CEREBRAL FUNCTION IN LEARNING 97 



criterion of error effectively eliminates the personal equation of the 

 experimenter. Are we then to conclude that the removal of a 

 portion of the cerebrum does improve ability to learn? Such a 

 conclusion seems preposterous, but there is no evidence at present 

 from which I can deduce the flaw in the experiments. It is most ; 

 probable that the difference between the groups is merely a 

 chance result which would not hold if a larger number of cases j 

 were studied. 



From the test it seems clear, at least, that the operated 

 animals are able to learn as readily as do normal ones. The 

 experiments have failed to reveal any retardation of the learning 

 process resulting from the removal of the anterior third of the 

 cerebrum. 



The effects of destruction of deep-lying structures 



The more important cerebral structures which lie below the 

 surface and which might play some part in learning are the cor- 

 pora striata, the hippocampal lobes, and the corpus callosum. 

 Many of the animals trained on the double-platform box show 

 extensive destruction of these structures and make it possible 

 to test their function in learning. 



The animals showing injuries to the hippocampal lobes were: 



Number 5. Left hippocampal lobe injured. 



Number 6. Left hippocampal lobe extensively injured. 



Number 7. Right hippocampal lobe replaced by a cyst. 



Number 8. Both hippocampal lobes slightly injured. 



The average number of trials required for learning by these 

 four animals was 81.2, which is practically the same as the aver- 

 age for all operated animals. The hippocampal lobes are not 

 more important for learning than other parts of the cortex. 



The animals showing injury to the corpora striata are : 



Number 3. Complete destruction of the left C. S. 



Number 4. Extensive injury to the right C. S. with probable 

 interruption of its connections with the thalamus. 



Number 5. Probable section of the connection of the left C. S. 

 with the thalamus. 



PSTCHOBIOLOGT, VOL. H, NO. 1 



