MENTAL EVOLUTION IN THE PRIMATES 1 29 



these instances, to judge from our own experience, the 

 behavior frequently is so distinctive, appropriate, and 

 indicative of identification of the particular individual that 

 one is not tempted to question the existence of memory 

 processes. Whether or not they be experiences of the human 

 order we shall not presume to say, although it is entirely 

 clear that if they are not comparable with our own mental 

 content they are at least aspects of psychobiological processes 

 which serve the same purpose as does reproductive imagina- 

 tion in man. 



Creative or constructive as contrasted with reproductive 

 imagination has seldom been sought for by the experimental 

 student of animal behavior, but by various authors it has 

 been suggested that the use of environmental objects as 

 tools or instruments may imply the presence of constructive 

 imagination. Such activity is virtually lacking in other 

 mammals than the primates: it appears in steadily increasing 

 variety and frequency from lemur to man. Narrowly limited 

 in the monkeys, to judge by existing information, it is far 

 more conspicuous and serviceable in the apes, although 

 even in them markedly less well developed than in man. 



The use of objects as aids in adaptation marks the begin- 

 ning of behavioral adaptation through modification of 

 environment as contrasted with the process of self-adapta- 

 tion. It is observable that whereas most existing animals, 

 more or less rapidly and in various ways, as also in varying 

 degrees, adapt to their environment, man is distinguished 

 by the extent of his ability to shape environment to his 

 needs and desires. Thus he extends the possibilities of 

 adaptation and enormously increases the potentialities of 

 his life. It is by virtue of his constructive imagination and 

 his manual dexterity that he is able increasingly to 

 control his world. 



For our present interest in adaptation the important 

 question is: Are there evidences in ape, monkey, or other 

 primate of the use of objects as tools or of their modification 

 to serve as such? 



Already the fact of occasional use of sticks and other 

 simple objects as implements has been recorded by us for 

 both monkeys and apes. The latter, however, greatly excel 



