AUDITORY SENSITIVITY OF THE WHITE RAT 321 



Rat 46 (table 6, appendix) was only disturbed with the 5th 

 control, and this was speedily overcome — raised from 60% to 

 85%. Rat 45 was not disturbed by either of the three controls. 



The net result of these controls is that the rats are able to 

 respond correctly to two very different noises when these are 

 given in the place of the standard whistle. So far, then, it is 

 certain that although the rats were dependent in their reactions 

 upon the auditory stimulus, this was certainly not of a specific 

 nature. This is in harmony with the data set forth in the two 

 companion papers (Hunter and, Barber, above cited). It was 

 necessary, therefore, to work further in order to show that the 

 tonal element in the whistle was or was not effective. 



Controls 6 and 7. — The only crucial test on the tonal element 

 that could be made with the whistle depended upon ruling out 

 any accompanying noise. There was only one method that 

 was at all feasible. That was to remove the whistle to such a 

 distance that distance itself would eliminate the extraneous 

 factors. Such a test can only be suggestive and never conclusive : 

 (1) It is impossible to tell whether or not the noise has been 

 eliminated for the rat. (2) Distance not only cuts out the noise, 

 but also cuts out overtones and lowers the general intensity 

 of the stimulus. The first is the weighty objection. The second 

 I believe has little or no weight because: (a) from the work on 

 chords cited above and to be cited below (control 10), it is 

 doubtful whether tonal complexity means much for the rat's 

 reactions ; and (b) control 7 indicates that the lowering of general 

 intensity is non-effective. This point is made certain for pure 

 tones, if not for klangs, by (work cited on pp. 219-220 of) the 

 author's previous paper on the auditory sensitivity of the rat. 



The numerical data just given indicate clearly that the rats 

 broke down for control 6. We have just pointed out the possible 

 reasons for such behavior, — the most probable one being the 

 elimination of noise by distance. We must now indicate why 



