Spatial frequency response and perceived depth in the time-course of object superiority

Abstract When a target consisting of a briefly flashed diagonal line segment is combined with a set of auxiliary lines (the context pattern) to yield the perception of a three-dimensional object, it can be identified more accurately than when the context pattern yields a flatter perception. This is the objectsuperiority effect ( Weisstein and Harris, 1974 ). The present experiments utilized three context patterns that yielded significantly different ratings of perceived depth. Observers judged which of four target lines was presented; the line was alone or was accompanied by one of the three context patterns. The context pattern appeared simultaneously or followed the target by a delay of 30–270 msec. Spatial frequency response was varied by presenting the stimuli in the retinal periphery or by blurring them, thus diminishing visual response to high spatial frequencies. Just the target line was blurred, or just the context pattern, or both. Results showed that blurring just the target, blurring both stimuli, or presenting them in the retinal periphery all had similar effects on the temporal functions of accuracy versus delay of the context pattern (metacontrast functions): the functions for the patterns rated higher in depth became more like those for the flat pattern. When just the context pattern was blurred the results were different: the functions for the pattern rated flat became more like the three-dimensional ones. These results were closely related to the way depth ratings changed as the context patterns, target lines, or both were blurred. Our findings suggest that the visual channels that respond to high and low spatial frequencies also have different temporal responses to apparent three-dimensionality.