296 ALDA GRACE BARBER 



Length of sides of stimulus board 10 1/2-11 1/2 in. 



Width of stimulus board 3 in. 



Height of stimulus board from table 3 1/4 in. 



The box had inevitable defects. (1) The fact that no release 

 box was used allowed the rat to wander at will, getting the 

 stimulus from different angles and positions. No constant 

 standard head position could be gotten. (2) The reflection of 

 the sound probably differed as the rat was nearer to the center 

 or to the side of the box. Finally, (3) the sound might be 

 diffused along the boards and thus prevent very accurate local- 

 ization. However, in spite of these defects, the localizations 

 were quickly and comparatively accurately made. 



Various methods suggest themselves by which a relatively 

 better control of the position of the rat with respect to the 

 point of origin of the sound could be obtained. This of course 

 is one important feature necessary for a comparison of animal 

 experimentations with the human work in the localization of 

 sound so far accomplished. Perhaps Pawlaw's salivary method 

 would offer the best solution of the difficulty in tests with such 

 animals as are suited to the method. The animal's head here 

 could be fixed in a stationary position during the test. Pre- 

 sumably, after the association of a definite localization of the 

 sound stimulus with food had been set up, the animal could 

 be tested for the accuracy of change of localization in the different 

 planes. This accuracy would be measured in respect to the 

 quantity and quality of the flow. Monaural hearing should 

 be tested here also. 



Stimuli — The standard instrument for giving the stimulus (a 

 tapping upon the stimulus board) was a medium weight chisel, 

 the tapping of which had a predominant pitch between 256 

 d. v. and 512 d. v. This was determined by the use of Helm- 

 holtz resonators. Other stimulus sounds were made by: (1) 

 tapping upon the stimulus board with the rubber of a lead 

 pencil; (2) sounding a 256 d. v. tuning fork outside the screen; 



(3) giving the interrupted tone, 256 d. v., on an organ pipe; 



(4) hissing through the teeth; and (5) tapping with a lead pencil 

 rubber upon the resonator box of a 256 d. v. fork. In giving 

 this last stimulus, the resonator box was held in the hand outside 

 the screen, and was tapped on the upper surface 1/4 of the 



