On the “Psychophysical Law.”

Abstract

In recent years, S. S. Stevens revitalized the discussion concerning the growth of sensation as a function of stimulus intensity by showing that the relationship can be described more adequately in terms of a power function suggested by Plateau than in terms of a logarithmic function derived by Fechner. The power function applied by Stevens to various sense modalities holds at medium and high sensation levels. At near threshold intensities, it appears to deviate from empirical data. Attempts have been made to correct the discrepancy by adding a constant in the intensity domain. It is shown that such a correction is inadequate and that an additive constant on the sensation continuum produces a better approximation of the experimental data. The derivation of the mathematical expression is followed by examples in which experimental and theoretical data obtained under various psychophysical conditions are compared. (Work supported by a contract between the Office of Naval Research and Syracuse University.)