STUDIES OF CEEEBRAL FUNCTION IN LEAENING. VII 35 



INTEEPEETATION OF EESULTS 



The data presented in the foregoing sections seem clean- 

 cut and adequate to establish the lack of any influence of 

 injury to the occipital cortex upon the learning of brightness 

 discrimination and the quantitative relation between the ex- 

 tent of injury and the amount of practice necessary for 

 recovery from the resultant amnesia. The data tell nothing, 

 however, of the way in which these effects are brought about 

 so that their interpretation with reference to the broader 

 problems of cerebral function must be largely speculative. 

 Neither the failure of animals with occipital lesions to show 

 retardation in learning nor the quantitative effect of lesions 

 on retention conforms to expectation from current neurologi- 

 cal theory, so that we must be doubly cautious in drawing 

 conclusions. If the results stood alone in contradiction to 

 the classical views of cerebrar function, I should hesitate to 

 draw any inferences from them, but they come only as a 

 further step in a series of observations, all of which empha- 

 size the dynamic function of cerebral tissue and the lack of 

 any absolute localization of so-called mental faculties. The 

 accumulated evidence seems to demand some revision of our 

 theories of cerebral mechanism, so that, even though we can 

 form but a vague notion of the modifications which the theo- 

 ries must undergo, it seems worth while to point out some of 

 the implications of the data, both for the sake of setting 

 further problems and for the light which the more general, 

 if speculative, conclusions can throw on some of the obscure 

 questions of the cerebral mechanism of thought. 



Learning as a non-localized function 



The fact that the ability to form habits of brightness dis- 

 crimination is not in the least atfected by complete destruc- 

 tion of the occipital third of the cortex is difficult to reconcile 

 with any current theory of cortical function. The loss of 

 visual habits after destruction of this occipital region clearly 

 establishes it as a visual area in the usual meaning of the 

 term. The postoperative retention tests in no case required 



