140 Instinct and Intelligence 



ised layers of nerve cells and fibres possessing 

 intellectual properties. The nervous substance 

 and functions of the instinctive or basal elements 

 of the brain are. strictly hereditary, having a 

 pedigree extending over long geological periods 

 and therefore difficult to alter and almost im- 

 possible to obliterate. 1 On the other hand, the 

 association or neopallial elements of the brain 

 are, philogenetically, of recent origin; their 

 hereditary qualities are not so firmly ingrafted 

 in its substance as those inherent in the instinc- 

 tive centres; psychical nervous substance is 



1 Mr. W. McDougall is of opinion that modifications of instinc- 

 tive action may be effected, first, by an animal learning to dis- 

 criminate by experience gained from success or failure of its 

 instinctive behaviour. Secondly, an animal may learn to react 

 with one of its instinctive modes of behaviour to an object of a 

 kind towards which it at first remained indifferent. The third 

 type of modification of instinctive behaviour consists of a modifica- 

 tion of the bodily activities that are directed upon the object of 

 the instinct. He remarks that "when the behaviour of an animal 

 exhibits modification of a purely instinctive mode of behaviour of 

 any one of these kinds, we say that it has profited by experi- 

 ence and behaves intelligently. All animal behaviour is, then, 

 either purely instinctive or intelligent ; and when we say intelligent, 

 we mean that it is such as implies some degree of modification 

 of the innate structure of the mind through experience of success 

 or failure, pleasure or pain, in the course of purposive activity. 

 Intelligent behaviour thus always involves modification of instinc- 

 tive modes of behaviour, and intelligence presupposes instinct, for 

 unless a creature possessed instinct of some kind, all basis for the 

 play of intelligence would be lacking, there would be no tendencies 

 to be modified, and modification of pre-existing tendencies is the 

 essence of intelligent activity." (Psychology, "The Study of Be- 

 haviour," pp. 163, 164.) 



