CEREBRAL FUNCTION IN LEARNING 101 



operated animals and normals is much less than between paretic 

 and non-paretic and it is therefore very unlikely that it could \ 

 have resulted in an acceleration of learning of more than 39 per 

 cent, which is the difference found between non-paretic operated 

 and normal animals. It can not, therefore, have altered a sig- 7 

 nificantly reduced ability to learn into an apparent heightened 1 

 ability. At most, it can only have obscured an actual equality ._i 

 The evidence from the time consumed in training also fails to 

 reveal a marked inferiority of the operated animals and there 

 is a seeming equality in learning ability between animals with 

 great and with small lesions. 



All the data then seem to point toward an equality of normal 

 and partially decerebrate animals with respect to learning ability. 

 Certainly there is no evidence to show that the injuries to the 

 cerebrum resulted in any reduction of the power to learn. 



The bearing of the experiments on cerebral function in learning 



The interest of the experiments lies, after all, not so much in 

 the comparative rates of learning of normal and partially decere- 

 brate animals as in the fact that the animals can learn at all 

 rapidly after such extensive brain injuries. And on this point the 

 experiments are absolutely conclusive. They have covered every 

 portion of the cerebrum in one or another animal, and with bi- 

 lateral operation every region except a small area at the base of j 

 the temporal lobes (figure 9). No single part of the cerebrum 7 

 has proved to be necessary for the learning of the double-plat- J 

 form box and no single part has proved to be significantly more 

 efficient in learning than any other part. For the acquirement 

 of the habit the various parts of the cerebrum seem to be abso- 

 lutely equipotential. Moreover, at least 50 per cent of the cor- 1/ 

 tex can be dispensed with without marked deterioration and there 

 seems to be no relation between the absolute quantity of cerebral 

 cortex functional and the ability to learn. 



Whether greater injury than 50 per cent would cause deteri- 

 oration has not been determined. I have made some attempts to 

 produce greater lesions but have not yet developed a satisfactory 



