170 BEGINNINGS OF INTELLIGENCE 



the states of consciousness which it endeavors to expel are 

 the correlatives of beneficial actions, it must quickly disap- 

 pear through persistence in, the injurious and avoidance 

 of the beneficial. In other words, those races of beings only 

 can have survived in which, on the average, agreeable or 

 desired feelings went along with activities conducive to the 

 maintenance of life, while disagreeable and habitually- 

 avoided feelings went along with activities directly or in- 

 directly destructive of life; and there must ever have been, 

 other things equal, the most useful and long-continued 

 survivals among races in which these adjustments of feelings 

 to actions were the best, tending ever to bring about perfect 

 adjustment." 



This explanation which has become widely accepted 

 leaves a fundamental question unanswered. It does not 

 explain why certain acts are stamped in and certain others 

 stamped out. Of the mechanism of this process, which is 

 the real problem involved in the pleasure-pain reaction, 

 we are as ignorant as before. The explanation means that 

 animals which took pleasure in following acts that brought 

 them benefit were preserved and those that did not behave in 

 this manner were eliminated. But why does an animal tend 

 to repeat an act that brings it pleasure and avoid one that 

 produces pain? It seems so natural for creatures to behave 

 in this way that the existence of any problem here is usually 

 unsuspected, but this is the problem that confronts us when 

 we endeavor to obtain a clear understanding of the way 

 in which intelligence develops out of instinct. 



In the pleasure-pain response we have two problems of a 

 quite different nature: (1) the problem of how behavior is 

 modified by its results, and (2) the problem of why pleasure 

 is associated with certain physiological activities, such as 

 securing movements, and pain with others, such as avoiding 



