The Sense of Sight: Brightness Vision 109 



TABLE 10 

 BLACK-WHITE TESTS 



order the possibility of discrimination by position, by odor, 

 and by texture and form of the cardboards. 



The tendency which the dancer has in common with many, 

 if not all, animals to perform the same movement or follow 

 the same path under uniform conditions is an important 

 source of error in many habit-formation experiments. This 

 tendency is evident even from casual observation of the be- 

 havior of the dancer. The ease with which the habit of 

 choosing the box on the left or the box on the right is formed 

 in comparison with that of choosing the white box or the 

 black box is strikingly shown by the following experiment. 

 Five mice were given one series of ten trials each in the dis- 

 crimination box of Figure 14 without the presence of card- 

 boards or of other means of visual discrimination. The 

 electric shock was given whenever the box on the left was 

 entered. Thus without other guidance than that of direc- 



1 No preference tests were given. 



