GENERAL PRINCIPLES 51 



remain unmodified throughout life. The chick, however, or the 

 imago insect, is something more than this. It affords evidence 

 of the accommodation of behaviour to varying circumstances. It 

 so acts as to lead us to infer that there are centres of intelligent 

 control through the action of which the automatic behaviour can 

 be modified in accordance with the results of experience. When, 

 for example, a young chick walks towards and pecks at a lady-bird, 

 the like of which he has never before seen, the behaviour may be 

 purely instinctive; and so, too, when he similarly seizes a wasp- 

 larva. . . . But when, after a few trials, the chick leaves lady-birds 

 unmolested while he seizes wasp-larvae with increased energy, he 

 affords evidence of selection based on individual experience. And 

 such selection implies intelligence in almost its simplest expression. 

 We may say, therefore, that, whereas instinctive behaviour is 

 prior to individual experience, intelligent behaviour is the outcome 

 and product of such experience. This distinction is presumably 

 clear enough; and it is one that is based on the facts of obser- 

 vation. But we must not fail to notice that, though the logical 

 distinction is quite clear, the acquired modifications of behaviour, 

 which we speak of as intelligence, presuppose congenital [i.e. in- 

 herited] modes of response which are guided to finer issues. We 

 may say then, that where these congenital modes of response take 

 the form of instinctive behaviour, there is supplied a general plan 

 of action which intelligence particularizes in such a manner as 

 to produce accommodation to the conditions of existence." The 

 quotation just given implies, what is no doubt true, that in the 

 course of mental evolution Instinct does not become Intelligence, 

 but is gradually replaced by it, i.e. inherited specialized behaviour 

 is replaced more or less by self-specialized behaviour. The larger 

 the amount of such replacement the greater the intelligence. And 

 this enables us to understand the peculiar helplessness of the 

 young of higher Mammals, especially those of our own species. 

 The complex instincts of lower forms have been lost, and it takes 

 a long time to learn how to act intelligently. The remark does 

 not apply to all helpless young, for in some of these, e.g. in nest- 

 ling birds, such instincts are only deferred. The influence of 

 strongly-developed parental affection is noticeable in both cases. 



To interpret the action of animals with any likelihood of 

 accuracy it is necessary to avoid two extreme views of opposite 

 kind. One of these ascribes almost human attributes to even the 



