320 



WALTER S. HUNTER 



Control 1. — -When the alley-stops were not used the animals 

 reacted normally. 



Control 2. — -All of the rats failed in their reactions when the 

 whistle was not sounded. This demonstrates clearly that there 

 was some cue involved in the presentation of the whistle stim- 

 ulus that determined the reactions. A reference to table 6 



(appendix) will reveal the fact that I have not included in No. 

 46 's record 30 trials secured with this control during which 

 70% of the reactions were correct. This rat's dependence upon 

 extra-auditory cues was very temporary. This is indicated by 

 the fact that only 50% and 60% were made with control 6 just 

 before and by the further fact that just succeeding the 70% 

 with control 2 the rat fell back to 55% with the same control. 

 I do not know what cue was used during that brief period. 



Controls 3, 4 and 5. — All of the rats succeeded when the 

 noise of rushing air was substituted for the whistle tone. One 

 cannot argue from this that the rats did not hear the tone, 

 although this is a possibility — in fact a probability when con- 

 sidered in connection with the other facts here brought together. 

 Judging from this control alone or in connection with controls 

 4 and 5, an alternative hypothesis is evident, viz., the rats 

 reacted to any auditory stimulus which stood out clearly at the 

 moment of response. An inspection of table 7 (appendix) will 



Control 3 

 Control 4 

 Control 5 



Rat 45 

 Rat 46 

 Rat 47 



Rat 45 

 Rat 46 

 Rat 47 



Rat 45 

 Rat 46 

 Rat 47 



40 trials 

 40 trials 

 70 trials 



40 trials 

 30 trials 

 40 trials 



20 trials 

 50 trials 

 50 trials 



82% correct 

 82% correct 

 77% correct 



80% correct 

 86% correct 

 77% correct 



80% correct 

 80% correct 

 66% correct 



indicate that rat 47 was disturbed slightly at the beginning of 

 each series of tests with control 3. Each time, however, the 

 disturbance quickly passed away. There was less disturbance 

 with control 4. When control 5 was used, there was a complete 

 breakdown at first ; but later on in an isolated test period of 20 

 trials, 85% of correct reactions were made. 



