Home-> All Faculty Members-> Emeritus-> Karen K. De Valois
Karen K. De Valois

694 Minor Hall
(510) 642-7308
AFFILIATIONS Professor Emerita of Vision Science and Optometry; Professor Emerita, Helen Wills Neuroscience Institute

Interactions of color and luminance cues; Analysis of visual motion

The visual system can construct two largely separate maps of the world, using differences in luminance and differences in color as the input information. Although these two maps are quite similar, they are not identical, and the ways in which they vary can signal important characteristics of the visual world. Most of the work in our laboratory examines the ways in which our ability to use color differs from our ability to use luminance, with particular emphasis on the interactions of color and luminance cues when they are simultaneously present. We use psychophysical techniques with human observers.

A primary current focus is on the analysis of visual motion by the luminance and chromatic systems. We have devised objective methods that allow us to compare (and differentiate) the performance of two separate mechanisms that underlie motion perception without resort to qualitative descriptions of perceptual phenomena. Using these tasks, we can determine the conditions under which the luminance system analyzes visual motion in the same manner as does the chromatic system, and we can distinguish the conditions under which it differs. We are now examining the mechanisms that underlie and produce the differences.

We also continue a long-standing interest in general spatial and color vision mechanisms. We are studying the use of spatial information based solely on color differences, the processing underlying color vision, and the spatial code used in object recognition and other high-level perceptual tasks. Although low-level visual coding appears to be based on something like a local spatial frequency analysis, our work suggests that it must be transformed into another (perhaps explicitly spatial) code before perceptual decisions are made.

Selected Publications

Hardy, J. L. & De Valois, K. K. (2002) Color-selective analysis of luminance-varying stimuli. Vision Res., in press.

Takeuchi, T., De Valois, K. K. & Motoyoshi, I. (2001) Light adaptation in motion direction judgments. J. Opt. Soc. Amer. A 18: in press.

Takeuchi, T. & De Valois, K.K. (2000) Modulation of perceived contrast by a moving surround. Vision Res. 40: 2697-2709.

De Valois, K.K. (2000) Seeing. pp 1-392. K.K. De Valois (Ed.) In Handbook of Perception and Cognition. (2nd Edition) M. Friedman & E. Carterette (Series Eds.) San Diego: Academic Press.

Takeuchi, T. & De Valois, K.K. (1997) Motion-reversal reveals two motion mechanisms functioning in scotopic vision. Vision Res. 37: 745-755.

De Valois KK: Spatial vision based upon color differences. (1994) In Lawton, TB (Ed.), Computational Vision Based on Neurobiology. Proc. SPIE 2054: 95-103.

Zhang J, Yeh S-L & De Valois KK: Motion contrast and motion integration. (1993) Vision Res. 33: 2721-2732.

De Valois RL & De Valois KK: A multi-stage color model. (1993) Vision Res. 33: 1053-1065.

Kooi FL & De Valois KK: The role of color in the motion system. (1992) Vision Res. 32:657-668.