ANIMAL BEHAVIOUR 203 



experience. Such behaviour is, I conceive, a more or less 

 complex organic or biological response to a more or less 

 complex group of stimuli of external and internal origin, 

 and it is, as such, v^holly dependent on how the organism, 

 and especially the nervous system and brain centres, have 

 been built through heredity under that mode of racial prep- 

 aration which we call biological evolution " (Instinct and 

 Experience, 1912, p. 5). 



It is confusing to use the term instinctive so loosely that 

 it becomes almost equivalent to hereditary or inborn, as in 

 phrases like instinctive pugnacity or instinctive gregarious- 

 ness, for the usefulness of the term is in reference to specific 

 behaviour. Yet it may be legitimate and useful to distin- 

 guish between general instinctive tendencies and specialised 

 instinctive behaviour. A general instinctive tendency is the 

 expression of an inborn impulsion which has not much par- 

 ticular content, such as is shown by mammals who are about 

 to become mothers for the first time, or by an isolated hen- 

 bird who fumbles at nest-making, or in the so-called ' sex- 

 instinct '. Thus we ourselves have many instinctive ten- 

 dencies, but few instincts. These general instinctive ten- 

 dencies are to be distinguished from fundamental appetites 

 such as hunger, and also from general tropisms, illustrated, 

 for instance, when young birds gather under a tea-cosy as 

 under a mother — where we have evidently to do with sim- 

 ilar responses to similar stimuli. 



§ 9. Theories of Instinct. 



It is too soon to come to any hard-and-fast conclusion 

 in regard to the nature of instinctive behaviour. We have 

 not yet got the facts fully before us, and there is much 

 need of more experimental study. It is almost certain that 



