Abstract
The detection sensitivity of Gabor (target) is improved when two high contrast flanking Gabors (flanker) have the same properties; orientation, phase, or color on the cone-opponent (cardinal) axes. This effect is called Collinear Facilitation (CF). It is still unclear whether CF occurs in different hue combination of the target and flanker. We investigated the hue selectivity of CF for Gabor stimuli defined on isoluminant plane of the DKL color space. Chromaticity of Gabor was defined in four hue directions; two cardinal axes (0–180, 90–270 deg) and two intermediate axes (45–225, 135–315 deg). The stimulus was composed of three Gabor patches; the target was at the center, and others were the flankers. Detection thresholds was measured by two interval forced choice, while the target contrast changed by 1-up 2-down staircase procedure. We also measured threshold without flankers, and derived threshold ratio by dividing threshold with flanker by that without flankers. Results showed that the CF occurred mostly in 0–180 deg direction in the present study. The threshold decreased when the flanker hue was similar to the target hue, except 90–270 deg target; the threshold ratio of 90–270 deg target had a large individual difference and the average showed a slight decrease. The decrease showed two features; the effect was remarkable with 0 deg flanker for 0 and 45 deg target conditions and with 135 deg flanker for 90 and 135 deg target conditions. These results suggest that the CF has a broad chromatic selectivity but was limited along cardinal-axis directions.