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International Journal of Cosmetic Science, 2005, 27,317–325

The biology of facial

B. Fink* and N. Neave *Department for Sociobiology/Anthropology, Institute for Zoology & Anthropology, University of Goettingen, Goettingen, Germany and Human Cognitive Neuroscience Unit, School of Psychology and Sport Sciences, Northumbria University, Newcastle upon Tyne, U.K.

Received 17 May 2005, Accepted 14 September 2005

Keywords: attractiveness, beauty, , , humans,

e´volue´ et jugent attrayants certains traits corporels Synopsis parce que ces traits sont ceux de personnes en It was once widely believed that standards of bonne sante´. Nous verrons dans cet article quel- beauty were arbitrarily variable. Recent research ques principes fondamentaux de la the´orie de la suggests, however, that people’s views of facial se´lection sexuelle qui s’appliquent a` la beaute´ attractiveness are remarkably consistent, regard- humaine et nous re´sumerons les principales de´cou- less of race, nationality or age. Facial characteris- vertes dans la de la beaute´ humaine. tics are known to influence human attractiveness and evolutionary psychologists suggest Introduction that these characteristics all pertain to health, leading to the conclusion that humans have Human assessments of beauty and human beauty evolved to view certain bodily features as attract- standards have attracted considerable attention in ive because the features were displayed by healthy recent years, not least by cosmetic companies, others. Here we review some of the fundamental plastic surgeons and scientists. A beautiful human principles of theory that apply to face provides the receiver with pleasurable feelings human beauty and summarize the major findings mediated by the brain’s dopaminergic reward sys- of human beauty perception. tem, especially when that face is staring directly at you [1]. In a seminal early study Dion et al. [2] showed that positive qualities are ascribed to Re´ sume´ attractive people and negative qualities to unat- Autrefois, l’ide´e que les standards de la beaute´ tractive people. More recently, Langlois et al. [3] varient de fac¸on arbitraire e´taient largement demonstrated that attractive children and adults re´pandue. Toutefois, de re´centes recherches sug- are judged more positively than unattractive chil- ge`rent que l’avis des gens sur l’attrait d’un visage dren and adults. A common notion however est remarquablement concordant inde´pendamment remains that ‘beauty is in the eye of the beholder’ de la race, de la nationalite´ ou de l’aˆge. Les and some feminist writers even dispute that beauty caracte´ristiques faciales sont connues pour influ- is an objective [4]. In contrast, - encer les jugements sur l’attrait humain et les ary psychologists criticize the idea that beauty psychologues de l’e´volution sugge`rent que ces reflects some arbitrary cultural , such caracte`ristiques rele`vent toutes de la sante´. Ceci scientists note that while some aspects of judge- conduit a` la conclusion que les humains ont ments may reflect cultural conventions, the geo- metric features of the human face that give rise to Correspondence: Bernhard Fink, Department for Socio- of beauty may reflect adapta- biology/Anthropology, Institute for Zoology & Anthro- pology, University of Goettingen, Berliner Strasse 28, tions. Human beauty standards may thus reflect D-37073 Goettingen, Germany. Tel.: +49 551 39 9344; culture-independent psychological adaptations fax: +49 551 39 7299; e-mail: bernhard.fi[email protected] reflecting mate choice characteristics (Fig. 1) [5].

ª 2005 Society of Cosmetic Scientists and the Socie´te´ Franc¸aise de Cosme´tologie 317 The biology of facial beauty B. Fink and N. Neave

Figure 1 Beauty standards may vary between the cultures, but dif- ferent ethnic groups seem to share a common attractiveness standard based upon biological rules. The are generated by means of digital image morphing technique and illustrate the universality of beauty without ethnic boundaries (Image courtesy: Karl Grammer, LBI for Urban Ethology).

