LINKING OBJECT BOUNDARIES AT SCALE - A COMMON MECHANISM FOR SIZE AND SHAPE JUDGMENTS

The area over which boundary information contributes to the determinat ion of the center of an extended object was inferred from results of a bisection task, The object to be bisected was a rectangle with two lo ng sinusoidally modulated sides, i.e. a wiggly rectangle, The spatial frequency and amplitude of the edge modulation were varied, Two object widths were tested, The modulation of the perceived center approximat ely equaled that of the edges at very low edge modulation frequencies and decreased in amplitude with increasing edge modulation frequency, The edge modulation had a greater modulating effect on the perceived c enter for the narrower object than for the wider object, This scaling with object width didn't follow perfect zoom invariance but was precis ely matched by the scaling of the bisection threshold with width, stro ngly supporting the idea that the same mechanism determines both the l ocation of the perceived center for these stimuli and its variance, We propose that this mechanism is the linking of object boundaries at a scale determined by the object width.