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Rosa Lafer-Sousa, Bevil Conway; #thedress: A Tool for Understanding How Color Vision Works. Journal of Vision 2017;17(10):136. doi: https://doi.org/10.1167/17.10.136.
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© ARVO (1962-2015); The Authors (2016-present)
The "dress" photograph provides an opportunity to investigate how the brain resolves stimulus ambiguity to achieve color. We analyzed responses from a large number of naïve and non-naïve subjects, collected in lab and online. First, contrary to initial scientific reports suggesting a wide range of dress percepts, using K-means clustering to analyze color-matching responses we find the dress was viewed categorically (white/gold and blue/black) among observers who had seen the photograph before and naïve subjects (color-matching responses predicted subjects' categorical labels, binomial regression). As well, 48% of observers self-reported experiences of perceptual switching (W/G switched less often). These results show that #thedress is analogous to bi-stable shape images. Second, we quantitatively compared color-matching responses obtained online and in laboratory, and performed a power analysis to determine the number of subjects required to obtain results representative of the general population. We conclude that initial scientific studies were underpowered. Third, observers descriptions of the lighting conditions were predictive of the colors seen (binomial regression); W/G observers typically inferred a cool illuminant, whereas B/K observers inferred a warm illuminant. Fourth, subjective reports of where in the image subjects looked revealed systematic differences between B/K and W/G observers. Fifth, we show here that when the dress is cropped from the rest of the photograph, and digitally placed on a female model, a color tint applied to the model's skin that reflects the illuminant was sufficient for observers to disambiguate the illuminant color and achieve a predictable perception of the dress' colors. Finally, presenting versions of the photograph with unambiguous lighting cues influenced how subjects reported the dress' colors in subsequent viewings of the original photograph. Together the results document a powerful example of a bi-stable color image, and illustrate how multiple perceptual and cognitive cues are used by the brain to resolve color.
Meeting abstract presented at VSS 2017
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