Sensory Discrimination: Hearing 133 



Barber's (19) experiments on the white rat's ability to 

 localize sounds : noises, such as those made by tapping on 

 wood, were localized within an average limit of error of 

 from two to four inches, but tuning-fork and organ-pipe 

 tones were wholly ignored. 



The experiments of Johnson (384) on the dog's ability to 

 discriminate tones and noises gave results very similar 

 to these of Hunter on the rat, and furnish an illuminating 

 commentary on certain difficulties in experimentation on 

 animals. Zeliony (839), working by the salivary reflex 

 method described on page 57, had reached the conclusion 

 that the dog can discriminate between tones whose pitch 

 differs by only a quarter of a tone. Kalischer (388), whose 

 interest lay in testing the work of Munk 1 on the localization 

 of the central terminations of the sensory pathways for 

 tone in the temporal region of the cortex, succeeded in 

 training dogs, with and without temporal lobes, to snap 

 for food when one tone was sounded and inhibit reaction 

 when a tone of considerably different pitch was given. 

 Rothmann (646 a) and Swift (699) also observed discrimina- 

 tion of tones in the dog, and Kalischer (388) claims for the 

 dog memory of absolute pitch. But the experiments of all 

 these investigators, including those who used Pawlow's 

 method, suffer from the fatal defect that the experimenter 

 was in the room with the animal tested, and hence might 

 have presented other clews, by making slight involuntary 

 movements, which could act instead of the tones to guide 

 the animal's choices. How serious this objection is appears 

 from Johnson's own results. His dog subjects all learned to 

 discriminate between a tone of 256 double vibrations and 

 one of 384 double vibrations, an interval of a fifth, whether 

 the tones were sounded on tuning forks or on a wind appara- 



1 Munk, H., 1890. Ueber die Funktion der Grosshirnrinde. Berlin. 



