CHAPTER X 



THE MODIFICATION OF CONSCIOUS PROCESSES BY 

 INDIVIDUAL EXPERIENCE 



(THE reactions of animals to stimulation show, as we re- 

 view the various animal forms from the lowest to the highest, 

 increasing adaptation to the qualitative differences and to the 

 spatial characteristics of the stimuli acting upon them. It is 

 therefore possible to suppose that the animal mind shows 

 increasing variety in its sensation contents, and increasing 

 complexity in its spatial perceptions. But besides this 

 advance in the methods of responding to present stimu- 

 lation, the higher animals show in a growing degree the 

 influence of past stimulation. While a low animal may 

 apparently react to each stimulus as if no other had affected 

 it in the past, one somewhat higher may have its reaction 

 modified by the stimulation which it has just received. An 

 animal still more highly developed may give evidence of being 

 affected by stimuli whose action occurred some time before ; 

 and finally, in certain of the vertebrates, perhaps, as in man, 

 conduct may be determined by the presence in consciousness 

 of a memory idea representing a past stimulus. " Learning 

 by experience," or "associative memory," as we saw in Chap- 

 ter II, has been regarded as the evidence par excellence of the 

 existence of mind in an animal. That it does not serve this 

 purpose to entire satisfaction was also pointed out in that 

 earlier chapter, and will be more clearly apparent as we survey 

 in the following pages the various ways in which an organ- 



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