Although beauty standards may vary between Sexual selection, health and beauty cultures and between times, several studies have shown that members of different ethnic groups Parasites and diseases have played an important share common attractiveness standards. For exam- role in human evolution, as they exert tremendous ple, Cunningham et al. [6] asked males from differ- selection pressures on their hosts by reducing their ent ethnic backgrounds to judge the attractiveness longevity and reproductive success. It has been of females from same and different racial groups. known for a long time that individuals differ in Mean ratings were highly positively correlated and their susceptibility to parasites because of genetic- such ratings did not appear to be influenced by ally determined host resistance, and sexual selec- exposure to Western media. In a meta-analytic tion for healthy partners would obviously provide review, Langlois et al. [3] demonstrated that choosy individuals with potentially important fit- within and between cultures, raters strongly agree ness benefits in terms of resistant offspring [8]. about who is and who is not attractive. The simi- Parasite-mediated sexual selection may benefit larity of such cross-cultural perceptions suggests choosy individuals by preventing them from that beauty standards are innate, a view streng- obtaining mates with contagious parasites that thened by studies demonstrating that human could spread both to themselves and their off- infants show strong preferences for attractive spring, obtaining mates that are efficient parents, faces. In one such study, Langlois et al. [7] utilized and obtaining mates that are genetically resistant a standard visual preference technique with to parasites [9]. infants aged 2–3 and 6–8 months old. In this Hosts may reliably avoid the debilitating effects method the infants were shown pairs of faces pre- of parasites by evolving efficient immune defences, viously rated for attractiveness – an attractive face and the immune system in humans is one of the was always paired with an unattractive face. Both energetically most costly, only equalled by that of groups of infants looked significantly longer at the the brain. Immune defence may play a role in host more attractive face of the two. Hence, the constit- sexual selection because secondary sexual charac- uents of beauty seem to be neither arbitrary nor ters may reliably reflect the immunocompetence of culture bound but may reflect underlying biologi- individuals [10]. Many secondary sexual charac- cal selection pressures that may have shaped these ters develop under the influence of testosterone standards. The high consensus of people’s judge- and sex hormones. However, hormones have ments of facial attractiveness is consistent with the antagonistic effects on the functioning of the theory of biologically based standards of beauty. immune system [10–12], and only individuals in

318 ª 2005 International Journal of Cosmetic Science, 27,317–325 The biology of facial beauty B. Fink and N. Neave prime condition may be able to develop the most to Morris [20], flawless skin is the most univer- extravagant secondary sexual characters without sally desired human feature and human males compromising their ability to raise efficient are expected to be most sexually attracted to immune defences. female skin that is free of lesions, eruptions, In the human face the basic proportions are warts, moulds, cysts, tumours, acne and hirsu- sexually dimorphic, as male traits develop under tism. The absence or presence of body hair is a the influence of testosterone and female traits sexually dimorphic characteristic, and relative develop under the influence of oestrogens. In the hairlessness and smooth skin in women may sig- case of the broad male chin as a feature of nal fertility because of its association with low attractiveness, the constraints seem to be known. androgen and high oestrogen. Females appreciate If females want dominant males, broad male men’s body hair developed under androgens, but chins may signal a tendency to dominate other males prefer its absence [18]. Skin infection may males. In eight different cultures, Keating et al. denote a disturbance of the production of andro- [13] have shown that males with broad chins gen and oestrogen and reduced reproductive are perceived as those who are more likely ability. Studies in dermatology have found a to dominate others than be dominated (see also relationship between dermatoses (i.e. physiologi- Ref. [14]). A broad chin could, however, also act cal and pathological changes that can occur in as a handicap [15] because testosterone produc- the skin, nails and hair shafts) and elevated lev- tion might be costly due to suppression of els of sex hormones [21, 22]. In numerous types immune function and thereby increase disease of dermatoses in women, an increase of the level susceptibility during puberty [10]. Immunocompe- of androgens seems to be responsible for these tence is highly relevant because steroid reproduc- symptoms. For example, the polycystic ovary tive hormones may negatively impact immune syndrome results in an overproduction of andro- [10]. Extreme male features, which are triggered gens, which is clinically manifested as dermatos- by testosterone, thus advertise reliably that their es in women [23]. bearer is sufficiently parasite resistant to produce Empirical evidence shows that women’s facial them. skin texture affects males’ judgements of their The causal relationship between testosterone facial attractiveness, and homogeneous (smooth) levels and these behavioural attributes is still con- skin is most attractive (Fig. 2) [24]. Males evalu- troversial (see review in Ref. [16]). If such rela- ate females’ skin texture in addition to the char- tionships are valid, then the aesthetic preference of acteristics of age and facial shape in judging human females may be an adaptive compromise facial beauty. Fink et al. [24] also found that between the positive attributes associated with colour parameters that indicate a light skin as higher than average testosterone (health cues) and well as blue and green components in a face the negative attributes associated with more correlated negatively with attractiveness. In con- extreme masculinization. trast, saturation showed a significant positive The signalling of many female physical correlation with attractiveness. The red compo- characteristics is linked to age and reproductive nent showed a positive but statistically insignifi- condition, both of which correspond to a woman’s cant correlation with attractiveness. These ratio of oestrogen to testosterone. Attractive fea- authors interpreted this finding in terms of the tures (e.g. prominent cheekbones) correspond to suggestion that a slightly reddish skin (indicating high ratios and signal fertility, but oestrogen in good blood circulation) is considered attractive women could be as handicapping as testosterone and healthy. In contrast to previous studies is in men. Thus, markers of high oestrogen may [25], Fink et al. [24] did not find that men pre- reliably signal that a female’s immune system is of fer women with a paler skin. The preference for such high quality that it can deal with the toxic dark skin may be explicable in terms of a prefer- effects of high oestrogen. ence for suntanned skin. The condition of the skin surface may thus pro- vide an indication of the quality of the immune Skin condition and beauty system of the respective individual. A reduced Skin condition is supposed to reliably signal immune defence provides the possibility of a more aspects of female mate value [17–19]. According aggressive attack by micro- and macroparasites

