Date of Award

Winter 1992

Project Type

Dissertation

Program or Major

Psychology

Degree Name

Doctor of Philosophy

First Advisor

Kenneth Fuld

Abstract

Two issues are addressed: One is whether individual differences in psychophysical judgment reflect perceptual differences or differences in subjects' responses, and the second is whether the power law is adequate to describe the perceptions of individual subjects. Six subjects made cross-modal matches and difference matches using weight, finger span, and tone intensities. In order to minimize the chance of obtaining biased responses, number was not used, sessions were spaced far apart, a response continuum was used just once per session, and a set of criteria was adopted to select the best-fitting functions.

Difference matching data were subjected to a multidimensional scaling analysis, then both sets of judgment data were tested for their fit by linear, log, and power functions. Results showed consistency in judgment and characteristics associated with those judgments, including the response function and response range. Results from cross-modal matches showed the power function provided the best fit for all subjects. However, results were inconclusive since it was not possible to ascertain whether a response function was operating--and masking--the form of the psychophysical function. The psychophysical function was linear for half the difference matches and a power function in the other half, leading to the conclusion that individual differences have a perceptual basis, and that while the power law is sufficient to describe group data, it is not sufficient to describe data from all individuals.

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