Oxyopia Abstract

March 23, 2007
Friday, 4:00 PM
489 Minor Hall

Michael Webster, PhD
Professor, Department of Psychology, University of Nevada, Reno
Host: Karen De Valois

Title

Compensatory processes in color vision

Abstract

Color appearance is strongly shaped by adaptation to the observer's color environment. These adjustments may play an important role in maintaining color constancy despite changes in the spectral sensitivity of the observer, and are illustrated both for changes over time (e.g., after cataract surgery) and over space (e.g., at different retinal locations). Conversely, the same processes should lead to differences in color perception when the environment changes, and these are illustrated through measurements of color appearance for individuals living in different environments. Color percepts may be adjusted not only for the average spectrum but also for higher-order properties of the stimulus, for instance calibrating how hue changes with saturation. For example, broadening the bandwidth of a spectrum alters the pattern of cone excitations, yet for lights with Gaussian spectra the perceived hue is independent of bandwidth, suggesting that constant hues are tied to a fixed property of the stimulus (e.g., the spectral peak) rather than a fixed physiological response (e.g., the relative cone responses). This suggests that hue judgments may be largely compensated for the filtering effects of the eye's spectral sensitivity, and that this compensation embodies specific inferences about natural color signals.

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