AUDITORY SENSITIVITY OF THE WHITE RAT 325 



46 and on control 7 for rat 47, the animals were again tested on 

 their ability to turn to the right for the whistle tone. During 

 the interim, the work just described on the fork 256 d.v. was 

 carried on. Whether this could have affected the retention will 

 depend upon the rat's sensitivity to the tone in question. If 

 he can hear the tone, there should at least be no decline in the 

 accuracy of response due to the training on the fork. If, how- 

 ever, he cannot hear the tone, the training upon turning to the 

 right for the fork will tend to break down the normal reaction 

 of turning to the right for the whistle. The results show a 

 decrease in accuracy of response for two rats. Rat 47 reacted 

 normally. These results may be due either to the effect of 

 time intervals or to habit interference. 



Rat 45 Rat 46 Rat 47 



Normal, 90% of 10 trs. 

 Control 11, 90% of 20 trs. Control 11, 100% of 20 trs. Control 7, 80% of 10 trs. 



Retention tests; per cent correct of 50 trials given 

 72% 76% 80% 



VI 



The most significant data secured in the work upon the audi- 

 tory capacity of the white rat may be summarized as follows, 

 (data are here mentioned which were included in the author's 

 previous paper and in Miss Barber's work.) : 



A. Crucial Evidence Upon Tone Sensitivity: 



(1) The tone 256 d.v. sounded on the tuning fork was not 

 discriminated: (a) by 6 untrained rats after 700 trials, (b) after 

 700 trials, by one rat that had learned to react to hand clapping 

 within 400 trials; (c) after 350, 410 and 520 trials respectively 

 by three rats that had been trained previously to respond to 

 hand claps; (d) after 300 trials by 3 rats that had been trained 

 to respond to a whistle. 



(2) The tone 896 d.v. sounded on a tuning fork was not 

 discriminated by 4 untrained rats after 700 trials. 



(3) The chord 512 d.v. plus 640 d.v. sounded on forks was 

 not discriminated; (a) by 2 untrained rats after 650 trials; and 

 (b) after 650 trials by 2 rats that had been trained upon the 



