Considerations on the Problem of Learning 141 



rones rather than of the animal as a whole, and to 

 temporary rather than permanent maintenance and 

 hindrance." 



Now the modification of behavior through 

 changes in the neurones is concerned chiefly with 

 what affects the permeability of certain lines of 

 communication in the nervous system. The seat 

 of these changes in permeability is thought by many 

 physiologists to reside in the synapses or membranes 

 between the ends of anastomosing processes of the 

 nerve cells. While the experimental evidence for 

 this conclusion is rather meager we may adopt it 

 provisionally as perhaps the most plausible view 

 at the present time. The condition which permits 

 the ready transfer of impulses from one neurone to 

 another Thorndike calls the "intimacy of the syn- 

 apse," and he formulates the following provisional 

 hypothesis to account for the process of learning: 

 "A neurone modifies the intimacy of its synapses 

 so as to keep intimate those by whose intimacy its 

 other life processes are favored and to weaken the 

 intimacy of those whereby its other life processes 

 are hindered. The animal's action-system as a whole 

 consequently does nothing to avoid that response 

 whereby the life processes of the neurones other 

 than connection changing are maintained, but does 

 cease those responses whereby such life processes of 

 the neurones are hindered. 



"This hypothesis has two important consequences. 

 ^ First: Learning by the law of effect is then more 



