Intelligence and the Acquisition of Habits. 157 



determined solely by heredity, but a new being, in which 

 that which was due to inheritance is modified by that 

 which has been acquired through individual experience. 

 Thus we may say that after a little experience the im- 

 pulsive tendencies are the net result of two factors — in- 

 heritance and individual acquisition. 



By repetition, the results of acquisition become more 

 and more firmly ingrained in the organic and impulsive 

 constitution. Habit is second nature. The congenital 

 automatism with which the animal starts gives place, 

 under the play of repetition, to an acquired automatism. 

 Between the earlier stereotyped congenital response on the 

 one hand, and the later stereotyped acquired response on 

 the other hand, lies the period of youthful plasticity. The 

 stimuli to the first — the stereotyped congenital response — 

 are to some extent unspecialized ; the chick will peck at 

 any object of a suitable size at an appropriate distance. 

 But the stimuli to the second — the acquired response — 

 are specialized, defined, or particularized. The experienced 

 chick habitually responds in one way to looper caterpillars, 

 and in a different way to cinnabars. The former, the 

 congenital responses, tend to meet the general require- 

 ments of the race ; the latter, the acquired responses, are 

 adapted to the special requirements of the individual. A 

 congenital tendency leads the little moorhen either to 

 assume the defensive attitude, or to run away, at the sight 

 of any large approaching object ; acquired tendencies 

 lead it to tolerate or welcome the approach of the familiar 

 fox-terrier or man, but to react even more vigorously on 

 the approach of the unfamiliar goose or sheep. It is in 

 the period of youthful plasticity that intelligence has its 

 most important part to play— so far as the genesis of 

 habit is concerned — at any rate, in such organisms as 

 young birds, whose intelligent adaptability is in marked 



