Susan M. Heidenreich

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We evaluated the hypothesis that smooth pursuit eye movements affect speed discrimination thresholds of distal stimuli because they alter the retinal image speed. Subjects judged speed differences of sine-wave gratings while they simultaneously pursued a superimposed moving bar. Speed discrimination thresholds were measured, under conditions of controlled(More)
Eye movements add a constant displacement to the visual scene, altering the retinal-image velocity. Therefore, in order to recover the real world motion, eye-movement effects must be compensated. If full compensation occurs, the perceived speed of a moving object should be the same regardless of whether the eye is stationary or moving. Using a pursue-fixate(More)
To determine whether speed discrimination improves when the retinal image is stabilized against the effects of eye movements, thresholds were measured under stabilized and normal viewing conditions. In the normal viewing conditions, eye movements were recorded and used to estimate retinal-image speeds. Stimulus reference speed for sinusoidal gratings varied(More)
Spatially sampled motion (H.P. Snippe & J.J. Koenderink, 1994) leads to time-lagged correlations of luminance change at discrete spatial positions. Observers matched the perceived width of a bar whose motion path was sampled spatially to the width of a static bar; the width of the moving object was not directly observable. Observers did reasonably well on(More)
Three experiments tested whether motion information for nonequiluminant (luminant) and equiluminant dots affects direction judgments when both types of stimuli are moving simultaneously in the same display. The motion directions for the two sets of dots were manipulated to produce four direction differences (0 degrees, 30 degrees, 60 degrees, and 90(More)
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