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Frederick Kingdom, Jason Bell, Gokhan Malkoc, Elena Gheorghiu; Chromatic variations suppress suprathreshold brightness variations. Journal of Vision 2010;10(7):384. doi: https://doi.org/10.1167/10.7.384.
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© ARVO (1962-2015); The Authors (2016-present)
Aim. To determine the relative perceptual saliencies of suprathreshold color (chromatic) and luminance variations when the two are combined. Method. The stimulus was similar to that used by Regan & Mollon in their study of the relative saliencies of the cardinal color directions (in Cavonius, ed., Colour Vision Deficiencies XIII, 1997). It consisted of left- and/or right-oblique modulations of color or luminance defined within a lattice of circles, with each circle ringed by a black line to minimize any impression of transparency when the different modulations were combined. There were two conditions. In the ‘separate’ condition, the color and luminance contrasts were presented separately in a 2IFC procedure and the subject indicated on each trial the interval containing the more salient modulation. In the ‘combined’ condition, the two modulations, which were orthogonal in orientation, were added together and the subject indicated on each trial whether the dominant perceptual organization was left or right oblique. For each color direction and for each condition, the relative color to luminance contrast at the PSE was calculated. Results. For all color directions, PSEs for the ‘separate’ and ‘combined’ conditions were significantly different: more luminance contrast relative to color contrast was required to achieve a PSE in the ‘combined’ compared to ‘separate’ condition, suggesting that in the combined condition the luminance variations were being masked by the color variations. Conclusion. Suprathreshold color variations mask suprathreshold brightness variations.
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