290 



BRAINS OF RATS AND MEN 



problem, seeks to simplify it by ignoring the trouble- 

 some factors. 



The brain of the chimpanzee has relatively larger 

 projection centers than that of mane The incre- 

 ment in the human brain is almost all in the asso- 

 ciation centers and their immediate dependencies. 

 This difference in cerebral organization is reflected in 

 the behavior. The human brain can fabricate sym- 

 bols and abstractions; it can use language, numbers 

 and equations, design machines, bridges, telescopes, 

 and use them. The chimpanzee does not know the 

 meaning o{ y^ = 2px^ and he never can find out. These 

 symbolic components of behavior we know best in- 

 trospectively. We use them psychologically. We 

 know objectively the end-results of their action and 

 only a part of the intervening processes. And these 

 psychological processes are real causes of behavior. 



We have the clearest scientific evidence that bod- 

 ily changes are in causal relationship with mental 

 processes and that mental processes do cause bodily 

 activities. Certain drugs which excite or narcotize 

 ordinary protoplasm produce effects on the mind 

 quite comparable with those exerted upon the func- 

 tions of nerves and muscles, and there is no valid 

 scientific reason for refusing to draw the same infer- 

 ence regarding causal sequences in the two cases. It is 

 recognized in commercial life that certain kinds of 

 mental activity are productive work for which a daily 

 wage is paid. Even a philosopher in the employ of a 



