THE SPATIAL REGION OF INTEGRATION FOR VISUAL SYMMETRY DETECTION

Symmetry is a complex image property that is exploited by a sufficient ly wide range of species to indicate that it is detected using simple visual mechanisms. These mechanisms rely on measurements made close to the axis of symmetry We investigated the size and shape cf this integ ration region (IR) by measuring human detection of spatially band-pass symmetrical patches embedded in noise. Resistance to disruption of sy mmetry (in the form of random phase noise) improves with increasing pa tch size, and then asymptotes when the embedded region fills the IR. T he size of the IR is shown to vary in inverse proportion to spatial fr equency; i.e. symmetry detection exhibits scale invariance. The IR is shown to have rigid dimensions, elongated in the direction of the axis of symmetry, with an aspect ratio of ca. 2:1. These results are consi stent with a central role for spatial filtering in symmetry detection.