BASIS OF THE PKOBLEM 47 



reasons, be accepted as adequate, it does suggest the essential 

 nature of instinct, which consists in the response to a given but 

 often vague stimulus of a more or less complicated series of 

 reactions. Instinct is more than compound reflex action because 

 it involves the organism as a whole, and is accompanied by, or 

 is the outcome of, a mental process. All mental process is said 

 to involve three aspects the cognitive or the knowing of an 

 object, the affective or feeling in regard to an object, and the 

 conative or striving to or from an object and these three aspects 

 are to be found in all instinctive actions. The instinctive action 

 is initiated by a sense-impression and is followed by results so 

 important because the nervous system is innately organized to 

 respond to certain sense-impressions. It is presumed that some 

 kind of emotional excitement, however faint, always follows and 

 that it gives rise to the striving that we see in the form of move- 

 ment. Instinct has been denned as ' an inherited or innate psycho- 

 physical disposition which determines its possessor to perceive 

 and to pay attention to objects of a certain class, to experience 

 an emotional excitement of a particular quality upon perceiving 

 such an object, and to act in regard to it in a particular manner, 

 or, at least, to experience an impulse to such action '. 1 



Every one is acquainted with many examples of instinctive 

 action. ' There are many instances of insects that invariably 

 lay their eggs in the only place where the grubs, when hatched, 

 will find the food they need and can eat, or where the larvae 

 will be able to attach themselves as parasites to some host in 

 a way that is necessary to their survival. In such cases it is 

 clear that the behaviour of the parent is determined by the 

 impression made on its senses by the appropriate objects or 

 places : e.g. the smell of decaying fish leads the Carrion fly to 

 deposit its eggs upon it ; the sight or odour of some particular 

 flower leads another to lay its eggs among the ovules of the 

 flower, which serve as food to the grubs. Others go through 

 more elaborate traits of action, as when the Mason-wasp lays its 

 eggs in a mud nest, fills up the space with caterpillars, which it 

 paralyses by means of well-directed stings, and seals it up ; so 

 that the caterpillars remain as a supply of fresh animal food for 

 the young which the parent will never see and of whose needs 

 it can have no knowledge or idea.' 2 To take some examples from 



1 McDougall, Social Psychology, p. 29. a McDougall, loc. cit., p. 25. 



