18 



relation of age to the learning ability was as follows: 



One week preceeding the day on which the animal was to 

 begin work, food waa removed from the living cage and the rat 

 was fed each day in the center of the maze v.'hich waa temporari- 

 ly jartitioned off from the remainder, making it imj osaible for 

 him to roam at will through the maze. The first day, he was 

 allowed to eat for forty-five minutes; the second day, for 

 thirty minutes; the third day, for twenty minutes. The feed- 

 ing tine was then diminished five minutes on each succeeding 

 day, 30 that the day before beginning the problem, the rat had 

 been fed for five minutes in the food box of the maze. Tv;o 

 things were accomplished by this procedure - lat : The rat was 

 rendered quite hungry, a necessary stej , since food was the 

 stiniilus used, but the shock which would have resulted from en- 

 tire absence of food v/as avoided. 2nd: It becane accustomed 

 to some extent to exi^erimeatal conditions. 



On the day when the problem was actually begun, the tem- 

 porary partition was removed from the maze, a dish of milk- 

 soaked bread placed at the center and the rat placed in the 

 starting box (3. B. Plate 1]. The instant it emerged into the 

 maze proper, the door (indicated but not shown in the illustra- 

 tion} , was closed behind it making return into the starting 

 box impossible, the stop watch was started and the tracing be- 

 gun. TTwelve or fourte'3n minutes might be required to reach the 



1. Grain was given in the cage each day at tlie orA of the feed, 

 ing period. 



