THE UNIQUENESS OF THE INDIVIDUAL 



irrelevant kind. In the main, though, the evidence of biology 

 serves only to identify the parameters in the equations of 

 human behaviour, if '"instincts' can be so described. 



It is not at all easy to define instinctive behaviour, but it 

 has certain properties that distinguish it clearly from be- 

 haviour of other kinds. First, instinctive behaviour is unlearried. 

 In practice, it is sometimes very difficult to decide whether a 

 particular act of behaviour is learned or unlearned, and with 

 human beings it may be well-nigh impossible. With animals it 

 is simple enough in principle. Is nest-building activity in mice 

 and birds copied or inborn? To answer this question decisively, 

 one must rear a mouse or bird in strict isolation from birth, 

 away from any possible source of information about how nests 

 are made; and one finds that a mouse so reared can make itself 

 an admirable nest. This provides one good reason for describing 

 nest-building as an instinctive act. Then again, instinctive 

 activities are '"purposeful". Never mind the teleological under- 

 tones of the idea of purpose; all I mean is that instinctive 

 activities, however complex, do in fact converge upon a certain 

 goal — mating, feeding, or whatever the case may be. The 

 functional import of instinctive activity, and the pattern of the 

 connections between its several parts, is intelligible only by 

 reference to the goal towards which it is directed. Thirdly, 

 instinctive behaviour has a Mrive"*, a sort of psychological 

 pressure behind it; a drive, for example, to find food or to find 

 a mate. The drive is temporarily discharged or assuaged by the 

 act which constitutes the goal of a particular instinctive action. 

 It is usually possible to distinguish two phases in a sequence ol* 

 instinctive behaviour: first, ''appetitive behaviour'', that earlier 

 phase in which an animal seeks the means of gratifying its 

 instincts; and second, the performance of the ''consummatory 

 act** which finally achieves the goal. The appetitive behaviour 

 that gives evidence of a hunger drive includes all the activities 

 entailed by seeking food. The consummatory act of the instinct 



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