The effect of nearby luminance contrast polarity on color boundary localization

Abstract

The study measured the shift in apparent position of a color-defined target boundary as a function of the distance, luminance polarity and amount of contrast of a nearby luminance-defined flanking boundary. In general, the position of the target boundary shifted towards the flank with the attraction being somewhat greater for negative than positive polarity flanks, and for high compared to low contrast flanks. High contrast, negative polarity flanks resulted in greater attraction at 3.69 min arc separation. For low contrast flanks, the apparent shift in position of the target boundary depended on the polarity and position of the flank relative to the target. For example, for small separations (< 3 min arc) flank polarity had little influence, while for larger separations (⩾ 3.69 min arc), negative polarity flanks exhibited attraction while positive polarity flanks began to show repulsion. The results support the notion that luminance and color processing may share a common representation for the localization of boundaries. Position judgments based on this representation appear to be influenced by the amount of luminance contrast in a nearby boundary.