MENTAL LIFE OF MONKEYS AND APES 43 



2. Sobke, Pithecus rhesus 

 Problem 1. First at the Left End 



Sobke was somewhat afraid of the experimenter when the 

 investigation was undertaken, and instead of willingly coming 

 out of his cage when the door was raised, he often had to be 

 coaxed out and lured into the apparatus with food. Whereas 

 Skirrl was frank and rather aggressive, Sobke was stealthy in 

 his movements, furtive, and evidently suspicious of the experi- 

 menter as well as of the apparatus. He was perfectly safe to 

 approach, but would not permit am^one to touch him. After 

 a few days, he began to take food from the hands of the experi- 

 menter. 



Preliminary work to acquaint this monkey with the routine 

 of the experiment was begun on April 13. As in the case of 

 Skirrl, he was lured into the apparatus and was taught the 

 route through the boxes to the starting point by being allowed 

 to obtain food once each day in each of the nine boxes. The 

 procedure was simple. The entrance door and the exit door 

 of a particular box were raised and the animal admitted to the 

 reaction-compartment and permitted to pass through the box 

 whose doors stood open, take its food, and return to the starting 

 point. Sobke verv' quickh^ learned the route perfectly and 

 came to work steadily and rapidly. After five days of prelim- 

 inary work of this sort, he was so thoroughly accustomed to 

 the apparatus that it was evidently desirable to begin with regu- 

 lar training experiments. 



The first series of trials was given on April 19. Both punish- 

 ment and reward were employed from the first. The punish- 

 ment consisted of confinement for thirty seconds in each wrong 

 box, and the reward of a small piece of banana, usually not 

 more than a tenth of a medium sized banana for each correct 

 choice. The total time for the first series of trials was fourteen 

 minutes. This indicates that Sobke worked rapidly. My 

 notes record that he worked quickly though shyly, wasted almost 

 no time, made few errors of choice, and waited quietly during 

 confinement in the boxes. In this, also, he differed radically 

 from Skirrl who was restless and alwa^^s tried to escape from 

 confinement. 



Throughout the work on problem 1, punishment and reward 



