HABIT FORMATION IX THE ALBINO RAT 3 



discrepancy in the results of the two papers which Slonaker 

 does not attempt to explain. In the latter paper as in the 

 earlier one no attempt is made to correlate amount of activity 

 with capacity to learn. 



Yerkes' raised the question of the relation of age to habit 

 formation in the dancing mouse. He worked first on the ac- 

 quisition of the white-black discrimination habit, and later on 

 the learning of simple labyrinth pathways. The indices of 

 modifiability as given by the number of training tests required 

 to complete the habit for dancers of one and four months re- 

 spectively show that the males learned the white-black dis- 

 crimination habit more quickly at one month (30 days) than 

 at four months (120 days) while the reverse was true of the 

 females. ^ The female was superior to the male, however, in the 

 formation of the labyrinth habit. ^ In later work^" he finds 

 that male dancers ten months old learn the labyrinth more 

 rapidly than those one to two months old, while there is prac- 

 tically no difference in rapidity of learning of one to two month 

 and ten month females. The old dancers are somewhat superior 

 to the young in their ability to learn the labyrinth paths." 

 With regard to the sensory habit he says: 



"1. The dancer at one month of age acquires a particular 

 white-black visual discrimination habit more rapidly than do 

 older individuals. From the first until the seventh month there 

 is a steady and marked decrease in rapidity of habit formation; 

 from the seventh to the tenth month the direction of the change 

 is reversed. These statements hold for both sexes. 



"2. Young males acquire the habit more quickly than young 

 fahiales, but between the ages of four and ten months the fe- 

 males acquire the habit the more quickly. "'^ 



Haecker,i3 in work on the Mexican axolytl, found that the 

 habit of distinguishing between wood and meat when offered to 

 the animals in forceps, was learned with far greater difficulty 



^ Yerkes, R. M. The Dancing Mouse. The Macmillan Co., 1907. 



8 Op. cit., p. 274. 



9 Op. cit., p. 273. 



" Yerkes, R. M. Modificabihty of Behavior in its Relation to the Age and 

 Sex of the Dancing Mouse. Joiirn. Comp. Neurol, and Psychol, 19 ('09), 237-271. 



11 Op. cit., pp. 266-267. 



12 Op. cit., p. 269. 



13 Haecker. Arch. f. d. ges. Psych., 25, 1-35. 



