probable, that these ideas existed rather vaguely in his consciousness, but there is obviously no necessity for insisting that the solution of the problems depended upon them.

Problem 4. Middle

As the available time for the continuation of the experiment was limited, it was decided to proceed with work on problem 4 immediately upon the completion of problem 3, and on July 20, the problem of the middle door was presented to Sobke. Since it was anticipated that this sudden change would confuse and discourage him greatly, the only form of punishment administered 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 right box by slightly raising the exit door. 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 number of choices, eighty-eight. In the second series, he was aided in four of the trials. The total time required was seventy-two minutes, and the total number of choices was seventy-six.

Throughout the first series, Sobke worked hard, but with evidently increasing dissatisfaction. He clung persistently to his acquired tendency to choose the end boxes, and after each trial he returned less willingly to the starting point. Up to this time his attitude toward the experimenter had been perfectly friendly, if not wholly trustful. But when on July 21 he was brought 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. This was repeated a number of times during the first two or three trials, and it occurred less frequently later in the series. Since nothing unusual had happened outside of the experiment room, the suggested explanation of this sudden change in attitude and behavior is that the monkey resented and blamed on the experimenter the difficulty which he was having in obtaining food.

From this time on until the end of my work, Sobke was always savage and both in and out of the apparatus he was constantly on the watch for an opportunity 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 cage by walking after him. But on and after the twenty-first of July, it was impossible for me to approach him without extreme risk of being bitten.

Doctor Hamilton when told of this behavior, reported that several times monkeys have shown resentment toward him when they were having trouble in the experiment. I therefore feel fairly confident that I have not misinterpreted Sobke's behavior. When on July 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 trials, but in no one of these trials did he choose correctly. Neither on this day nor the following did he exhibit resentment while at work. He apparently had regained his affective poise and was able to attend as formerly to the task of locating his rewards.

During these first three series, although the ratio of right to wrong choices stood 0 to 10, there occurred a marked reduction in the number of trials in which aid was necessary as well as in the 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 three wrong trials was obtained. This was surprising to the experimenter, as well as gratifying, since he was eager to have the animal complete this problem before work should have to be discontinued.

Everything went smoothly until August 2, when my assistant, who had been left in charge of the experimental work for a week, attempted to increase the number of trials per day to two series. Sobke apparently was not quite ready for this increase in the amount of his day's labor and refused to work at the end of the first series. In this series he did less well than on the previous day. The 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 these bad days the total number of choices steadily diminished while the successes, also, diminished, or at best, failed to increase. When on August 9, I returned to the laboratory to take charge, I found that Sobke was no longer trying to solve the problem as when I had gone away. His attitude had changed in that he had become 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 the number of trials and the punishment, and by increasing the value of the reward, but my best efforts, continuing up to August 28, failed markedly to improve the condition. The number of correct choices did somewhat increase, but at no time did the animal attain the degree of success which he had achieved as early as July 31 in the eleventh series of trials.

During the last two weeks of experimentation, all possible efforts were put forth to discover the best combination of rewards and punishments. Punishment was 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 improve markedly. From time to time, notably on August 12 and 21, he exhibited peculiarly strong resentment toward me and repeatedly attempted to attack me.

The outcome of my experiments with problem 4 is peculiarly interesting in that it indicates the importance of a favorable attitude toward the work and the extreme risk from disturbing or discouraging 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 have solved problem 4 within a few days. This is by no means certain, however, for in problems 2 and 3 the ratio of right to wrong choices instead of increasing steadily increased very irregularly.

The detailed results for this problem are given in table 7. Reactive tendencies which appear are: (a) persistent choice of the end boxes followed, subsequently, by (b) the tendency to locate the middle box directly. This proved fairly easy when the number of boxes involved was only three as in settings 1, 4, 7, and 10. Setting 4 was most difficult of all, because box 9 was avoided or ignored. When the 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, a particular box toward one end of the series, for example, box 2, in setting 3, and box 7 in setting 9. To the experimenter, as he watched the animal's behavior, it looked as though effort each time were being made to locate the middle member of the group. This appeared relatively easy for groups of three boxes, extremely difficult for as many as five boxes, and almost 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 the experimenter throughout the period of investigation. He at no time showed inclination to bite and could be handled safely. As contrasted 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 trials, for the regular experiments. But in order to facilitate work, he was familiarized with the apparatus by means of regular route training and feeding in the several boxes from April 5 to April 9.

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

The regular experimentation was undertaken on April 13, and the results of the first series of trials with Julius are sharply contrasted with those 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 different result from that obtained with the monkeys is indicated below in the total time required for a series of trials. As examples, the data for the first, second, fifth, and tenth series are presented.



TIME FOR SERIES OF TRIALS

1st series 2nd series 5th series 10th series Skirrl 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 under other unusual conditions worked steadily and well, whereas the monkeys, and especially Sobke, tended to be distracted and often refused to work at all.

Almost from the beginning of his work on problem l, Julius began to develop the tendency to enter immediately the open door nearest the starting point. In case the group of open doors lay to the right of the middle of 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 make more right than wrong first choices, it prevented him from increasing the number of right choices, and as table 1 indicates, it maintained the ratio of 1 right to .67 wrong first choices for eight successive days.

