COLOR AND LUMINANCE INTERACT TO IMPROVE PATTERN-RECOGNITION

The authors have previously hypothesised that colour vision has evolve d not only to encode colour per se but also, perhaps principally, to e nhance luminance-based visual processing, so that far colour informati on to be fully effective, luminance as well as chromatic variations sh ould be present in visual targets. Results of previous experiments, te sting detection of spatial gratings and detection and perceived bright ness of Mach bands support the hypothesis. Further experiments are rep orted in which the hypothesis was tested by using a higher-level task of pattern recognition. Subjects had to discriminate between luminance (isochromatic), isoluminant (chromatic), or combined colour/luminance ellipses and circles. It was found that the ability to discriminate b etween a circle and an ellipse was greatly enhanced when both colour a nd luminance variations were present as compared with the pure luminan ce or colour presentations. Summation-square analysis shows linear col our-luminance summation which can be modeled by a single-analyser mode l.