Thresholds at luminance edges under stabilized viewing conditions

Increment thresholds were measured for a small, briefly presented test line as a function of distance from a high-contrast abrupt luminance edge. The experiments were carried out under both stabilized and unstabilized viewing conditions to determine the role of eye movements in the "edge threshold effect." It was found that the edge threshold effect (i.e., the rise in threshold at the luminance edge) was less pronounced under stabilized conditions. We conclude from this that a significant portion of this effect is mediated by the temporal transients that are brought about by eye movements. Little difference is found between stabilized and unstabilized conditions when the background is briefly presented. Narrow bright bands appear on the bright side of a sharp edge for unstabilized viewing, but disappear under stabilization.