190 SOCIAL BEHAVIOUR 
not imitate any actions, but behaviour of certain specific types, 
the imitation of which has been engrained through the action 
of natural selection. 
What generalization, then, can be drawn from this some- 
what indefinite group of facts, to which many others of like 
import could be added from observations on the young of 
mammals? What is their relation to instinctive procedure in 
general? It would seem that they are characterized by a 
special relation of the external stimulus to the response. 
When this stimulus is afforded by the behaviour of another 
animal, and the responsive behaviour it initiates is similar to 
that which affords the stimulus, such behaviour may be termed 
imitative. A chick sounds the danger note; this is the 
stimulus under which another chick sounds a similar note, 
and we say that the one imitates the other. Such an action 
may be described as imitative in its effects, but not imitative 
in its purpose. Only from the observer’s standpoint does such 
instinctive behaviour differ from other modes of congenital 
procedure. It may be termed biological, but not psychological, 
imitation. And if it be held that the essence of imitation lies 
in the purpose so to imitate, we must find some other term 
under which to describe the facts. This does not seem neces- 
sary, however, if we are careful to qualify the term “ imita- 
tion” by the adjective “instinctive” or “biological.” And 
the retention of the term serves to indicate that this is the 
stock on which deliberate imitation is eventually grafted. 
The fact that instinctive imitation leads, under natural 
conditions, to behaviour which is already familiar to us 
in the species concerned, prevents us from recognizing the 
influence of this social factor so easily as might otherwise be 
the case. The abnormal arrests our attention more readily 
than the normal, and hence the cases commonly cited are 
generally those which strike us as unusual, such as the 
imitation of human sounds by the parrot. But if the 
young inherit a tendency to imitate certain actions of their 
parents, and if there is among the members of a gregarious 
species such instinctive imitation as shall tend to keep them 
