The Mental Life Of Monkeys And Apes Part 2

Settings for Control Experiments

PROBLEM 1. First at left end

Doors No. of No. of Settings open doors open right door 1..................2.3.4......................3..................2 2..................6.7.8.9....................4..................6 3..................3.4.5......................3..................3 4..................4.5.6.7.8.9................6..................4 5..................6.7.8.9....................4..................6 6..................1.2.3.4.5..................5..................1 7..................2.3.4.5.6.7.8..............7..................2 8..................3.4.5.6.7.8................6..................3 9..................5.6.7......................3..................5 10..................1.2.3.4.5.6.7.8.9..........9..................1

PROBLEM 2. Second from right end

Doors No. of No. of Settings open doors open right door 1..................5.6.7.8....................4..................7 2..................2.3.4.5.6..................5..................5 3..................1.2.3.4.5.6.7.8.9..........9..................8 4..................5.6.7......................3..................6 5..................1.2.3.4....................4..................3 6..................4.5.6......................3..................5 7..................2.3.4.5....................4..................4 8..................1.2.3......................3..................2 9..................1.2.3.4.5.6.7..............7..................6 10..................2.3.4.5.6.7.8.9............8..................8

PROBLEM 3. Alternate left and right ends

Doors No. of No. of Settings open doors open right door 1..................5.6........................2..................5 2..................5.6........................2..................6 3..................4.5.6.7.8.9................6..................4 4..................4.5.6.7.8.9................6..................9 5..................1.2.3.4.5..................5..................1 6..................1.2.3.4.5..................5..................5 7..................2.3.4.5.6.7................6..................2 8..................2.3.4.5.6.7................6..................7 9..................3.4.5.6.7.8................6..................3 10..................3.4.5.6.7.8................6..................8

PROBLEM 4. Middle

Doors No. of No. of Settings open doors open right door 1..................4.5.6.7.8..................5..................6 2..................1.2.3......................3..................2 3..................1.2.3.4.5.6.7.8.9..........9..................5 4..................2.3.4.5.6..................5..................4 5..................6.7.8......................3..................7 6..................3.4.5.6.7.8.9..............7..................6 7..................7.8.9......................3..................8 8..................1.2.3.4.5.6.7..............7..................4 9..................2.3.4......................3..................3 10..................3.4.5.6.7..................5..................5

It was my aim so far as possible to present to a given subject each day the ten settings under a given problem in order, without interruption.

If for any reason the series of observations had to be interrupted, it was resumed at the same point subsequently. Occasionally it was found desirable or necessary to present only five of the series of ten settings in succession and then to interrupt observations for an interval of a few minutes or even several hours. But as a rule it was possible to present the series of ten settings. All things being considered, it proved more satisfactory to give only ten trials a day to each subject. Frequently twenty and rarely thirty trials were given on the same day. In such cases the series of settings was simply repeated.

The only pause between trials was that necessary for resetting the entrance doors and replenishing the food which served as a reward for success.

III

RESULTS OF MULTIPLE-CHOICE EXPERIMENTS

1. Skirrl, _Pithecus irus_

_Problem 1. First at the Left End_

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

Skirrl had previously been used by Doctor Hamilton in an experimental study of reactive tendencies. He proved so remarkably inefficient in the work that Doctor Hamilton was led to characterize him as feeble-minded, and to recommend him to me for further study because of his mental peculiarities. With me he was from the first frank, aggressive, and inclined to be savage. It was soon possible for me to go into the large cage, Z, with him and allow him to take food from my hand. He was without fear of the experimental apparatus and it proved relatively easy to accustom him to the routine of the experiment. Throughout the work he was rather slow, inattentive, and erratic.

Beginning on April 7, I sought to acquaint him with the multiple-choice apparatus by allowing him to make trips through the several boxes, with the reward of food each time. Thus, for example, with the entrance and exit doors of box 7 raised, the monkey was allowed to pa.s.s into the reaction-compartment E and thence through box 7 to the food cup. As soon as he had finished eating, he was called back to D by the experimenter and, after a few seconds, allowed, similarly, to make a trip by way of one of the other boxes. By reason of this preliminary training he soon came to seek eagerly for the reward of food.

