236 Animal Intelligence 
caused the smoker to blow in his face. He was often given 
a lighted cigar or cigarette to test him for imitation. He 
formed the habit of rubbing it on his back. After doing so 
he would scratch himself with great vigor and zest. He 
came to do this always when the proper object was given 
him. |I have recounted all this to show that the monkey 
enjoyed scratching himself. Yet he apparently never 
scratched himself except in response to some sensory stimulus. 
He was apparently incapable of thinking ‘scratch’ and so 
doing.! Yet the act was quite capable of association with 
circumstances with which as a matter of hereditary organi- 
zation it had no connection. For by taking a certain well- 
defined position in front of his cage and feeding him when- 
ever he did scratch himself I got him to always scratch 
within a few seconds after I took that position.’ 
GENERAL MENTAL DEVELOPMENT OF THE 
MOoNKEYS 
It is to be hoped that the growing recognition of the worth 
of comparative and genetic studies will lead to investiga- 
tions of the mental make-up of other species of monkeys, and 
to the careful overhauling of the work done so far, including 
these rather fragmentary studies of mine. Work with three 
monkeys of one species, especially when no general body of 
phenomena, such as one has at hand in the case of domestic 
animals, can be used as a means of comparison, must neces- 
sarily be of limited application in all its details and of inse- 
cure application even in its general features. |. What I shall 
say concerning the advance in the mental development 
of the monkeys over that of other mammals may then be 
in strictness true of only my three subjects, and it may be 
left to the judgment of individuals to extend my conclusions 
