MENTAL LIFE OF MONKEYS AND APES 57 



tremely 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 inter- 

 vene 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 essen- 

 tially 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, 



