harnad@mind.UUCP (Stevan Harnad) (05/13/88)
The following is the abstract of a target article to appear in Behavioral and Brain Sciences (BBS). All BBS articles are accompanied by "open peer commentary" from across disciplines and around the world. For information about serving as a commentator on this article, send email to harnad@mind.princeton.edu or write to BBS, 20 Nassau Street, #240, Princeton NJ 08540 [tel: 609-921-7771]. Specialists in the following areas are encouraged to contribute: psychophysics, sensory physiology, vision, audition, visual modeling, scaling, philosophy of perception Reconciling Fechner and Stevens: Toward a Unified Psychophysical Theory Lester E. Krueger Human Performance Laboratory Ohio State University Columbus OH 43210-1285 ts0340@ohstmvsa.ircc.ohio-state.edu or krueger-l@osu-20.ircc.ohio-state.edu. How does subjective magnitude, S, increase as physical magnitude or intensity, I, increases? Direct ratings (magnitude scales; partition or category scales) can be fitted by the power function, S = aI**b, in which S equals I raised to a power or exponent, b, and multiplied by a measure constant, a. The exponent is typically about twice as large for the magnitude scale (Stevens) as the corresponding partition or category scale, but the higher exponent may be explained by the over expansive way people use numbers in making magnitude estimations. The partition or category scale and the adjusted (for the use of number) magnitude scale for a given modality or condition generally agree with the neurelectric scale and the summated just noticeable difference (jnd) scale. An undue reliance on Weber's law blinded Fechner to the fact that the true psychophysical scale is approximately a power function. Fechner and Stevens erred equally about the true psychophysical power function, whose exponent lies half way between that of Fechner (i.e., an exponent approaching zero) and that of Stevens.