On April 23 a break occurred in which the number of correct choices was reduced from six to five. Julius worked very rapidly and with almost no hesitation in choosing. My notes record "he seems to miss the point wholly. It is doubtful whether the punishment is sufficiently severe." At this time he was being punished by thirty seconds confinement in each wrong box, the interval having been held fairly steadily from 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 of the entrance door or from raising the exit door sufficiently to obtain the food. Indeed, the longer confinement worked so unsatisfactorily that on the following day I substituted for it the punishment of forcing him to raise the entrance door of the wrong box in order to escape for a new choice. He was rewarded with food in the alleyway H, beside door 15 (figure 17), only when 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 the former method, and he was rewarded with food whenever he found the right box. But on April 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 barbed wire was nailed over the windows of the entrance doors with the hope that it might prevent him from working at them. But he quickly learned to place his fingers between the barbs and raise the doors as effectively as ever.

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

As it seemed absolutely essential to break the unprofitable habit of choosing the nearest door, on May 3 a new series of settings was presented, in which only the doors to the left of the middle of the row of 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 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 successfully accomplished. Yet another and slightly different series of settings was employed on May 4, and this, proving satisfactory, was continued in use until the end of the experiment, with punishment ranging from sixty to one hundred and twenty seconds for each mistake.

Naturally the modification of settings introduced May 3 greatly increased the proportion of wrong first choices. Indeed, as appears in table 8, the ratio of right to wrong immediately changed from 1:0.67 to 1:4.00. Between May 3 and May 10, no steady and consistent improvement in method or in the number 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 the experimenter's best efforts to break up the habit of choosing the nearest door, the orang utan still persisted, to a considerable extent, in the use of this method. The only encouraging feature of the results was an evident tendency to choose somewhat nearer the left end of a group than previously.



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 the surprise of the experimenter, for no indication had previously appeared of this approaching solution of the problem. It seemed possible, however, 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, of course, differed radically from the settings used from May 4 to May 11 was responded to promptly, readily, and without a single mistake. Julius had solved his problem suddenly and, in all probability, ideationally.

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

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

Never before has a curve of learning like this been obtained from an infrahuman animal. I feel wholly justified in concluding from the evidences at hand, which have been presented as adequately as is possible without going into minutely detailed description, that the orang utan solved this simple problem ideationally. As a matter 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. But other facts clearly indicate that Julius is far superior to the monkeys in intelligence. We therefore must conclude that where very different methods of learning appear, the number of trials is not a safe criterion of intelligence. The importance of this conclusion for comparative and genetic psychology needs 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 of training was not necessary to keep him in good form. During this rest interval, locks were attached to the doors of the apparatus so that the experimenter by moving 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 discovered that the doors could 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 well as 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 which day a single series was given. The period of punishment adopted was twenty seconds, and for each successful choice a small piece of banana was given as a reward. 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 reenter the first box at the left of the group. Instead, Julius developed the method of moving box by box toward the right end of the group. The choices were made promptly, and their systematic character enabled the animal to obtain his reward fairly quickly, in spite of the large number of mistakes.

In the second series, the orang utan developed the interesting trick of quickly dodging out of the wrong box before the experimenter could lower the door behind him. This he did only after having been punished for many wrong choices to the point of discouragement. The trick was easily broken up by the sudden lowering of the entrance door as soon as he had passed under it.

There appeared on May 21 an unfavorable physical condition which manifested itself, first of all through the eyes which appeared dull and bloodshot. On the following day they were inflamed 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 what at the time seemed a rather startling condition, but rapidly regained his usual good health, and on June 3, although somewhat weak and listless, he again worked fairly steadily.

Since it was now possible to lock the doors and confine the animal for any desired period, on June 5 the interval of punishment was made sixty seconds, and a liberal quantity of banana, beet, or carrot was offered as reward. No increase in the number of successful 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 hand until all had slipped through his fingers, then he would scrape together another handful and go through the same process. Often he became so intent on this form of amusement that even when the exit door was raised, he would not immediately go to get the food.

The reactive tendencies which appeared in the work on problem 2 will now be 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 the conclusion of the presentation of daily results. The following is not an exhaustive list but includes only the most important and conspicuous tendencies or methods together with the dates on which they were most apparent.

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

(b) June 3, preference for number 3 and number 4 developed immediately after the orang utan's illness and when he was working rather listlessly.

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

(c) June 14, a tendency to choose the box at or near the right end of a group, and then the one next to it. In connection with this tendency, which of course required only two choices in any given trial, interest in 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 before it, and turning through a complete circle so that the second box from the right was faced. This, the correct box, was often promptly entered. This method, if persisted in, would obviously have yielded solution of the problem.

(e) July 5, approach to and pretense to enter the box next to the right end (right one), and then choice of some other box. This feint is peculiarly interesting, and its origin and persistence are difficult to account for.

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

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

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

For this problem, it proved impossible to establish and maintain uniform conditions of experimentation. Instead, because of the failure of the animal to improve and 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 the experimental procedure. Below for the sake of condensed and consecutive presentation, the most important 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 mind we may continue our description of results. On June 9 there developed a tendency to increase the magnitude of the original error by choosing nearer the left end of the groups. This is odd, since one would naturally suppose that an animal as intelligent as the orang utan would tend to avoid the general 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, worked diligently and, for the most part, fairly rapidly. The day's work proved most important because of the change in method and also because of the appearance of hesitation, the rejection of certain boxes, and the definite choice of others. My notes record "this is a most important day for Julius in problem 2;" but subsequent results do not clearly justify this prophecy.

The method of choosing the first box at the left and then of moving down the line until the right one was reached was so consistently followed that during a number of days it was possible for me to predict 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 ninety to one hundred. June 10, for example, yielded two series for which the ratio of right to wrong first choices was 0 to 10, and in which the method described above was used consistently throughout.

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

It was occasionally noted that the disintegration of a definite method and the disappearance of the tendency on which it depended occurred rather suddenly. Frequently 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 method. Even over night a new method might develop. In the monkeys, although there was occasionally something 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 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