MENTAL LIFE OF MONKEYS AND APES 83 



of getting the idea of second from the right end is as clearly 

 shown by the detailed results of table 9, — the fruits of weeks 

 of experimenting. 



Certain other interesting tricks developed in Julius's behavior. 

 Thus, on July 5, there appeared the tendency to move as though 

 about to enter the right box (feint), then to stop suddenly and 

 promptly enter another box, which was, of course, a wrong one. 

 The reason for the development of this tendency could not be 

 discovered, but in connection with it, there appeared another 

 tendency which possibly can be explained. Julius took to back- 

 ing into the chosen box so that he could face the experimenter. 

 He would then, after a period of hesitation, come out and 

 promptly enter one of the other boxes. This tendency was 

 apparently due to the fact that during one or two series the 

 experimenter growled at the orang utan every time he made a 

 mistake. The growl startled him and caused him to look around. 

 He evidently felt the need of keeping his eyes on the experi- 

 menter, — hence the backing into the open box. The tendency 

 disappeared shortly after the experimenter gave up the use of 

 the growl as a method of punishing the animal for what were 

 suspected to be careless choices. 



Curiously enough, it was not until July 10 that direct choice 

 of the right box was made at all frequently. Previously, selec- 

 tion of it had been made almost invariably after approach to 

 other boxes. But in the second series for July 10 there was an 

 extraordinary improvement in method. This developed in the 

 presence of two visitors, and it is therefore all the more sur- 

 prising. The choices were made not only directly, but with 

 decision and evident certainty that was quite at variance with 

 the previous behavior of the animal. 



All the while through variation of methods, I was seeking to 

 discover the best means of holding the orang utan to his maxi- 

 mum effort and care in attempting to select the right box. One 

 day it would seem as though forcing him to make round trips 

 with rewards only for correct first choices proved most satis- 

 factory, and the next it might seem equally clear that punish- 

 ment by confinement for thirty seconds or sixty seconds, with 

 reward for correct choice in every trial, yielded better results. 

 •In the end I had to admit that no best method had been demon- 

 strated and that I had failed to develop conditions which served 



