Thursday, 1 October 2009

Facial color and sex recognition

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.

References

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.

16 comments:

ItsTheWooo said...

Today, there is a trend in womens cosmetics to darken the face but leave the eyes and lips pale. This is known as bronzing, it is acheived via tanning and bronzing powder. Bronze complexions look best with natural eye and lip color (gold, nude, pink etc) because dark eye and lip color on brown skin looks excessive dirty and skanky (e.g. christina agueilera when she was "dirrty")

Even though a relative paleness of skin is feminine, it should be recognized that in industrialized tanning is a sign of not being a worker and of wealth; this has driven many women to darken their complexions and to minimize the contrast between lips eyes and face so as to accentuate the "natural" tan.

It could be, also, that paleness traditionally signified wealth and this is why traditionally women try to accentuate paleness. Sort of how it used to be that plumpness was a sign of wealth whereas now it is a sign of ignorance and poverty (as ignorant impovershed people lack discipline or knowledge or access to healthful food that protects against the development of obesity).
As a result women are gravitating toward a level of thinness that is totally pointless, maladaptive and even frankly unattractive (indicating infertility and sickness) simply because it is attractive by association with teen youth and wealth.



It should also be mentioned that a major reason pale faces are considered feminine is because testosterone makes the face more angular, which will increase shadows and shade on the face, giving it a darker appearance. The infantile feminine face is pale in comparison by a lack of prominence of structures other than lips and eyes. Undoubtedly sex-steroid changes in hgb synthesis and pigment are also responsible.

Tod said...

Assuming that white skin originally appeared in Europeans who had very dark brown or "black" eyes would the contrast between the colour of the face and eyes not be reduced by the lighter novel eye colours?

Women with light coloured eyes may have needed an especially pale skin to maintain the contrast and look as feminine as the dark eyed women.

The extremes of white skin seen today in Europeans might have only become necessary when novel eye (and possibly hair ) colours appeared



Alternatively if skin became fully white before novel colours appeared dark eyed females may have simply got a bit of an advantage by having the most extreme eye - skin contrast.

sestamibi said...

Why do you need to show two comparisons? If in the first the white areas are those where the female composite is lighter, then by definition aren't the black areas those where the male composite is lighter?

Anonymous said...

Peter, it's been my contention that in the faces of little boys who turn out to be gay, one can spot feminine characteristics in the face just from their pictures so when I read this post, I was reminded of my belief that I possess a certain degree of gaydar.

So..take a look at the face of this young boy in the link, if you wouldn't mind. I mean, even w/out ever having seen the pic in the context of the story, I know I would have said this kid is (or is going to be) gay.

When I first read your post on the subject of male/female facial characteristics, I went back looking for this pic and finally found it.

This kid looks very feminine to me, but until your post, I didn't know why I felt that way, why I often feel that way, just that I did. Now, I'd guess I feel that way about him (and others) because there's a strong contrast between his skin color and lip/eye color.

I am wondering, therefore, if it might be true that in a fair % of kids, there are facial differences between young boys who turn out to be gay and those who turn out to be straight. Is is possible this could be a predictor?

What this means, I've no idea other than I do believe I have some level of gaydar and that gay kids have facial characteristics that are feminine, even at a very early age.

Anonymous said...

Sorry, forgot to give the link!

http://www.abcnews.go.com/2020/Story?id=4529843&page=1

Peter Frost said...

Its TheWooo,

I suspect that sex recognition of human faces involves two separate mental algorithms:

a) evaluate the relative lightness of facial skin;
b) evaluate the relative contrast between facial color and eye/lip color.

In women's fashion, there has been a marked change in (a) but not in (b). Use of lipstick and eyeliner has actually increased during the period (post mid-1920s) of female suntanning. So fashion trends don't seem to contradict the second algorithm.

The big question is why the suntanned look entered women's fashion. The immediate cause was the medical profession, which saw suntanning as a means to fight tuberculosis and rickets - the two main intractable illnesses of the Western world in the early 20th century. This doesn't really explain, at least not to my satisfaction, why this health fad became a fashion and why it has persisted at a time when it is no longer supported by the medical community.

You mention social class as a factor. Actually, if we look at the people who pioneered the tanned look in the 1920s, they were mainly young, urban, educated, and single (like initiators of fashion trends today). There were some rich people among them, but most were not. The wealthy and established tended to be followers not leaders.

