DISTINCTIVE FEATURES OF LEARNING IN THE 

 HIGHER ANIMAL 



D. O. Hebb^ 



In the study of learning our problem is not only to understand the way 

 in which synaptic function is modified; it also fundamentally involves 

 control of the concurrent activity of the rest of the central nervous system. 

 One question is more 'molecular' and physiological, essentially concerned 

 with the relations between two individual neurones ; the other is 'molar' 

 and psychological, involving the operations of the total system. The 

 second part of my thesis is that we must develop means of dealing experi- 

 mentally with the so-called autonomous central processes whose activity 

 is at the heart of the learning process in the higher animal, and some 

 research is reported which attempts to make a contribution of this kind. 



THE PROBLEM OF EXCESS ACTIVITY IN CNS 



Learning consists of a modified direction of transmission in the CNS so 

 that, in the clearest example, a sensory excitation is now conducted to 

 effectors to which it was not conducted before. A new S-R or stimulus- 

 response connection has been established (the clearest example, but not the 

 only form of learning). The term learning may be used to refer to other 

 changes of behaviour in primitive animals, but at least in the case of the 

 mammal's acquisition of prompt, efticicnt responses, dependent on the 

 all-or-none action of neural cells conducting over considerable distances, 

 the direction of transmission must be determined at the synapse (or close 

 to it: Milner, 1959). It might therefore be thought that the problem of 

 learning is simply to discover when and how synaptic function is modified. 



The question is indeed fundamental, and must be answered before the 

 problem of learning will be solved; but it is by no means the whole 

 problem, because of complexities introduced by the structure of the CNS 

 in higher animals, and particularly in mammals and in primates. In the 

 learning process we do not have a one-to-one relation between progres- 

 sive changes of behaviour and changes at the synapse. The simplest 



^ The presentation of this paper, and some of the experimental work reported herein, was 

 made possible by the National Research Council of Canada. The experiments were done by 

 Jean Campbell, Joseph Deitcher and Eric Renncrt. 



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