III. METHODS OF THE EXPERIMENT 



THE first maze employed was designed by Professor Cattell, the 

 plan of which is shown in Fig. 1. The animal has, in the first com- 

 partment, the alternative between two gates, one of which can be 

 pushed open, while the other is locked, with an identical situation 

 in a second compartment. The path that the animal must follow 

 can be altered by varying the position of the open gates. "Unit 

 construction" is used in the dimensions, which are adjusted to the 

 size of the animals used, and which permit the addition of any de- 

 sired number of standard units. 



Preliminary tests were made with albino rats, but later mice, 

 which are more active and more easily handled, were substituted. 

 The mice were given one trial each day at as nearly the same time as 

 possible. Light was found to play but a minor role in the tests, day- 

 light and artificial light serving equally well. At the outset the age 

 of the mice when first tested was not always known, but later, when 

 the various litters were obtained, the young mice were tested at, or 

 about, the age of four weeks. 



The mice were rewarded for a successful trial by a mixed diet of 

 milk, bread, oatmeal and sometimes meat. A little dry bread was 

 always in their cages. Besides satisfying their hunger, the mice had 

 the additional reward of a place to exercise and the companionship 

 of the mice that had just been tested. The order of the tests was 

 varied day by day. In case the way through the maze was not found 

 in 360 seconds the animal was removed and tested again the follow- 

 ing day. The maximum record for a single trial is 360 seconds. 