On April 10 the apparatus was painted white in order to increase the lightness and thus render it easier for the experimenter to observe the animal's movements, and when on April 12 Skirrl was again introduced to it for further preliminary training, he utterly refused to enter the boxes, giving every indication of extreme fear of the white floors and even of the sides of the boxes. Finally, the attempts to induce him to enter the boxes had to be given up, and he was returned to his cage unfed. The following day I was equally unsuccessful in either driving or tempting him with food into the apparatus. But on April 14 he was so hungry that he was finally lured in by the use of food. He cautiously approached the boxes and attempted to climb through on the sides instead of walking on the floor. It was perfectly evident that he had an instinctive or an acquired fear of the white surfaces. As the matter was of prime importance for the success of my work, I inquired of Doctor Hamilton, and of the men in charge of the cages, for any incident which might account for this peculiar behavior, and I learned that some three months earlier, while the animal cages were being whitewashed, Skirrl had jumped at one of the laborers who was applying a brush to the framework of one of the cages and had shaken some lime into his eyes. He was greatly frightened and enraged. Evidently he experienced extreme discomfort, if not acute pain, and there resulted an a.s.sociation with whiteness which was quite sufficient to cause him to avoid the freshly painted apparatus.

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

On the morning of April 19, Skirrl was introduced to the apparatus and given his first series of ten trials on problem 1. This problem demanded the selection of the first door at the left in any group of open doors.

The procedure was as previously described in that the experimenter raised the entrance doors of a certain group of boxes, admitted the animal to the reaction-chamber, punished incorrect choices by confining the animal for thirty seconds, and rewarded correct choices by raising the exit door and thus permitting escape and the obtaining of food. The trials were given in rapid succession, and the total time required for this first series of ten trials was thirty-five minutes. Skirrl worked faithfully throughout this interval and exhibited no marked discouragement. When confined in a box he showed uneasiness and dissatisfaction by moving about constantly, shaking the doors, and trying to raise them in order to escape.

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

As it is highly important, not only in connection with the present description of behavior, but also for subsequent comparison of the reactions of different types of organism in this experiment, to present the detailed records for each trial, tables have been constructed which offer in brief s.p.a.ce the essential data for every trial in connection with a given problem.

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

Taking the first line of table 1 below the explanatory headings, we note on April 19 ten trials, numbered 1 to 10, were given to Skirrl. In trial 1, with setting 1, he chose correctly the first time, and the record is therefore simply 1. In trial 2, setting 2, he incorrectly chose box 9, the first time. At his next opportunity, he chose box 8, which was the right one. The record therefore reads 9.8. In trial 3, setting 3, he chose incorrectly twice before finally selecting the right box. The record reads 6.7.3, and so on throughout the ten trials which const.i.tute a series. The summary for this series indicates three right and seven wrong first choices, that is, three cases in which the right box was entered first. The ratio of right to wrong first choices is therefore 1 to 2.33. Since the total number of doors open in the ten settings is thirty-five, and since in each of the ten settings one door is describable as the right door, the probable ratio, apart from the effects of training, of right to wrong first choices is 1 to 2.50. It is evident, therefore, that Skirrl in his first series of trials closely approximated expectation in the number of mistakes.

TABLE 1

Results for Skirrl, _P. irus_, in Problem 1

========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== No. S.1 S.2 S.3 S.4 S.5 S.6 S.7 S.8 S.9 S.10 Ratio Date of R W of trials 1.2.3 8.9 3.4.5.6.7 7.8.9 2.3.4.5.6 6.7.8 5.6.7 4.5.6.7.8 7.8.9 1.2.3 R to W --------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- April 19 1- 10 1 9.8 6.7.3 9.7 6.2 7.8.6 {6.7.7.7 4 7 2.3.3.1 3 7 1:2.33 {6.5 20 11- 20 3.2.1 9.8 5.3 7 4.2 8.8.6 5 8.4 7 3.1 3 7 1:2.33 21 21- 30 3.1 8 3 8.7 6.2 6 5 6.4 9.7 1 5 5 1:1.00 22 31- 40 1 9.8 3 7 6.2 6 6.7.5 5.8.4 9.8.9.8.7 2.1 4 6 1:1.50 23 41- 50 2.3.1 8 5.7.3 7 4.2 6 5 7.8.4 7 3.1 5 5 1:1.00 24 51- 60 1 8 4.5.7.3 9.7 5.6.2 6 6.7.5 6.4 8.9.7 1 4 6 1:1.50 26 61- 70 1 8 6.7.4.7.3 7 4.5.6.2 6 5 8.4 7 3.2.3.1 6 4 1: .67 27 71- 80 3.1 8 3 9.7 4.6.2 7.6 6.5 5.8.4 7 1 4 6 1:1.50 28 81- 90 2.3.1 8 3 7 4.5.6.2 6 5 5.8.4 7 1 7 3 1: .43 29 91- 100 1 8 3 9.7 6.2 6 5 4 7 1 8 2 1: .25 30 101- 110 1 8 4.3 7 5.6.2 6 5 4 7 2.3.1 7 3 1: .43 May 1 111- 120 2.3.2.1 8 3 7 2 6 5 4 7 1 9 1 1: .11 3 121- 130 1 8 5.6.3 7 4.5.2 6 5 4 7 1 8 2 1: .25 4 and 5 131- 140 3.2.1 8[1] 3 7 2 6 5 4 7 1 9 1 1: .11 5 141- 150 1 8 4.3 7 2 6 5 4 7 1 9 1 1: .11 --------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- 2.3.4.5 1.2.3.4.5 2.3.4 6.7.8.9 3.4.5 4.5.6.7.8.9 6.7.8.9 1.2.3.4.5 6.7.8 3.4.5.6.7.8 5.6.7 6.7.8.9 +---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- 6 1- 10 2 6 3 4 6 3.2.1 6.2 5.6.7.8.3 5 6.1 6 4 1: .67 ========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+========