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Figure 2 Analysis of skin texture qualities by means of spatial grey level dependency matrices. Within the rectangle over the cheeks and nose, an enhancement filter increa- ses contrast in the face for the sub- sequent calculation of homogeneity and contrast features (Image court- esy: Paul Matts, Procter & Gamble).

[26], which may be indicated in skin surface tex- metrical men [29, 30]. Symmetrical people of both tures. Therefore, biologists argue that the use of sexes are reported to have greater emotional and makeup in modern societies may be functional psychological health, and symmetrical men were and deceptive. also found to have greater physiological health, than their asymmetrical counterparts [31, 32]. A number of studies have shown a relationship Facial between symmetry and attractiveness leading to Besides secondary sexual characteristics and the conclusion that preferences for symmetric faces aspects of skin condition, evolutionary psychology may have some adaptive value. However, despite has focused on the perception of the correlation between symmetry and attractive- and averageness, and suggested that this may ness, it appears that human females may not use underpin biologically significant assessments of or even perceive fluctuating asymmetries when mate value. – non-direc- judging the attractiveness of male faces [33]. tional deviations from perfect symmetry in These results suggest that attractive features other morphological characters – as measure of develop- than symmetry can be used to assess physical con- mental stability is thought to reflect an ability to dition. Symmetry may simply covary with these resist the harmful effects of mutations, parasites other features rather than acting as a primary cue and/or toxins during development (Fig. 3) [27]. to attractiveness. It may be the case that the Across species, symmetrical males have signifi- human preference for facial symmetry is not the cantly greater mating success [28], and symmetri- result of evolved psychological adaptations, but cal men have been shown to be more desirable rather is a by-product of the perceptual system’s and have more sexual opportunities than asym- design.

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Figure 3 These faces (a ¼ Japan- ese, b ¼ Caucasian) are both per- fectly symmetrical as a result of digital blending of a face with its mirror image. Symmetry as a meas- ure of developmental stability is known to be associated with beauty perception. Image (a) depicts some of the distances, which are used for measuring right–left deviations from perfect bilateral symmetry.

