The Memory Idea 283 



the actual chase or warfare. The kitten watches the string, 

 for which she has no practical use, as intently as she watches 

 the bird for which she does have a practical use; the dogs 

 rolling over and over each other are nearly as absorbed in each 

 other's movements as if they were in deadly combat. 



That relief from practical necessity which will serve the 

 purpose we are considering is to be found not in play, but 

 in infancy. If a creature spends the period during which 

 its nervous system is undergoing most rapid development 

 in a state of complete shelter and protection from external 

 danger, with all its vital needs supplied, then the nervous 

 energy which under other conditions would be expended in 

 the processes underlying attention to external stimuli is 

 free to be so devoted that attention will be directed toward 

 the creature's inner experiences. The human baby, while 

 he may be interested in lights and sounds, in external impres- 

 sions, does not need to be alert and watchful lest he miss his 

 dinner or be dined on himself; his attention is free to be 

 expended on his own movement experiences as well as on 

 anything else. That young children do go through a stage 

 of intense interest in the sensations resulting from their own 

 movements is a fact made clear from many observations. 

 The curious period of "self-imitation" in the child when it 

 repeats for an indefinite period the same movement or sound,, 

 over and over again (8), is very likely a period of vivid 

 attention to movement sensations ; and just as the movement 

 will take place if we attend exclusively to the idea of it, so 

 here the child's developed attention to the sensations result- 

 ing from the movement reinstates the movement itself. 



That the prolonged period of human infancy is of advan- 

 tage to the intellectual life of man because it means plasticity, 

 the absence of fixed instincts that would take the place of 

 acquisition by individual experience, was first pointed out by 



