THE PROBLEM OF LEARNING I9I 



sary In such reactions. In each of these different 

 groups, first one region of the "old brain," then 

 another comes to dominate and regulate the activi- 

 ties of the animal. The cerebellum performs this 

 role in certain fishes, while the mid-brain is in con- 

 trol in frogs. It is only among the higher animals 

 and man that the great regulating center for all 

 of the higher mental processes is located in the 

 cerebrum. The halves of the cerebrum are con- 

 nected by a prominent bridge (corpus callosum) 

 that brings all of the regions in this complex 

 organ into intimate connection. In eminent men 

 so far studied this bridge is much thicker than in 

 the brains of savages or Ignorant workmen, 

 clearly indicating that such an extensive associa- 

 tion between the parts of the "new brain" Is 

 significant. 



The learning experiments In animals through 

 the use of common stimuli aimed to have each of 

 the animals exhibit a specific series of reactions. 

 It was hoped to establish new habits which would 

 be retained and in each case the experimenter was 

 successful. When one tries now to formulate an 

 hypothesis of just how this was done, he enters a 

 field of Intense controversy. 



Nature has always been a stern teacher for the 

 animals that have even survived. Habits and In- 

 stincts have become deeply Ingrained Into their 

 very being. Those with a complex brain and a 



