596 LIFE : OUTLINES OF GENERAL BIOLOGY 



zees, one of which was in vigorous health. As an expert psychologist 

 he was peculiarly careful not to rely on single observations. Com- 

 pared with the critical scrupulousness of Kohler and Yerkes, most 

 of the old work — though not that of Romanes — appears relatively 

 .'uiecdotal. 



From Yerkes's results it is plain that there are very marked 

 individual differences, and that bodily health counts for much. 

 The male, Chim, who was in vigorous health, showed himself 

 sanguine, venturesome, trustful, friendly, and energetic. The 

 female, Panzee, who was in poor health, showed herself distrustful, 

 retiring, and lethargic. Chim's behaviour suggested in most cases 

 unusual intelligence; Panzee's, on the other hand, suggested stu- 

 pidity. This points to the importance of the health factor. Sometimes 

 the difference in behaviour might have to do with sex. Thus the 

 male habitually strove to evade the disciplinarian, while the female 

 tried to get into his arms. One day Chim carefully plucked some 

 blossoms and presented them to a lady attendant. He would dance 

 in a lively way, keeping time to music; but Panzee, though interested 

 in music, never danced. Chim constructed nests, but though Panzee 

 once or twice climbed the tree to take a look at one, she was not 

 much interested, nor did she herself show any building bent. 



There was abundant evidence of high sensory equipment, visual 

 in particular. But again it was the vigorous Chim who was most 

 interested — even in the distant mountains! He also was much 

 quicker to appreciate something of the significance of a new situa- 

 tion. Thus it was striking to see Chim dealing with a juicy orange 

 halved across the equator, for after a little experimentation he 

 learned to extract the pulp without losing a drop of the juice. 

 Panzee's technique in eating a half-orange was crude and careless 

 in comparison, and commonly resulted in the loss of more or less 

 of the juice. 



Of intelligent appreciation of a problem perhaps the best example 

 was in connection with lifting one box on to another in order to 

 secure a banana which was otherwise out of reach. The solution 

 came within five minutes. Dr. Yerkes has no doubt that Chim 

 worked with ideas and made inferences. "Most surprising and 

 impressive in Chim's behaviour", he writes, "was the continuity of 

 attention, high degree of concentration on his task, evident purpose- 

 fulness of many, if not most, of his acts, his systematic survey of 

 problematic situations, his rapid elimination of unsuccessful acts or 

 methods, and his occasional pauses for reflection." 



In this connection we may here recall Darwin's story of the 

 monkey-trainer who used to buy his animals from the dealer for £i 

 each, but offered up to £5 each if he might have leave to choose, 

 one by one, out of batches to be lent him for a period of trial. When 

 Darwin asked him the reason for this, he explained that the only 



