The Beginnings of Intelligence 135 



no attempt to explain why pleasure is associated 

 with certain experiences and pain with others. Such 

 association may turn out to be as inexplicable as 

 the problem why stimulation of the optic nerve gives 

 rise to a sensation of light instead of some other 

 kind of feeling. What it is feasible to attempt to 

 explain is why certain responses tend to be repeated 

 and others tend to be inhibited. And this can be 

 explained with some plausibility as due to the con- 

 gruity or incongruity of the reactions which come 

 to be associated. For the sake of illustration let 

 us consider again the chick which pecks at a nasty 

 caterpillar. The irritation set up by the caterpillar 

 in the chick's mouth evokes movements of with- 

 drawal and ejection. The two responses of peck- 

 ing and ejection become associated, but as the two 

 movements are contradictory the result is inhibition. 

 The pecking reaction no longer occurs in the pres- 

 ence of a second nasty caterpillar, not because of 

 any stamping-out influence of the physiological con- 

 comitant of pain, but because it becomes joined with 

 an antagonistic reaction. 



In a previous paper by the writer the attempt 

 was made to extend the theory of Hobhouse to 

 account for the reinforcement commonly held to be 

 caused by pleasure. The assumption was made 

 that this process is due to an organic congruity of 

 the reactions. If the caterpillar pecked at is a 

 savory one there is set up the reflex of swallowing. 

 Pecking and swallowing form the normal elements 



