LUMINANCE AND EDGE INFORMATION IN GROUPING - A STUDY USING VISUAL-SEARCH

Preattentive grouping is supported by 2 systems, a brightness system t hat is contrast polarity sensitive and an edge system that is relative ly insensitive to contrast polarity. Search was spatially parallel for pairs of same contrast polarity vertically aligned circles, among hor izontal pairs, and serial for pairs of circles that had the opposite c ontrast polarity (Experiments 1-3). By replacing the circles with squa res, the authors investigated the effect of adding collinear edge info rmation. When collinear edges were present, the polarity difference be tween paired items did not disrupt grouping (Experiments 4-6). These r esults support models of grouping in which brightness and edge informa tion are processed separately (e.g., S. Grossberg & E. Mingolla, 1985) and models of visual search in which complex relations between stimul i can be computed in parallel across the display.