Present possibilities for auditory theory

The authors roughly divide auditory theories into resonance and telephone theories; the former holding that pitch is a function of the particular nerve fibers excited, and intensity is correlated with number of impulses in nerve response; the latter holding that frequency of response in nerve is directly correlated with frequency of sound waves, and intensity is a function of spread of excitation among fibers. The present evidence favors the resonance hypothesis. Two recent experimental attacks are (1) that of Forbes, Miller, and O'Connor, on decerebrate cats, in which auditory stimulations were picked up from electrodes applied to the medulla, and recorded by galvanometer, and (2) that of the authors, who substituted a telephone receiver for recording, to catch currents of high frequency. Forbes, studying low frequencies, concludes in favor of resonance, since he interprets his frequency correlation to be with intensity of excitation. The authors, however, find frequency in the nerve response to correlate with frequency, not intensity of stimulation. This finding rules out the Helmholtz theory as currently stated. The remaining possibilities, then, are: (1) a resonance-telephone theory, combining both principles, (2) a non-resonance-telephone theory, like Boring's, (3) a resonance-volley theory, formulated by the authors, which "would include the chief features of the resonance-telephone theory, and yet fall in line with the Adrian intensity-frequency principle, and the usual assumption that refractory phase in auditory nerve is of the same order as that in other sensory nerves," and (4) a non-resonance-volley theory, requiring the assumption of central analysis. All are, according to the authors, equally possible.