The Mental Life of Monkeys and Apes: A Study of Ideational Behavior. Robert Mearns Yerkes
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 constitute a series. The summary for this series indicates three right and seven wrong first choices, that is, three cases in which the right box was entered first. The ratio of right to wrong first choices is therefore 1 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.