title: Colour detection thresholds in faces and colour patches.
abstract: Human facial skin colour reflects individuals' underlying health (Stephen et al 2011 Evolution & Human Behavior 32 216-227); and enhanced facial skin CIELab b* (yellowness), a* (redness), and L* (lightness) are perceived as healthy (also Stephen et al 2009a International Journal of Primatology 30 845-857). Here, we examine Malaysian Chinese participants' detection thresholds for CIELab L* (lightness), a* (redness), and b* (yellowness) colour changes in Asian, African, and Caucasian faces and skin coloured patches. Twelve face photos and three skin coloured patches were transformed to produce four pairs of images of each individual face and colour patch with different amounts of red, yellow, or lightness, from very subtle (deltaE = 1.2) to quite large differences (deltaE = 9.6). Participants were asked to decide which of sequentially displayed, paired same-face images or colour patches were lighter, redder, or yellower. Changes in facial redness, followed by changes in yellowness, were more easily discriminated than changes in luminance. However, visual sensitivity was not greater for redness and yellowness in nonface stimuli, suggesting red facial skin colour special salience. Participants were also significantly better at recognizing colour differences in own-race (Asian) and Caucasian faces than in African faces, suggesting the existence of cross-race effect in discriminating facial colours. Humans' colour vision may have been selected for skin colour signalling (Changizi et al 2006 Biology Letters 2 217-221), enabling individuals to perceive subtle changes in skin colour, reflecting health and emotional status.
authors.affiliation: School of Psychology, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan, Malaysia. khyx1tki@nottingham.edu.my
authors.forename: Kok Wei
authors.initials: KW
authors.lastname: Tan
authors.affiliation: School of Psychology, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan, Malaysia.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Stephen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D044466:Asian People / Q000523:psychology; D044383:Black People / Q000523:psychology; D003116:Color; D003118:Color Perception / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology*; D005145:Face; D005260:Female; D006801:Humans; D008296:Malaysia; D008297:Male; D044469:Racial Groups / Q000523:psychology*; D021641:Recognition, Psychology / Q000502:physiology*; D012880:Skin Pigmentation / Q000502:physiology*; D013334:Students / Q000523:psychology; D044465:White People / Q000523:psychology; D055815:Young Adult