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Space Constancy on Video Display Terminals
Final rept. 1 Jan-31 Dec 1991
CALIFORNIA UNIV SANTA CRUZ DEPT OF PSYCHOLOGY AND PSYCHOBIOLOGY
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Flicker of video display terminals VDTs has several consequences for visual function space perception is distorted, and reading is slowed. We first tested the hypothesis that the flicker of VDTs interferes with visual space constancy, the perception that the world remains in the same place despite eye movements. Space constancy was probed by moving targets during eye movements, and noting a difference in movement threshold that depended upon whether a target jumped in the same direction as the eye or the opposite direction. Flicker rates up to 260 Hz distorted perception in a direction that implies breakdown of space constancy. Another experiment investigated the roles of color and luminance mechanisms in space constancy. The conclusion was that perception is actively suppressed during eye movements. The suppression depends on channels in the visual system that are insensitive to chromatic differences. Reading with 60 Hz flicker was 3.05 slower than with 500 Hz flicker. The result is consistent with a hypothesis that under flicker the eye parks following an eye movement, until a new sample of text appears. Processing then proceeds in the usual way. The results allow quantitative predictions of reading speed at an flicker rate.
APPROVED FOR PUBLIC RELEASE