198 ROBERT. M. YERKES AND CHARLES A. COBURN 



PROBLEM 2 



For this problem, which is definable as the second mechanism 

 from the subject's left, all of the data for discussion will be 

 found in tables 3, 4, and 5. Again, as in the case of problem 1, 

 the regular series consisted, throughout the training, of five 

 trials, but as many as six such series were given on a single 

 day. Bracketed series appearing, for example, in table 5, under 

 the dates June 23, 24, 25, and 28 and July 1, 2, 3 and 4, were 

 continuous, that is, ten trials were given in succession instead 

 of only five. 



For the ten settings of problem 2, the total number of open 

 doors is fifty, and the expectation therefore is that prior to 

 experience an animal will choose correctly once in five times, 

 thus giving a ratio of right to wrong choices of 1 to 4. That 

 this expected ratio does not appear on the first day of experimen- 

 tation is due to the effect of the previous training in problem 1. 

 The tendency to enter the first box at the left was persistent 

 in both subjects and often that box was re-entered a number of 

 times in spite of punishment. In tables 3 and 4 the data for 

 these statements are presented, and in table 5 it may be noted 

 that on the first day of work on problem 2 neither subject made 

 a single correct first choice. 



The ratio of correct to incorrect first choices for the female 

 rapidly, although somewhat irregularly, decreased with experi- 

 ence until on July 4th it stood 1 to .19. On this date she suc- 

 ceeded in choosing correctly in ten successive trials, and was 

 therefore considered to have solved the problem perfectly. 



Similarly, the ratio for the male changed fairly rapidly until 

 on July 11th it stood 1 to .11. At this time, although he had 

 not succeeded in choosing correctly in each of the ten settings 

 consecutively, his training was discontinued, for he had already 

 delayed experimentation with the female for a week, and it 

 was perfectly clear that although he made an occasional error, 

 he was capable of perfectly solving the problem. 



Whereas the female finished this problem as a result of 390 

 trials, the male had made only nine out of ten correct choices 

 at the end of 520 trials, when his training was discontinued. 

 We are inclined to think that this is a reliable indication of the 

 difference in docility between these two individuals. 



