Abstract
A number of studies have shown that visual attention modulates performance for various visual tasks (e.g. contrast detection). The visual attention seems to facilitate or inhibit higher-level processes of visual information. However, it has not been clear yet to what extent the visual attention modulates processes in early vision. The present study aims to reveal whether the visual attention affects luminance and chromatic contrast sensitivities in a different manner. Contrast sensitivity functions were measured in foveal vision (the central task). The peripheral stimulus was also presented simultaneously at one of 8 peripheral locations in 10 deg eccentricity. The observer reported the stimulus location (the peripheral task). In this dual task paradigm two conditions were set, central priority and peripheral priority conditions. The observer gave more priority to the central task than to the peripheral task in the central priority condition (the attended condition), and vice versa in the peripheral priority condition (the unattended condition). It was found that sensitivity decrement was larger in chromatic than in luminance contrast in the unattended condition. Our results might suggest that visual attention influences early visual processing pathways.