128 HUMAN BIOLOGY 



i 



It has been discovered that the subject's natural basis 

 of choice in this type of memory test is the position of the 

 food container. When absolute position, or both absolute 

 and relative position are ehminated and correct response 

 depends on recognition of the object by some such visual 

 datum as color, form, size, or distance, the task is much more 

 difficult, save for man, who is able to recall and recognize the 

 food container by reason of visual or kinesthetic-verbal 

 imagery. Whether the chimpanzee or gorilla remembers 

 and recognizes the correct box through the functioning 

 of visual images or otherwise we do not know, but at least 

 it is evident that there is closer functional resemblance 

 between what may legitimately be called memory responses 

 of ape and man than between those of monkey and man or 

 monkey and other mammals. 



To the question: Do memory images or their functionally 

 equivalent biological processes appear at certain stages in 

 mental evolution and in certain classes of primates, and 

 thereafter become increasingly important as bases of adap- 

 tive response to a situation which is not continuously present 

 to the senses, we offer our opinion that the observational data 

 now available justify an affirmative reply, but they justify 

 also emphasis on the desirability of further inquiry and the 

 extreme importance of additional observations. 



Another and quite different but equally impressive exhibit 

 of memory response is provided by the behavior of primates 

 toward individuals intimately known but from whom they 

 have been separated for long intervals. We are familiar with 

 the evidences of recognition of friends by dogs, cats, and 

 other domesticated animals, but similar intimacy of acquaint- 

 ance with the behavior of monkeys and apes is limited to a 

 few individuals. Yet in these creatures the definiteness 

 and complexity of response is even greater than in the 

 other mammals, and, judging by the reports available, it 

 appears after prolonged periods of separation. There are 

 well-authenticated statements that the chimpanzee, orang- 

 outan, and gorilla may recognize species or human acquaint- 

 ances after many months of separation, and at least one 

 instance has been recorded of the recognition of a man by 

 a chimpanzee after separation of nearly four years. In 



