DISCRIMINATION OF SIZE AND FORM IN THE RAT 



311 



The author is indebted to Professor John B. Watson for 

 helpful suggestions and criticism, and to Miss Cora D. Reeves 

 for the data in experiment n and for valuable assistance in 

 other parts of the work. 



APPARATUS AND METHODS 



Throughout the greater part of the experimental work a 

 discrimination box, modified after the type designed by Yerkes, 

 (1907), was employed. This box was used by Hoge and Stock- 

 ing, (191 2). A diagram of it is given in figure 1. The box con- 



Figure 1. Discrimination box. a, Starting compartment; b, sliding door; c, dis- 

 crimination compartment; d, d', passages wired with electric grill; e, door 

 to food compartment; f, light compartment; g, food compartment; h, 

 reversible frame containing the translucent forms used as stimuli, ^j^j Juj 



