3 

 the inclined plane "bos. All three problems have been 



previously used in animal behavior, in similar or modified 

 forms. Hone of them can be said to be difficult problems 

 to learn. 



The latch box (Fig.l) was a bo:-: frame about 2 8 c,m. 

 square and i be lower left hand corner of one side was 

 a door, 15 Q.om.. o^ 18 c.m.- The box, as rell as the door, 

 was covered with wire netting. A wooden latch was at- 

 tached to the frame work of the box and this fitted in a 

 nottfh on the door. Inside of the door was a light spiral 

 spring which opened the door when the latch was released 

 and also held the latch more firmly in its notch, as a 

 result some pressure was required to push the latch up- 

 ward. V/hen the latch was raised the door would open, 

 springing inward. The box was placed om a table. To 

 avoid an undue amount of curiosity on the part of the 

 rat a, and, as far as possible, to re-establish conditions 

 of cage life, the box was covered with a wire hood. One 



