64 ROBERT M. YERKES ' 



It is also noteworthy that JuUus in the presence of visitors 

 or under other unusual conditions worked steadily and well, 

 whereas the monkeys, and especially Sobke, tended to be dis- 

 tracted and often refused to work at all. 



Almost from the beginning of his work on problem 1, Julius 

 began to develop the tendency to enter immediately the open 

 door nearest the starting point. In case the group of open 

 doors lay to the right of the middle of the apparatus, this method 

 naturally yielded success; whereas if the group included doors 

 to the left of the middle, it resulted in failure. Obviously it 

 was a most unsatisfactory method, and although it enabled him 

 to make more right than wrong first choices, it prevented him 

 from increasing the number of right choices, and as table 1 

 indicates, it , maintained the ratio of 1 right to .67' wrong first 

 choices for eight successive days. 



On April 23 a break occurred in which the number of correct 

 choices was reduced from six to five. Julius worked very rapidly 

 and with almost no hesitation in choosing. My notes record 

 "he seems to miss "the point wholly. It is doubtful whether 

 the punishment is sufi&ciently severe." At this time he was 

 being punished by thirty seconds confinement in each wrong 

 box, the interval having been held fairly steadily from the first 

 series of experiments. On April 26 it was increased to sixty 

 seconds, in an effort to break him of the habit of choosing the 

 " nearest " door. But he became extremely restless under the 

 longer confinement and tried his best to raise the entrance and 

 exit doors. Since there was at this time no mechanism for 

 locking them when closed, it was difficult for the experimenter 

 to prevent him from escaping by way of the entrance door or 

 from raising the exit door sufficiently to obtain the food. In- 

 deed, the longer confinement worked so unsatisfactorily that on 

 the following day I substituted for it the punishment of forcing 

 him to raise the entrance door of the wrong box in order to escape 

 for a new choice. He was rewarded with food in the alleyway 

 H, beside door IS (figure 17), only when he chose correctly on 

 first attempt. 



This method discouraged him extremely and proved wasteful 

 of time. Consequently, in a second series on the same date 

 return was made to the former method, and he was rewarded 

 with food whenever he found the right box. But on April 28, 



