58 ROBERT M. YERKES 



the problem of the middle door was presented to Sobke. Since 

 it was anticipated tha;t this sudden change would confuse and 

 discourage him greatly, the only form of punishment admin- 

 istered was the momentary lowering of the entrance door of 

 the wrong box. As in the previous problem, he was aided after 

 ten successive wrong choices. As might have been anticipated, 

 he persistently entered the end boxes of the groups, and this 

 in some instances probably would have been kept up for many 

 minutes had not the experimenter lured him into the right box 

 by slightly raising the exit door. In the first series, he had to 

 be aided in five of the ten trials. The total time for the series 

 was forty-five minutes, the total number of choices, eighty-eight. 

 In the second series, he was aided in four of the trials. The 

 total time required was seventy-two minutes, and the total 

 number of choices was seventy-six. 



Throughout the first series, Sobke worked hard, but with evi- 

 dently increasing dissatisfaction. He clung persistently to his 

 acquired tendency to choose the end boxes, and after each trial 

 he returned less willingly to the starting point. 



Up to this time his attitude toward the experimenter had 

 been perfectly friendly, if not wholly trustful. But when on 

 July 21 he was brought into the apparatus for the second series, 

 he exhibited a wholly new form of behavior, for instead of at- 

 tending diligently to the open doors and devoting his energies 

 to trying to find the right box, he instead, after gazing at them 

 for a few seconds, turned toward the experimenter and jumped 

 for him savagely, throwing himself against the wire netting 

 with great force. This was repeated a number of times during 

 the first two or three trials, and it occurred less frequently later 

 in the series. Since nothing unusual had happened outside of 

 the experiment room, the suggested explanation of this sudden 

 change in attitude and behavior is that the monkey resented and 

 blamed on the experimenter the difficulty which he was having 

 in obtaining food. 



From this time on until the end of my work, Sobke was 

 always savage and both in and out of the apparatus he was 

 constantly on the watch for an opportunity to spring upon me. 

 Previously, it had been possible for me to coax him into the 

 apparatus by offering him food and to return him to his cage 

 by walking after him. But on and after the twenty-first of 