The entry of the tanned look into women's fashion coincided with a shift toward androgyny: bobbed hair, large shoulders, small bust and a generally 'boyish' appearance, i.e., the 'flapper' look (which in French is tellingly called 'la garconne').

All of this raises more questions than answers. We need more information about the behavioral/emotional outputs of this mental algorithm.

Tod,

The same question came to me. I suspect that the shift toward a lighter skin color among ancestral Europeans increased the contrast between facial color and eye/lip color and thus relaxed sexual selection of women with dark eyes and dark hair. This, in turn, may have allowed the 'rare color effect' to become a significant force in sexual selection.

Alternately, the 'rare color effect' may have always been a weak selection pressure that manifests itself only under conditions of intense sexual selection.

Sestamibi,

I think it's important to show that some pixels are actually lighter in the lip and eye areas of the male face. An intelligent observer could deduce that from the first picture, but not everyone would make that deduction.

Anon,

I don't believe that there's a 'gay gene'. Male homosexuality seems to be due to a weak genetic predisposition that interacts with a much stronger environmental factor that intervenes during pregrancy or early infancy. This genetic predisposition, in itself, would not make a man gay. It probably would make him more feminine in terms of caring for children (Ed Miller's theory).

Something else seems to transform this predisposition into full-blown male homosexuality, perhaps a pathogen (Greg Cochran's theory) or an environmental estrogen (my theory). I agree with Cochran's contention that a true 'gay gene' would quickly select itself out of the gene pool.

P.S. The kid in the picture looks normal to me.

Anonymous said...

Peter,

Actually, I am a believer that Greg Cochran's hypothesis is the best explanation of gayness, but I had to point out that I am so often right being able to tell a gay kid from a facial pic, it's weird. I've no explanation for it, but that kid's face is gay all over no matter how crazy that notion might seem to others. Go figure.

ItsTheWooo said...

Peter – It really doesn’t matter if makeup use has increased along with the trend in tanning. All this tells me is that women are using more makeup and they are getting more tans, which is an obvious deduction that has more to do with consumerism and prosperity… it does not mean that tanning is leading women to use makeup to accentuate their paleness (that is totally illogical behavior… why tan in the first place if you are just going to accentuate your paleness via lipstick and eyeliner?). I would also point out that many lipsticks are pale, and in recent years lip gloss (which is sheer, but glossy, enhances the size/fullness of lips) has become preferred to lipstick especially for younger women who do the tanning thing. And, like I said, when women get tans and also wear a lot of dark eye make up and lipstick they just end up looking skanky and unnatural. This look has been parodied in popular culture. When my skin is more tanned, I get a lot of compliments, so I would challenge your perception that men find tanned skin masculine in general. Just because relative lightness of face is one sex indicator doesn’t mean it is a very important one.

I agree that skin lightness (and contrast between eyes/lips/face) is a major indicator of sex and femininity… but you are ignoring the equally important and powerful effect of class and resulting fashions. The tanned look says you have money and leisure time. We have a conditioned association between tans and wealthy beautiful people, so much to the point that if you have a tan people automatically find you more beautiful too.
Today, the pale look says you spend a lot of time indoors, nothing more. This can be either for one of two reasons: you are either mentally intense (“gothic”, “punk rock”, “artistic”, “emo”, “depressive”, etc) or it says you are an underclassling (work in an office all day and are quite dull). It simply is not true that we orniment ourselves to maximize biological indicators of femininity, we also orniment ourselves to accentuate our identities and egos and group affiliations (someone who makes the face excessively pale , dying the hair dark, male or female, is trying to point out what a creative artistic and alternative person they are).
For example, skinniness isn’t very feminine, but it doesn’t change the fact that it is fashionable and almost all women would like to be skinny if it were possible to choose to be so without any effort.

When I said “wealthy”, I didn’t mean extremely wealthy… I meant socially important which is synonymous with minimum/moderate amounts of financial resource. Extremely wealthy people are generally not cool, I agree, but it is true a minimum amount of wealth is held by the initiators of social fashion trends. They aren’t desperately poor and they aren’t extremely wealthy. They tend to be comfortable and they have time/resources to pursue social interaction and creativity because of that. Wealth is just one aspect of coolness, not the most important part by any means. Youth is just as important, and so is creativity and social ability… lots of ingredients in this mix.

