306 ALDA GRACE BARBER 



matter was not investigated with sufficient thoroughness to 

 obtain conclusive results because of lack of time. Four rats 

 evidently heard the sound and endeavored to locate it, although 

 their attempts were attended with very poor accuracy. The 

 sound apparently had no meaning for the other two animals. 

 The reactions of the first four, fall, in accuracy, between those 

 of control III and those of control V. It seems evident that 

 the quality of the stimulus aids in the present localizing response. 

 Whether the rats can actually localize an interrupted sound more 

 accurately than a continuous one, I am not prepared to say. 

 The issue in the present case may have been one of familiarity 

 vs. unfamiliarity. 



Our attention was next directed to the place of intensity 

 among the essential factors, determining the standard accuracy 

 of response. 



Very loud tapping with the chisel was used to test the effect 

 of strong absolute intensity (con. VII.) The animals were 

 startled and nervous, but their reactions were up to the normal 

 accuracy. A light tapping (con. VIII), was next tried of an 

 intensity not much more than just perceptible to the experi- 

 menter. Here the rats moved more slowly than usual, but 

 maintained an attitude of alert attention. They seemed con- 

 fused and in doubt, though ready to respond. The stimulus 

 may have been below the threshold in some cases with each 

 rat, if the matter is to be judged by aimless wandering during 

 the giving of the stimulus. The accuracy of response was 

 slightly decreased. 



As absolute intensity, within the range used was not the 

 essential factor, relative intensity was tested. What we were 

 striving towards was data which would indicate that the rat's 

 responses were governed by the relative intensity of the sound 

 to its two ears. In the first control (IX) a double stimulus 

 was used, necessitating two operators (Hunter and Barber). 

 Hunter tapped heavily at the allotted section while Barber 

 tapped lightly directly opposite. The tapping was always 

 begun when the rat was half way between Hunter and Barber. 

 The stimuli were given as nearly at the same moment as possible, 

 but the louder one was always slightly earlier in that it was 

 used for a signal for Barber to begin the lighter tapping. Thus, 

 the difference was measured by the length of Barber's reaction 