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

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

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

During the first week of work on this problem, Skirrl improved markedly.

His performance was somewhat irregular and unpredictable, but on the whole the experiment seemed fairly satisfactory. Cold, cloudy, or rainy days tended to diminish steadiness and to increase the number of mistakes. Similarly, absence of hunger was unfavorable to continuous effort to find the right box.

The period of confinement, as punishment for wrong choices, was increased from thirty seconds to sixty seconds on April 26. But there is no satisfactory evidence that this favored the solution of the problem.

Work on May 4 was interrupted by a severe storm, the noise of which so distracted the monkey that he ceased to work. Consequently, observations were interrupted on the completion of trial 132, and on May 5, the series was begun with setting 3. On this date, eighteen trials were given in succession, and in only one of them did a mistake occur. Since the ten trials numbered 133 to 142 were correct, Skirrl was considered to have solved problem 1, and systematic training was discontinued.

On the following day, as a measure of the extent to which the animal had learned to select the first door at the left no matter what its position or the number of doors in the group presented, a control series was given in which the settings differed from the regular series of settings. These supplementary settings are presented at the bottom of table 1 together with the records of reaction in ten trials.

Since in only six of these ten control settings was the first choice correct, it is scarcely fair to insist that the animal was reacting on the basis of an ideational solution of the problem. Rather, it would seem that he had learned to react to particular settings. A careful study of all of the data of response, together with notes on the varied behavior of the animal during the experiments, justifies the statement that Skirrl's solution of problem 1 was incomplete and unreliable. It was highly dependent upon the particular situation, or even the particular door at the left end of the group, and slightly if at all dependent upon anything comparable to the human idea of first at the left of the group.

This particular series of observations has been described and discussed in some detail in order to make the chief points of method clear. It will be needless, hereafter, to refer explicitly to many of the characteristics of reaction or to the important points in the construction of tables which have been mentioned.

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

Unquestionably, the form of such a curve of learning should be considered in connection with the method or methods of selecting the right box employed by the animal during the course of experimentation.

It appears from an a.n.a.lysis of the behavior of Skirrl in problem 1 that there developed a single definite and persistent method, namely, that of going to one box in the group, and in case it happened to be a wrong one, of choosing, on emergence from it, the next toward the right end of the group, and so on down the line. Having reached the extreme right end, the tendency was to follow the side of the reaction-chamber around to the opposite end and to enter the first box at the left end of the group, which was, of course, the right one. This method appears, with certain slight variations, in approximately ninety per cent of the trials which involved incorrect choices. Thus, in the case of trials 121 to 130, of which eight exhibit right first choices, the remaining two exhibit the method described above except that the final member at the right end of the group was in each case omitted.

[Ill.u.s.tration: FIGURE 18.--Error curves of learning for the solution of problem 1 (first box at left end).]

On the whole, Skirrl's behavior in connection with this problem appears to indicate a low order of intelligence. He persisted in such stupid acts as that of turning, after emergence from the right box, toward the right and pa.s.sing into the blind alley I, instead of toward the left, through G and H, to D. In contrast with the other animals, he spent much time before the closed doors of the boxes, instead of going directly to the open doors, some one of which marked the box in which the reward of food could be obtained. It is, moreover, obvious that his responses, as they appear in table 1, are extremely different from those of a human being who is capable of bringing the idea of first at the left end to bear upon the problem in question.

_Problem 2. Second from the Right End_