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Sophie Wuerger, Tushar Chauhan, Ali Sohaib, Julian Yates, Kaida Xaio; The sensitivity of the human visual system to subtle skin tone changes . Journal of Vision 2016;16(12):643. doi: 10.1167/16.12.643.
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© ARVO (1962-2015); The Authors (2016-present)
Skin reflectance can be modulated along two dimensions by haemoglobin: varying the haemoglobin oxygen saturation or the haemoglobin skin concentration. Changes in haemoglobin oxygen saturation leads to specific changes in the reflectance spectra (a 'W' spectral signature; Changizi et al. , 2006, Biol Lett. 2, 217) and is associated with a colour shift towards red. Changizi et al. argue that trichromatic vision may be optimised for discerning small colour changes associated with haemoglobin oxygenation. We tested this hypothesis in two ways. We first analysed a large data set of skin spectra to test whether this spectral signature of oxygenated haemoglobin is present, and whether it depends on body location. Another prediction is that human observers should be particularly sensitive to small colour changes consistent with the oxygen saturation of haemoglobin. To test his hypothesis, we conducted a psychophysical discrimination experiment with calibrated skin images to obtain thresholds in 8 different isoluminant colour directions including the direction associated with haemoglobin oxygenation. Analysis of skin spectra obtained from 188 participants show that the 'W' feature is indeed present in the skin spectra, with troughs at about 540 and 575nm and that the 'W' feature is most prominent in the cheek area compared to the neck area and to the forehead. These findings are consistent with the idea that the human colour system is optimised to detect oxygenation changes. In contrast, our preliminary psychophysical experiments do not show a greater sensitivity in the direction association with oxygen saturation of haemoglobin. Based on our preliminary analysis, we find partial support for the hypothesis that our visual system is optimised to discern small changes in facial redness which are diagnostic of mood and health states.
Meeting abstract presented at VSS 2016
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