PUNISHMENT AND REWARD AS MOTIVES 45 



which were connected with a Porter inductorium. A convenient 

 switch enabled the operator to cause the current to flow either 

 through W or W. Two Columbia dry cells No. 6 furnished 

 the primary circuit. The position of the secondary coil was 

 fixed at 7 cm. The stimulus lights consisted of two un- 

 calibrated carbon lamps, 115 D. C, of 2 and 16 c. p. respec- 

 tively, placed in the light compartments C and C. The par- 

 tition separating B from C contained two standard stimulus 

 plates, S and S', 5.5 cm. in diameter, placed 25 cm. between 

 centers. The distance between the center of the plate and the 

 floor of the box was 10 cm. Both plates were covered with 

 flashed glass as recommended in the report of Yerkesand Watson. 1 



The tests were made upon light-adapted animals in a room 

 the general illumination of which barely sufficed to show the 

 movements of the animals. 



Six female rats were used in the experiment. Five of them, 

 Nos. 1, 3, 5, 7 and 9, were hybrid, and all from the same litter. 

 Nos. 1 and 5 were albinos; 3, 7 and 9 were black-and-white 

 rats, with pigmented eyes. No. 11 was a pure white rat from 

 another litter. Preliminary experiments were begun upon the 

 rats when they were 49 days old. All the rats were allowed 

 to explore the experiment box for two days before preference 

 tests were begun. In conducting the preference tests, 10 trials 

 a day were given each rat. The experimental conditions of 

 the preference tests were made the same for all the animals. 

 At every trial food was placed in a small dish in each of the 

 alleys V and V. The lights were interchanged frequently and 

 at irregular intervals, in order to exclude choice by position. 

 The two lights occupied the two positions left and right an 

 equal number of times. The two lights are designated, the one 

 as b (brighter, 16 c. p.), the other as d (darker, 2 c. p.). 

 Table I shows the record of the choices made by the animals. 



From this table it will be seen that two rats had no preference ; 

 that one had a slight preference for the darker compartment, 

 whereas three showed a preference for the brighter of the two. 



In accordance with the generally accepted method of training 

 against a preference, those rats which had been found in the 

 preliminary tests to choose the brighter of the compartments, 



'Methods of studying vision in animals. Behavior Monographs, No. 2, 1911. 



