AUDITORY SENSITIVITY OF THE WHITE RAT 



341 



TABLE 1 



Percentage of correct responses in each succeeding 50 trials 



tion. The controls are therefore not conclusive, although the 

 indication is that tone sensitivity is absent. The following 

 controls were used with rat 3 : 



Control 1. The noise stimulus ordinarily used only for turning to 

 the left was used for all trials. This substituted a certain "thud" for 

 the "tone and thud" previously used as a cue for turning to the right. 

 No tone therefore was given. All other conditions normal. The re- 

 sponse was counted correct if it coincided with the order of presentation. 



Control 2. The supports of the tuning fork were fastened to tripods 

 resting upon the floor and in some cases upon two adjacent tables. This 

 control ruled out the possibility of contact cues due to the transmission 

 of vibrations through the table to the discrimination box. 



Control 3. Cotton was forced between the prongs of the fork. Strik- 

 ing the fork now produced a faint tone of high pitch as well as a noise 

 of new quality. The same stimulus from striking the fork was given in 

 each trial. The reactions were counted as correct if they fitted the 

 series of presentations. 



Control 1 caused a breakdown in the rat's high percentage of 

 correct responses. When this control was alternated with nor- 

 mal conditions on intervening days, correct responses did not 



