132 Studies in Animal Behavior 



with a selective agency which preserves and intensi- 

 fies certain kinds of behavior and rejects others on 

 the basis of their results a kind of "sorting demon" 

 in the realm of behavior. What could be more tele- 

 ological ! 



The fact that what is pleasant is usually beneficial 

 and what is painful is usually injurious may be ex- 

 plained with some plausibility as the result of nat- 

 ural selection, as was first contended by Herbert 

 Spencer. Animals which took pleasure in doing 

 things which were bad for them and which experi- 

 enced pain in doing things which were good for them 

 would be very apt to fare ill in the struggle for 

 existence. Natural selection would ever tend to 

 bring about a condition in which the pleasant means 

 the organically good and the painful means the re- 

 verse. We should not expect the correspondence, 

 if brought about in this way, to be complete, and it 

 is rather in favor of the theory that we do not find 

 it so. 



But granting this contention of Spencer, there is 

 the important question still left unanswered, namely, 

 Why do animals follow what is pleasant and avoid 

 what is painful? In other words, why does pleas- 

 ure reinforce and why does pain inhibit? Here is 

 another fundamental problem and we find that Spen- 

 cer with his usual appreciation of fundamental prob- 

 lems was on the ground early with a theory. Pleas- 

 ure, according to Spencer, is the concomitant of a 

 heightened nervous discharge; pain the concomitant 



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