Chapter III: Results of Multiple-Choice Experiments (3)

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