AUDITORY SENSITIVITY OF THE WHITE RAT 345 



sandpaper was laid in the alley at the point indicated in dotted 

 lines in the figure. (The rat was to run right for the contact and 

 left for its absence.) The visual stimulus was the same used with 

 the two rats above described. 



The results secured are given in table 3. It will be seen from 

 this that rat 1 failed to substitute the light for the noise. The 

 sandpaper gave 70 per cent correct reactions, which is slightly 

 better than chance but which does not demonstrate clearly that 

 the substitution was made. Rat 7 clearly failed on the sand- 

 paper, but gave slight evidences of substituting the light. The 

 same statements are true of rat 9. Rat 11 failed to substitute 

 the sandpaper. On the other hand, the data on light indicate a 

 clear-cut and all but perfect substitution similar to that in the 

 case of rat 47 described above. 



It is perhaps a safe conclusion that light and noise are more 

 similar for the behavior of rat 11 than are noise and tone, al-. 

 though no direct tests of tone sensitivity were made. The justi- 

 fication for such a conclusion would rest upon the lack of evi- 

 dence for tone sensitivity in the white rat, and upon the behavior 

 of rat 47 above. With all of these rats careful controls indicated 

 that they were not dependent upon the series of presentations> 

 but were guided, normally, by auditory stimuli. 



in 



In the 1917 paper, tests were described in which three rats, 

 7, 15, and 23, acquired the habit of running to the right for hand- 

 claps and to the left for silence. They were then trained to run 

 to the left for a buzzer and to the right for silence. At the close 

 of this second training, when retested on the first habit, no one 

 of the three fell below 80 per cent correct responses for 30 trials. 

 Rat 27 also acquired the two habits serially. Rats 7 and 27 

 were continued in the experiments, to be described in this sec- 

 tion, for the purpose of determining additional features underly- 

 ing their reactions. 



Each of these rats could respond correctly in either of the two 

 following three ways: run right for handclaps (h.c.) and left for 



