THE PERCEIVED STRENGTH OF MOTION-DEFINED EDGES

Performance on visual tasks involving the use of motion-defined contou rs is likely to depend on stimulus strength, but presently there are n o empirical or experimental assessments of motion-defined contour stre ngth. Therefore, a matching method was used to estimate the strength o f suprathreshold motion-defined edges on a luminance-contrast scale. T he perceived strength of a motion-defined contour was expressed as an equivalent luminance contrast; this allowed the use of a single scale which accommodates diverse motion-defined stimuli. Motion-defined edge strength estimated in this manner was an inverted U-shaped function o f dot density and dot velocity, and spanned at least a fivefold range of edge strengths. For one observer, maximum motion-defined edge stren gth was equivalent to 79% luminance contrast, at least thirteen times the contrast detection threshold. The results are interpreted via a si mple two-stage model for perceiving motion-defined edges.