Theory of the Neural Quantum in the Discrimination of Loudness and Pitch

Abstract

The authors present evidence from 2 expts. (discrimination of auditory intensity and of frequency) which indicate that the relationships investigated are best described by the rectilinear functions demanded by the quantal theory. Because of the relatively large over-all fluctuation in sensitivity, in order to test the quantal theory directly it is necessary to present the standard and comparison stimuli in close temporal succession. The apparatus by which this was accomplished is descr. Rectilinear functions were fitted to 15 sets of data from the frequency discrimination expts. by the method of least squares, and the phi-function of [gamma] was fitted to the same data by Urban''s tables. The chi-square test of goodness of fit was applied and the P-values detd. The P-values favor the quantal hypothesis; the composite coefficient for the phi-function of [gamma] was .008, for the rectilinear function .931. The size of the quantum does not remain unchanged under all conditions, and it is necessary to make detns. in the same exptl. session. When the results obtained in several sessions are averaged, the psychometric function tends to assume the sigmoid form. The measure of differential sensi-sensitivity in audition is 2 quanta.