112 ROBERT M. YERKES 



stealthy and indirect manner, and second, his failure to use 

 other means of obtaining the bait than that supplied by the 

 observer. Instead of looking straight at the experimenter, or 

 at the object which he wished to obtain, he apparently looked 

 and attended elsewhere. For this reason it was often difficult 

 to decide whether or not he had noticed the bait or the boxes. 

 Finally I was led to conclude that he usually knew exactly what 

 was going on and had in his furtive way noted ail of the essential 

 features of the situation, and that his manner was extremely 

 indicative of his mental attitude of limited trust. Both Julius 

 and Skirrl went to the opposite extreme in the matter of direct- 

 ness, or as we should say in human relations, frankness. They 

 would look the experimenter directly in the eye, and they usu- 

 ally gazed intently at anything, such for example as the bait, 

 that interested them. Sobke, even when very hungry, instead 

 of going directly toward the bait, and trying to obtain it, usually 

 did various other things as though pretending that he had no 

 interest in food. 



On the following day, June 15, the three boxes were again 

 placed nearly under the banana, but this time the two smaller 

 boxes, numbers 1 and 2, were pushed to the extreme end of 

 the lower box and so far from the bait that it could not be 

 reached from box 1. It was necessary then for the animal to 

 push boxes 1 and 2 along on box 3 until they were nearer the bait. 



Sobke, when admitted to the cage, evidently noticed the 

 banana, but as formerly, he made no immediate effort to obtain 

 it. After w^andering in search of food and quarreling with the 

 other monkeys for several minutes, he went to the boxes, pushed 

 the topmost one, number 1, off on to the floor, and then carried 

 it into his cage where he quickly tore one side off. He next 

 returned to the large cage, climbed up on box 2, and he was 

 able, by jumping, to reach and obtain the banana. 



As Sobke was very good at jumping, his new method ren- 

 dered the box stacking experiment of uncertain value, since it 

 was next to impossible so to arrange the spatial relations of bait 

 and boxes that he should be neither discouraged by too great 

 a distance nor encouraged to jump by too small a distance. 

 Evidently it would be more satisfactory to simplify the con- 

 ditions by trying to discover, first of all, whether he would use 

 a single box as a means of reaching the reward. 



