Upper left: average of 22 Caucasian female faces
Upper right: average of 22 Caucasian male faces
Lower left: white pixels are where the female average is lighter than the male average
Lower right: white pixels are where the male average is lighter than the female average
To a large degree, we do not learn to recognize whether a human face is male or female (Bestelmeyer et al., 2008; Little et al., 2005). This mental task is mainly performed by a hardwired algorithm that uses certain visual cues, one of them being facial color (Frost, 1994). Men are more reddish-brown in complexion because their skin has more melanin and hemoglobin (Edwards & Duntley, 1939). Women are paler and show greater contrast between the color of their face and that of their lips and eyes (Russell, 2009). This algorithm is used not only for visual recognition but also for tasks apparently related to sexual attraction and social dominance (Feinman & Gill, 1978; Ioan et al., 2007).
Richard Russell has investigated the way we use facial color to identify male and female human faces. In one experiment, he morphed together 22 photos of Caucasian female faces and then 22 photos of Caucasian male faces. The participants were clean-shaven and did not wear make-up. As we can see from the above composites, the visually average face is noticeably lighter when it is female than when it is male. There is also greater contrast between facial color and lip/eye color on the female face than on the male one.
Russell (in press) argues that the human mind uses lip and eye color as a benchmark for visual processing of facial color:
If female skin is lighter than male skin, but female eyes and lips are not lighter than male eyes and lips, there should be greater luminance contrast surrounding female eyes and lips than male eyes and lips. This would be important, because the visual system is sensitive to contrast rather than to absolute luminance differences. Indeed, luminance contrast is the cue to which most neurons in the early visual cortex respond. Moreover, contrast internal to the face would be robust to changes in illumination. The black ink of this text under direct mid-day sun reflects more light than does the white page under dim indoor lighting, yet in both contexts the text appears black and the page appears white because the contrast between the two is constant. In the same way, a sex difference in contrast could be a particularly robust cue for sex classification. If there is a sex difference in contrast it would also mean that the femaleness of the face could be increased by lightening the skin or by darkening the eyes and lips—either change would increase the contrast. (Russell, in press)
He goes on to argue that this sex difference in facial color is reflected in the development of women’s cosmetics.
The received style of cosmetics involves darkening the eyes and lips while leaving the rest of the face largely unchanged. This is one of two patterns of cosmetic application that could increase facial contrast (the other being to significantly lighten the entire face, except for the eyes and lips). (Russell, in press)
This same pattern has appeared in a wide range of culture areas (ancient Egypt, Mesopotamia, South Asia, East Asia, Mesoamerica), in some cases independently of influence from other culture areas.
Bestelmeyer, P.E.G., B.C. Jones, L.M. DeBruine, A.C. Little, D.I. Perrett, A. Schneider, L.L.M. Welling, & C.A. Conway. (2008). Sex-contingent face aftereffects depend on perceptual category rather than structural encoding, Cognition, 107, 353-365.
Edwards, E.A., & Duntley, S.Q. (1939). The pigments and color of living human skin. American Journal of Anatomy, 65, 1-33.
Feinman, S. & G.W. Gill. (1978). Sex differences in physical attractiveness preferences, Journal of Social Psychology, 105, 43-52.
Frost, P. (1994). Preference for darker faces in photographs at different phases of the menstrual cycle: Preliminary assessment of evidence for a hormonal relationship, Perceptual and Motor Skills, 79, 507-514.
Ioan, S., Sandulache, M., Avramescu, S., Ilie, A., & Neacsu, A. (2007). Red is a distractor for men in competition. Evolution and Human Behavior, 28, 285-293.
Little, A.C., L.M. DeBruine, & B.C. Jones. (2005). Sex-contingent face aftereffects suggest distinct neural populations code male and female faces, Proceedings of the Royal Society of London, Series B, 272, 2283-2287.
Russell, R. (in press) Why cosmetics work. In Adams, R., Ambady, N., Nakayama, K., & Shimojo, S. (Eds.) The Science of Social Vision. New York: Oxford University Press
Russell, R.( 2009). A sex difference in facial contrast and its exaggeration by cosmetics, Perception, 38, 1211-1219
Russell, R. (2003). Sex, beauty, and the relative luminance of facial features, Perception, 32, 1093-1107.
Russell, R. & P. Sinha. (2007). Real-world face recognition: The importance of surface reflectance properties, Perception, 36, 1368-1374.
Russell, R., P. Sinha, I. Biederman, & M. Nederhouser. (2006). Is pigmentation important for face recognition? Evidence from contrast negation. Perception, 35, 749-759.