Oxyopia Abstract

May 24, 2002
Noon
489 Minor Hall

Carol M. Cicerone, PhD
Department of Cognitive Sciences, University of California Irvine
Host: Marilyn Schneck

Title

"From cones to color perception: What good is color vision anyway?"

Abstract

The presentation will focus on two areas of color vision. First, experiments aimed at uncovering the relative numerosity and spatial arrangement of long-wavelength-sensitive (L) and middle-wavelength-sensitive (M) cones in the living human eye will be described. In the central fovea, estimates were obtained from hyperacuity performances of observers for the full and the separate L and M cone submosaics using 2-dot chromatic stimuli on cone-selective adapting backgrounds. In the peripheral retina, estimates were obtained from red-green color naming (eleven-point scale, ranging from 100% red to 100% green) of a small test flash (0.86 min of arc, 555 nm, constant intensity) presented at different locations (grid with 1.5 min of arc steps) centered at 17 deg temporal eccentricity. In both cases, simulated performances, based on an ideal observer model, were generated for different mosaics composed of varying L and M cone relative numerosity and spatial configuration. The best match between the simulated and measured performances determined the solution mosaic. Each observer's solution mosaic contained more L than M cones, randomly arrayed over these retinal regions. Second, experiments aimed at understanding the role of color vision in organizing natural scenes will be described. In an effect we call color from motion, apparent motion is accompanied by subjective color spread seen in physically achromatic regions. We report that chromatic differences alone, in the absence of luminance differences, can produce subjective color spread linked to apparent motion, suggesting that color, independent of contour, can be recovered in tandem with seeing motion. We show that depth can also be seen in conjunction with seeing motion. Multiple frames of a novel stimulus are binocularly presented, with all aspects, except color, of the binocular images identical. In still view, rivalry occurs due to the unmatched color of some corresponding image elements in the two eyes. When frames - created by translating color assignments, and nothing else - are rapidly cycled, a colored object is seen moving in depth. In natural scenes, the same mechanisms may be used to reconstruct the depth, color, and form of hidden objects so that they can be seen as if in plain view.

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