Abstract
Asymmetries in blue-yellow color perception, in which blues appear less saturated than yellows of equivalent chromatic contrast, have been shown to affect a variety of color percepts including the appearance of #thedress (Winkler et al, 2015). This asymmetry may reflect greater ambiguity about the source of bluish tints compared to other hues, e.g., whether the blue is due to the lighting or the surface. When the blue is inverted to yellow, this ambiguity may be removed, and agreement about the inverted dress color is much higher. We tested for neural correlates of this perceptual asymmetry using a paradigm for measuring asymmetries in visual discrimination with high-density electroencephalography (EEG) and frequency tagging (Retter & Rossion, 2016). Throughout four 50-sec sequences, the original dress image was presented in alternation with the color-inverted image at a rate of six images per second (6 Hz), with measurements collected for 14 observers. Given that the color-inverted image is consistently perceived to have yellow stripes, we hypothesized that an asymmetry between the two images would be present in the EEG recording at the alternation rate (3 Hz). Settings were also made for a second pair of dress images formed by rotating the original colors by +/-90 deg to create reddish-greenish versions, for which a less-pronounced perceptual asymmetry predicts a weaker 3 Hz response. These hypotheses were supported, with larger blue-yellow than red-green responses at 3 Hz and its specific harmonics (e.g., 9 Hz) in the frequency-domain of the EEG over occipital channels. In contrast, the response at the image-presentation rate of 6 Hz and its harmonics did not differ across these two conditions. Our results suggest that the blue-yellow asymmetry, a potentially higher-level aspect of color appearance unrelated to chromatic sensitivity, is nevertheless evident in electrophysiological recordings of the cortical responses to color.
Meeting abstract presented at VSS 2017