MENTAL LIFE OF MONKEYS AND APES 69 



Problem 2. Second j'rom the Right End 



Julius was given four days' rest before being presented with 

 problem 2. He was occasionally fed in the apparatus, but regular 

 continuation of training was not necessary to keep him in good 

 form. During this rest interval, locks were attached to the doors 

 of the apparatus so that the experimenter by moving a lever 

 directly in front of him could fasten either one or both of the 

 doors of a given box by a single movement. On May 13 Julius 

 was given opportunity to obtain food from each of the boxes 

 in turn, and trial of the locks was made in order to familiarize 

 him with the new situation. He very quickly discovered that 

 the doors could not be raised when closed, and after two days 

 of preliminary work, he practically abandoned his formerly per- 

 sistent efforts to open them. The locks worked satisfactorily 

 from a mechanical point of view as well as from that of the adapta- 

 tion of the animal to the modified situation. 



Problem 2 was regularly presented for the first time on May 

 17, on which day a single series was given. The period of pun- 

 ishment adopted was twenty seconds, and for each successful 

 choice a small piece of banana was given as a reward. After 

 the first trial in this series, in which Julius repeatedly entered 

 the first box at the left, that is box 7, there was but slight ten- 

 dency to reenter the first box at the left of the group. Instead, 

 Julius developed the method of moving box by box toward the 

 right end of the group. The choices were made promptly, and 

 their systematic character enabled the animal to obtain his 

 reward fairly quickly, in spite of the large number of mistakes. 



In the second series, the orang utan developed the interesting 

 trick of quickly dodging out of the wrong box before the experi- 

 menter could lower the door behind him. This he did only 

 after having been punished for many wrong choices to the point 

 of discouragement. The trick was easily broken up by the 

 sudden lowering of the entrance door as soon as he had passed 

 under it. 



There appeared on May 21 an unfavorable physical condition 

 which manifested itself, first of all through the eyes which ap- 

 peared dull and bloodshot. On the following day they were 

 inflamed and the lids nearly closed. Julius refused to eat, and 

 experimentation was impossible. Until June 2 careful treat- 

 ment and regulation of diet was necessary. He passed through 



