MENTAL LIFE OF MONKEYS AND APES 59 



July, it was impossible for me to approach him without extreme 

 risk of being bitten. 



Doctor Hamilton when told of this behavior, reported that 

 several times monkeys have shown resentment toward him when 

 they were having trouble in the experiment. I therefore feel 

 fairly confident that I have not misinterpreted Sobke's behavior. 



When on July 22 I gave Sobke an opportunity to enter the 

 apparatus, he refused, and it was impossible to lure him in with 

 food. Two hours later, having waited meantime for his break- 

 fast, he entered readily and worked steadily and persistently 

 through his third series of trials, but in no one of these trials 

 did he choose correctly. Neither on this day nor the following 

 did he exhibit resentment while at work. He apparently had 

 regained his affective poise and was able to attend as formerly 

 to the task of locating his rewards. 



During these first three series, although the ratio of right to 

 wrong choices stood to 10, there occurred a marked reduction 

 in the number of trials in which aid was necessary as well as 

 in the total number of choices, and on July 23 correct reactions 

 began to appear. Improvement during the next hundred trials 

 was steady, and fairly rapid, and on July 31, a record of seven 

 right to three wrong trials was obtained. This was surprising 

 to the experimenter, as well as gratifying, since he was eager to 

 have the animal complete this problem before work should have 

 to be discontinued. 



Everything went smoothly until August 2, when my assistant, 

 who had been left in charge of the experimental work for a week, 

 attempted to increase the number of trials per day to two series. 

 Sobke apparently was not quite ready for this increase in the 

 amount of his day's labor and refused to work at the end of the 

 first series. In this series he did less well than on the previous 

 day. The following day, August 3, unfortunately and contrary to 

 the wishes of the experimenter, the laboratory was painted and 

 there was necessarily considerable disturbance because of the 

 presence of the workmen, and in addition, the pervasive odor 

 of fresh paint. Sobke chose still less successfully on this date, 

 and on August 4, he refused to work after the eighth trial. It is 

 true that during these bad days the total number of choices 

 steadily diminished while the successes, also, diminished, or at 

 best, failed to increase. When on August 9, I returned to the 



