224 The Animal Mind 



was to test Flechsig's theory that learning depends upon the 

 presence of medullated fibres in the central nervous system; 

 this was found to be unconfirmed, since at twenty-four days, 

 when the rat is psychically mature, the medullation of its 

 fibres is highly imperfect (430). 



In his later experiments on white rats Watson's aim was 

 to investigate the nature of the sensations which guide them 

 through a labyrinth. The results will be discussed a few 

 pages farther on (431). 



Allen's work on the guinea pig was intended for comparison 

 with Watson's study of the white rat, because the young 

 guinea pig comes into the world, not helpless like the baby rat, 

 but well equipped on both the sensory and motor sides. In the 

 labyrinth, here, the mother was put at the end of the maze, 

 and the sight and smell of her were supposed to serve as the 

 stimulus to activity. Before the young animals had reached 

 the age of two days, they did not succeed in learning a com- 

 paratively simple path, but at that age they did learn it, and 

 proved the fact when the wire netting box in which they were 

 placed was turned about, by pushing at the place where the 

 opening had formerly been. At three days, they learned a 

 more complex labyrinth, and appeared to possess the learning 

 capacity of adults (4). 



In Yerkes's study of the Japanese dancing mouse, the 

 reactions to irregular and to regular labyrinths were com- 

 pared, and it was found that a maze of the latter type, that is, 

 one where left and right turns alternated, was more quickly 

 learned and more perfectly mastered than an irregular one. 

 Yerkes urges the importance of keeping account of the errors 

 made by an animal as well as the times occupied in traversing 

 a maze (469). Watson's later work on the white rat gives 

 only the turns (431). In many cases, especially with animals 

 not naturally active, the time values have little significance; 



