324 . WALTER S. HUNTER 



marily with the first intention, it was thought advisable to 

 extend them in the light of the second. 



In the work published in volume 4 of this Journal, rats that 

 had responded to noise by turning to the left were later given 

 from 350 to 520 trials in an endeavour to force them to turn 

 to the right for the tone 256 d.v. sounded on the fork. No one 

 of the rats showed improvement during this interval. 



In the present instance rats 45, 46 and 47 had been trained 

 to react successfully to the whistle by turning to the right. 

 They were then given a series of tests with the tuning fork 

 256 d.v. in an attempt to train them to turn to the right for the 

 fork tone also. A new series of presentations was employed 

 as follows : 



rllrrrllrl Three hundred trials were given; but there was no 

 rrlrllrllr improvement in the reactions from first to last. The 

 lrrlrrlrll following table is a summary of this fact. These re- 

 Urlrrlrlr suits lend further indirect confirmation to the con- 

 clusion drawn above that the rats were depending upon noise 



TABLE 5 

 Trials 



Rats 



45 46 47 



50 25 28 27 



100 26 32 28 



150 29 28 28 



200 29 28 27 



250 25 23 27 



300 27 31 31 



in the whistle complex and not upon tone. The present results 

 are also very striking when we compare them with the rat's 

 ability to react to noises which are very dissimilar, from the 

 experimenter's point of view, to those with which it has been 

 trained. To quote from the previous paper, pages 221-222, 

 "All of the tones given were for some reason very different 



from the noises Inasmuch as the animals reacted 



in the same manner to all of the noises, it is certainly a striking 

 fact that none of the tonal stimuli given were classed as noises." 



V 



Retention Tests. — Forty-one days (for rats 46 and 47) and 

 45 days (for rat 45) after the tests on control 11 for rats 45 and 



