554 



KARL T. WAUGH 



(18 x 18 cm.). These were interchanged when the food boxes 

 were changed so that the black food box always had a black back- 

 ground and the white box appeared against a white background. 

 The choices during this training were not recorded. 



Upon the completion of the training, changes were made in 

 order to obtain an answer to the questions : does the mouse choose 

 by discriminating between white and black boxes, or is it influ- 

 enced also by the illumination of the whole field? Is food associ- 

 ated with object or with background? For this purpose white 

 cards were placed behind the black box and black cards behind 

 the white. Other conditions were later introduced for testing the 

 nature of the association formed. 



Results 



White box (igainst black background and vice versa 



Uncovered tin boxes used. Backgrounds only changed 



Mouse D was now tried without backgrounds but with the black 

 and white papers on the food boxes. The result of twenty such 

 choices was : 



White box 14 Black box 6 



The next experiment was with plain tin boxes without back- 

 grounds, but with strips of paper (4 cm. x 18 cm.) laid crosswise 

 on the floor of the experiment box directly in front of the boards 

 which carried the electric wires. Black paper was placed on the 

 one side and white on the other. 



Under these conditions mouse O in ten trials crossed over the 

 white paper to reach the tin box nine times, the black paper, once. 



