EVIDENCES OF INSIGHT 47 



was going to use it in some way, but instead he immediately dropped it, 

 left it lying on the floor, and returned to box 3 from which he jumped two 

 or three times. 



Then, with no hesitation, he seized box 3, carried it directly to box 2 

 and placed it thereon with its open side uppermost. He now tried to 

 stand on the edge of box 3, but as this proved an unstable point from 

 which to spring, he immediately abandoned it, having made only one 

 or two futile efforts to spring from the stacked boxes. He next pulled 

 box 3 from box 2, carried it to box 1 and placed it thereon insecurely. 

 Immediately he mounted the boxes and skilfully balancing on box 3 

 as it rested on box 1, he jumped toward the banana. At the same time 

 box 3 fell to the floor, but Chim seized the banana as he sped through the 

 air and eagerly devoured his reward. 



This whole performance required less time than it takes to describe 

 it because he worked with great rapidity, jumping so hard and repeatedly 

 that at times I was afraid he might injure himself. The total time f-om 

 "setting of experiment to success was less than five minutes. 



Thus with surprising suddenness appeared the perfect 

 solution of the box stacking test. Subsequent opportunities 

 to meet the situation adequately resulted merely in the 

 perfecting of method. It is needless to describe the process. 

 Chim had gained the necessary insight for the solution of the 

 problem. That insight came not by suggestion from the 

 experimenter, as in the case of Julius, the young orang-utan, 

 but through observation, apparently supplemented by 

 reflection. 



The suddenness of Chim's success in the box stacking 

 experiment suggests the orang-utan 's solution of a multiple 

 choice problem (12). The animal, after many days of effort 

 which seemingly brought the solution no nearer, suddenly 

 achieved success. Seemingly the problem was solved over- 

 night. The only reasonable explanation of such sudden and 

 radical change in behavior is insight. Koehler has described 

 similar behavior in adolescent chimpanzees. It was, how- 



