222 WALTER S. HUNTER 



the tones than if they had been continuously sounded. Inas- 

 much 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. Further experimentation alone will 

 determine whether sensory defect is the reason for neglecting 

 all of the tones given here. Such an explanation certainly seems 

 necessary for the lack of sensitivity to c' 512. ^ 



At the present, the above work is being extended in three 

 directions: (1) Search is being made throughout the pitch scale 

 for a tone to which the rats will respond. Both continuous 

 and interrupted tones will be used. When an effective tone is 

 found, the original problem will again confront us, viz., can 

 rats hear noise and tone as distinct experiences. (2) Miss Bar- 

 ber's work will probably throw added light upon the question 

 of relative sensitivity to noise and tone. (3) Mr. A. C. Scott 

 is beginning tests which are expected to emphasize the relations 

 between vision and hearing with respect to the learning pro- 

 cesses involved. One problem with which he will deal will be 

 this: Is the simultaneous presentation of stimuli, such as is 

 used in visual discrimination, more favorable to learning than 

 a successive presentation of stimuli, such as must be used in 

 auditory discrimination work? 



One additional matter needs comment. So far as I have 

 been able to ascertain there are no published studies on the 

 anatomy of the white rat's ear. I am supported in this state- 

 ment by several eminent authorities. In view of the results 

 above presented, it is at least possible that careful anatomical 

 studies might throw light upon the structural basis for the 

 perception of noise and tone. 



» Johnson's work >» has appeared since this paper went to press. On pp. 44^5, 

 the author reports negative results at the conclusion of 150 trials on mere sensitivity 

 to a tuning fork of 256 d. v. The suggestion is made from this that in ordinary 

 noises the dog may reach only to high overtones. 



'» Johnson, H. M. Audition and Habit Formation in the Dog. Behavior Mono- 

 graphs, 2, no. 3, 1912. 



