AUDITORY SENSITIVITY OF THE WHITE RAT 317 



alternation between the two alleys. For example the series 

 llrrllrrlr is given and the animal chooses as follows lrlrlrrlr. 



The reaction is 70% correct and yet there is only one reversal 

 (underscored) of the series of alternations. Again the series 

 rllrrrlllr is given and the rat alternates with no reversal making 

 60% correct. Another rat given this latter series alternated 

 regularly save that on the 3rd, 4th and 5th trials he went to 

 the right hand box. In the regular series (on learning), there 

 were more reversals and there was also a marked tendency to 

 reverse after each success only. Inasmuch as this last type of 

 behavior was not present when punishment and the end-stops 

 were not used, it seems probable that these factors produced 

 the behavior by modifying the simple alternation position habit. 



The moral of these controls lies in pointing out the necessity 

 of being on one's guard against complex position habits which 

 otherwise might be taken as evidence of discriminative ability. 



Many tests in comparative psychology which have been in- 

 tended primarily as tests of discrimination have been vitiated 

 because they have required the animal to localise the stimulus 

 in order to give evidence of sensitivity. Hence when negative 

 results are secured it is not known whether the animal was 

 insensitive or whether it was simply unable to localize the stim- 

 ulus. The method adopted in the present tests does not involve 

 a localization factor (Johnson's work has this merit also.) 3 

 Hence the negative results secured when working with the pure 

 tones 256 d.v. and 896 d.v. and with the chord 512 d.v. plus 

 640 d.v. are of great significance. 



111 



Learning Whistle— Tests were now begun on four . untrained 



rats (Nos. 44, 45, 46 and 47) using as a stimulus 3906.17 d.v. 

 on a Galton whistle. The whistle was held in clamps above 

 the experiment box where the forks had been and was turned 

 in such a manner that air currents were not directed downward 

 upon the animals. It was sounded by blowing (with the ex- 

 perimenter's mouth) through a long tube. The standard inten- 

 sity of this tone, when measured with a water manometer, was 

 secured with a pressure of 16 cm. We may call this whistle, 



3 Johnson, H. M. Audition and Habit Formation in the Dog. Behav. Mon. y 

 vol. 2, no. 3 1913. 



