MENTAL LIFE OF MONKEYS AND APES 41 



Problem 3. Alternately First at Left and First at Right 



Following the control series given in connection with problem 

 1, an interval of rest lasting from August 12 to August 19 was 

 allowed in order that Skirrl might in part at least lose the effects 

 of his training and regain his customary interest in the appa- 

 ratus by being allowed to obtain food easily instead of by dint 

 of hard labor, — labor which was harder by far, apparently, than 

 physical activity because it demanded of the animal certain 

 mental processes which were either lacking or but imperfectly 

 functional. The difficultness of the daily tasks appears to be 

 reliably indicated by the tendency to yawn. 



Systematic work on problem 3, which has been defined as 

 alternately the first door at the left and the first door at the 

 right of the group, was begun August 19, and for nine days a 

 single series of ten trials per day was given. Work then had 

 to cease because of the experimenter's return to Cambridge. 



The results of the work on this problem demand but brief 

 analysis and comment. The expected ratio of one right to four 

 wrong choices per series appears (see table 3) for the first series 

 of trials, and this in spite of the fact that Skirrl had been trained 

 for several weeks to choose the second door from the right end. One 

 would ordinarily have predicted a much larger number of in- 

 correct choices. The right choices were due to the monkey's 

 strong tendency to go first to the first door at the right and 

 thence to the one next to it. Indeed in the series given on August 

 24, this method was followed without variation. In other words, 

 in every one of the ten trials Skirrl entered first the box at the 

 extreme right end of the group. This necessarily resulted in 

 as many right as wrong first choices. Consequently, the ratio 

 reads 1 to 1. But the method was not adhered to, and at no 

 time either before or after that date did he succeed in equalling 

 this achievement. There was, as a matter of fact, no steady 

 improvement, and so far as one may judge from the records 

 which were obtained, the course of events in the solution of this 

 problem would have been similar to those in problem 2. 



