VISION IN THE MOUSE 



553 



the other, and not the sense of smell, check tests were made. With 

 a mouse that seemed to give good evidence of discrimination, the 

 food was placed in the darker box after having been in the lighter 

 for earlier choices. In the case of mouse no. 1, after a training of 

 370 trials favoring the lighter violet, and after the boxes had 

 been washed and clean papers pasted on them, the resulting 

 choices were, in ten trials: 



Light violet (no food) 8 Dark violet (food) 2 



In fig. 2 are given the error curves for the discrimination of inten- 

 sity. The ordinates represent the number of wrong choices in 

 each twenty trials given on a particular day. The succession of 

 days is marked on the axis of abscissas. D and O illustrate 

 experiment (a) ; no. 1 and no. 4 illustrate experiment (b). 



Fig. 2 Error curves for discrimination of light intensity. Ordinates repre- 

 sent number of wrong choices in twenty trials; abscissas represent days 

 ■ , Curve for mouse No. 1. 



, Curve for mouse No. 4. 



„ } (j ur ve for mouse D. 



, Curve for mouse O. 



Experiment (c) Influence of background. 



AIethod : In this experiment two animals, O and D, were used. 

 They were trained for white by one hundred trials, in which the 

 back and sides of the experiment box were covered with cards 



