HABIT FORMATION IN THE ALBINO RAT 43 



The number of trials required by the rats in order to learn 

 the maze increases with age except in the case of the three 

 hundred day group where the average is very slightly below 

 that of the two hundred day group. 



The sixty-five day males learned the problem in fewer trials 

 than the twenty-five day ones but the females of the older group 

 required more trials than those of the younger. There is rather 

 a sharp dividing line between the young animals (25 and 65 

 days) and the old animals (200 and 300-days) the former ac- 

 quiring the maze habit with considerably fewer trials than the 

 latter. 



The total time consumed in perfecting the habit also shows 

 a regular increase with age except for the sixty-five day rats 

 whose time record is slightly below that of the twenty-five day 

 ones. The apparent superiority of the older group over the 

 younger is attributable solely to the record made by the males, 

 since the females at sixty-five days have a higher record than 

 those at twenty-five days. Again we see that the two younger 

 groups are quite distinct from the two older ones, requiring 

 considerably less total time in which to learn the problem. 

 The high average of the three hundred day group is due in part 

 to the large number of failures which occurred in early trials 

 at that age, but is also partly attributable to their slower bodily 

 movements. 



Total distance shows a regular increase with increasing age 

 except for the sixty-five day group, where again the lowering 

 of the average is due to the superiority of males over those of 

 the twenty-five day group, the females being superior in the 

 twenty-five day group as compared with the sixty-five day 

 group. The difference between the two younger groups and 

 the two older ones is not so marked as that for trials or time, 

 but it is nevertheless apparent that the members of the latter 

 covered more ground than those of the former. Yerkes found 

 his older dancers somewhat superior to the younger ones in 

 learning the labyrinth. The writer finds that the younger 'rats 

 learn the maze in fewer trials, that their absolute time is less, 

 their total time and distance are less, and that their speed is 

 greater than in the case of the older rats. His ten month dan- 

 cers were superior to those of one to two months while the 

 twenty-five and sixty-five day rats of this experiment form 



