CHAPTER VIII 



PLEASURE, PAIN, AND THE BEGINNINGS OF 

 INTELLIGENCE 1 



"Apprehensio sensitiva non attingit ad communem rationem 

 boni, sed ad aliquod bonum particulare, quod est delectabile. Et 

 ideo secundum appetitum sensitivum, qui est in animalibus, opera- 

 tiones quaeruntur propter delectionem." THOMAS AQUINAS, Summa 

 Theologica. 



Psychologists nowadays with comparatively few exceptions 

 agree hi regarding intelligence not as a faculty standing in 

 sharp contrast to instinct, as was formerly taught, but as one 

 resting on a foundation of instinct, and gradually growing 

 out of behavior of the purely instinctive type. The term 

 intelligence is used here in the wider sense as embracing all 

 those forms of profiting by experience through the formation 

 of associations. It therefore includes psychic activity rang- 

 ing from simple associative memory to complex trams of 

 reasoning. What distinguishes intelligence from instinct is 

 that in the latter the connections between acts are based 

 upon hereditary organization, whereas ha the former they 

 are established through experience. The apparently new 

 thing involved in intelligent behavior is the power of form- 

 ing associations. So far as we can judge of the psychic states 

 of an animal from its behavior, animal intelligence in its first 

 manifestations consists in repeating acts which bring pleasure 

 and in avoiding things which cause pain, and a discussion of 

 the transition from instinct to intelligence naturally involves 



1 This chapter is taken with some modifications from an article of the 

 same title contributed by the writer to the Journal of Comparative Neu- 

 rology and Psychology. I am indebted to the editor for permission to 

 reprint a considerable part of the article here. 



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