The Sense of Hearing 83 



My assumption, on the basis of extended study of the ability 

 of the dancer to profit by experience, was that if it could 

 hear the sound of the bell it would soon learn to avoid the 

 box-that-rang and enter instead the one which had no sound 

 associated with it. 



Systematic tests were made with No. 4 from the 3d to 

 the 1 2th of February, inclusive, 1906. Each day the 

 mouse was permitted to find his way to the nest-box through 

 one of the small boxes ten times in succession. Usually the 

 experimenter rang the bell alternately for the box on the 

 left and the box on the right. The time required for such a 

 series of experiments varied, according to the rapidity with 

 which the mouse made his choice, from ten to thirty minutes. 

 If in these experiments the animal approached and entered 

 the right, or soundless box, directly, the choice indicated 

 nothing so far as ability to hear is concerned; if it entered 

 the wrong, or sounding box, despite the ringing of the bell, 

 it indicated either the lack of the influence of experience or 

 inability to hear the sound; but if it regularly avoided the 

 box-which-sounded it thus gave evidence of ability to hear 

 the sound of the bell. The purpose of the test was to deter- 

 mine, not whether the mouse could learn, but whether it 

 could hear. 



For ten successive days this experiment was carried on 

 with No. 4 without the least indication of increasing ability 

 to avoid the wrong box by the association of the sound of 

 the bell with the disagreeable electric shock and failure to 

 escape to the nest-box. In fact, the experiment was dis- 

 continued because it became evident that an impossible task 

 had been set for the mouse. Day by day as the tests were in 

 progress I noticed that the animal became increasingly afraid 

 of the entrances to the small boxes; it seemed absolutely 

 helpless in the face of the situation. Partly because of the 



