310 The Animal Mind 



daily interested in testing Flechsig's theory that learning 

 depends upon the presence of medullated fibres in the cen- 

 tral nervous system. The theory was unconfirmed, for 

 such medullation is highly imperfect in the rat at twenty- 

 four days of age, yet at this age Watson's rats learned a 

 labyrinth more quickly than did the adults. The rat 

 belongs to the class of animals that are born unable to 

 care for themselves, and before those observed by Watson 

 had reached the age of twelve days, they were unable to 

 find their way by a simple maze path back to the mother. 

 The superiority of young rats over adults in learning a 

 maze path is apparently due to their greater activity; 

 they make more useless movements, and in solving a puzzle 

 box they are at a disadvantage as compared with their 

 elders. 



Allen's (4) work on the guinea pig was intended for com- 

 parison with Watson's study, because the 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 tests 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 reached 

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

 comparatively 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 been. At three days they 

 learned a more complex maze, and appeared to possess the 

 learning capacity of adults. 



Yerkes (821) found that the dancing mouse at one month 

 old learns a black-white discrimination faster than an older 

 mouse. From one to seven months of age there is a de- 

 crease in learning speed ; from seven to ten months, an 



