LOCALIZATION OF SOUND IN THE WHITE RAT 301 



thorough study of the factors governing these curve differences 

 has not been made at the present time. 



The length of the periods of learning the auditory localization 

 in our problem are interesting when compared with an exper- 

 iment on the effect of using food as the stimulus object performed 

 by Mr. A. C. Scott in this laboratory. He had two problems 

 for comparison. In one the rats set up an association between 

 the appearance of a light in one of two boxes and being fed at 

 a point immediately over the light, i. e., a problem in which 

 the animal learned to eat the light stimulus, we might say. 

 This is comparable in every way with our problem in which 

 the rats "ate the auditory stimulus" in so far as they understood 

 the problem. The association in Mr. Scott's experiment was 

 learned in 30 trials, the best of our rats learned in from 40 to 

 64 trials. In Mr. Scott's second problem, the rats were trained 

 in the same Yerkes discrimination box to respond to the presence 

 or absence of light by running in the proper direction through 

 the box. The food was placed in the rear of the home box from 

 which they started. This association was learned in not less 

 than 120 trials. It seems reasonable to conclude, therefore, 

 that one large factor making for rapid learning in our tests 

 was the use of the food object for the stimulus. There are two 

 other possibilities which would need to be seriously considered 

 in an exhaustive study of this matter. The localization of 

 sound may be largely an instinctive capacity; or it may be a 

 capacity which was considerably developed in the ordinary life 

 of the animal before the present tests were begun. 



The learning of the association between source of sound and 

 getting food fell into four main stages. In the first few trials, 

 the rats apparently disregarded the auditory stimulus while 

 seeking for some other cue as a guide. Visual (?) cues were 

 used predominately, i. e., the appearing of the hand over the 

 side of the box with food (this occurred only after the rat had 

 made the reaction of standing up at some point) , and movements 

 of the screen. Olfactory cues seemed to be sought, for the rat 

 frequently sniffed in all directions before responding. In the 

 second stage, an awareness of the tapping was evidenced. This 

 was indicated by a quick onward start when the stimulus was 

 given. However, the animal did not seem to realize that this 

 was a cue to the correct direction of the food, merely that it 