I really don’t think the tanned look is a statement about androgyny. Again I am going to say it is a statement about class. Mentally when we imagine a tanned middle/upper class person we imagine them on their way to and from the gym and general leisure activities… they aren’t sitting at their desks all day.

I would also mention that flappers are generally pale with dark lips, so if the trend of tanning relates to the trend of boyishness as a female ideal, the flappers themselves don’t rock the look.

ItsTheWooo said...

I think the only fair conclusion is this: while skin color is a good indication of sex and gender, it isn’t hugely important. So, it is possible for antithetical behaviors to exist which appeal to a stronger ego drive (e.g. the trend of tanning which makes us feel wealthy and famous, makes us look like we are out and about in the sun instead of working indoors all day like we do in reality).

I would also argue that skin color isn’t as important as the overall quality of skin. Estrogen makes the skin plump, soft, clear (no blemishes)… there is a specific look to the skin of healthy young women, and this quality is most important. Color is just one part, and it isn’t a major one, because ethnicity affects skin color too (and I don’t think men would consider attractive women who are a bit darker like Adrianna lima to be less feminine or attractive than some pale as a ghost overweight unhealthy woman at walmart, lol).

ItsTheWooo said...

Re: gay gene...

It is shown that men who are homosexual have (1) a higher number of older brothers and (2) a 2d:4d ratio that suggests very high prenatal testosterone. It is shown that women who have large numbers of boys will have higher testosterone levels during pregnancy with each successive boy. The so called gay gene probably doesn't program for male homosexuality in general as much as it does program female relatives to have lots of boys with higher testosterone during development. This is an advantage, as male offspring can have more children and testosterone before birth can help males be successful... at least until the last boys are exposed to so much testosterone that it converts to estrogen excessively and programs sex behaviors in line with the opposite sex (homosexuality and/or femininity)

Environmental pollutants / estrogens may also be a factor.

But, it is generally true that male homosexuals show the signs of having been exposed to very high testosterone (not too little), e.g. a 4th finger that is very long compared to the 2nd... and they also have older brothers more commonly.


There are no known genetic links to female homosexuality (other than conditions which can cause frank ambiguous gender/sexuality, such as CAH). But, the 2d:4d ratio of female homosexuals is generally more masculine (especially if they self identify as such) so it seems that female homosexuality is also a condition of high prenatal testosterone/androgens, just like male homosexuality.

Anonymous said...

To Its the Woo,

My apologies, Peter, for going OT:

The so-called "older brother effect" hypothesis of gayness has been debunked by recent research-- one major study in 1996 by Bogaert and the most recent (2008)by Andrew Francis of Emory University.

ItsTheWooo said...

I did a quick google on this; I am not familiar with Francis but his introduction to his research makes him sound as if he has an agenda. I.E. he does state that having multiple older brothers slightly raises the risk of male homosexuality, that having a single older brother is neutral, and that having older sisters is "protective". He didn't exactly debunk it but his own findings do seem to support the idea that more brothers before you = more likelihood of developing homosexuality. At BEST he is conceding the effect isn't that strong.

And, this doesn't address the 2d:4d findings, which really is the more relevant aspect of the hypothesis (that high testosterone, as opposed to low, is implicated in both male and female homosexuality although perhaps for different reasons, i.e. in male homosexuality it may be that very high testosterone is converting to estrogens programing a proclivity to female sexual identity and behavior whereas in female fetuses is it simply masculinizing the brain).

Anonymous said...

-from the Francis study (which had a large sample)

"For men, I find that having one older brother does not raise the likelihood of homosexuality. Although having multiple older brothers has a positive coefficient, it is not significant. Moreover, having any older sisters lowers the likelihood of homosexual or bisexual identity. For women, I find that having an older brother or having any sisters decreases the likelihood of homosexuality."
**************
The "positive coefficient" of older brothers was "not significant."

BTW, hormonal hypotheses have also run into plenty of trouble too.

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Anonymous said...

Wait, so this is saying, since I have dark eyes(black) and dark hair(black), but pale light skin.....I am more feminine?? So this is why women find me unattractive...??

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