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 stimulation, 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 deter- 

 mined by the presence in consciousness of a memory idea 

 representing a past stimulus. "Learning by experience," 

 or "associative memory/' as we saw in Chapter 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 



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