possess a shorter, narrower lower jaw, fuller lips, Facial averageness and larger eyes than an average face [37, 38]. The study of facial symmetry effects on attractive- Because pubertal bone growth (brow ridges and ness is closely related to another possible cue to lower jaw) is stimulated by androgens [39] and lip attractiveness: facial averageness (Fig. 4). Experi- fullness parallels oestrogen-dependent fat deposits ments studying the effect of facial symmetry on elsewhere on the female body [40], Johnston and perception suggested that preference for average Franklin [37] have hypothesized that an attractive trait values in some facial features could have female face may be displaying hormone markers evolved because in heritable traits the average (high oestrogen/low androgen) that serve as reli- denotes genetic heterozygosity [11]. Heterozygosity able indicators of fecundity. could signal an outbreed mate or provide genetic Some of the discrepancy in findings among male diversity in defence against parasites. Studies indi- attractiveness studies may be a consequence of dif- cate that average faces are attractive but can be ferences in the participant populations. One poten- improved by the addition of specific non-average tial source of variance is the hormonal status of features. However, Halberstadt and Rhodes [34] female participants. Penton-Voak et al. [41] have found a strong relationship between averageness shown that females’ preferences for male faces and attractiveness also for stimuli like dogs and changed as a function of the viewer’s menstrual wristwatches. It may be that humans have a gen- phase at the time of testing. Females tested during eral attraction to prototypical exemplars, and that the 9 days prior to ovulation preferred a less femi- their attraction to average faces is a reflection of nized male face than females tested outside of this this more general attraction. The contribution window. The authors interpret their findings as of averageness to attractiveness is still a matter of evidence for a conditional mate choice strategy debate [35]. Exactly what features contribute to whereby females in the high conception risk group the averageness effect remains unclear. Most stud- are exhibiting a preference for male facial cues ies find that there are some faces in the tested that signal adaptive heritable genetic characteris- samples that are considered more attractive than tics, such as immunocompetence. Further, relat- average faces [36]. The conclusion of studies ively feminine faces possibly indicate prosociality focusing on the attractiveness of averaged faces is whereas more masculine faces possibly signal still questionable. It could be that these faces show reproductive potential in terms of heritable bene- non-average features, which are developed under fits. Johnston et al. [42] also examined the facial the influence of sex hormones. There is now sub- preferences of female volunteers at two different stantial evidence indicating that attractive female phases of their menstrual cycle. In agreement with faces are not average, but differ from the average prior studies [41], their results suggest that in a systematic manner. More specifically, they women prefer more masculinized male faces

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Figure 4 Computer-generated pro- totypical faces (composites) are known to be rated higher attractive than the single faces, which were used for generating them. Here this is illustrated with 15 single faces (left), and the resulting composite face (right) (Image courtesy: Paul Matts, Procter & Gamble).

Figure 5 Menstrual cycle alters face preference. While women tend to prefer masculine male faces (a) around ovulation, they have a pref- erence for feminized male faces (b) at the other days of their cycle. This probably indicates an adaptive com- promise between interest in males that seem to guarantee reproductive success and males perceived as ‘good fathers’ (Image courtesy: Vic- tor Johnston, New Mexico State Uni- versity). around times of ovulation. That is, the attractive facial metric approach to the study of beauty and male face possesses more extreme testosterone found that female facial attractiveness is greater markers, such as a longer, broader lower jaw, and when the face has certain features, large eyes and more pronounced brow ridges and cheekbones thin eyebrows being of prime importance. The than the average male face (Fig. 5). This finding importance of the eyes in judgements of attractive- suggests that women consider such testosterone ness is known even in children. Geldart et al. [46] markers, whether this is because such characters studied the influence of eye size on adults’ ratings act as an index of good health and that important of facial attractiveness and 5-month-olds’ looking health considerations may underlie their aesthetic times. When using realistic photographs, babies preference remains to be determined (see Ref. [43] looked significantly longer at the faces with larger for review). However, pronounced testosterone eyes, suggesting that a preference for larger eyes facial markers were considered to be associated has emerged even at the age of 5 years. Other with dominance, unfriendliness, and a host of neg- studies suggested that luminance effects of facial ative traits (threatening, volatile, controlling, features might account for variation in attractive- manipulative, coercive, and selfish). ness ratings. This effect is known and enhanced by the application of cosmetics, i.e. in order to make the female face more attractive the eyes are The beauty of eyes and lips darkened with the use of make-up. Russell [47] It has been shown that the eyebrows receive the confirmed this influence upon attractiveness judge- highest rank in the order of magnitude of gender ments by suggesting that increasing or decreasing carried by parts of the face [44]. More the luminance difference will make a face more recently Baudouin and Tiberghien [45] applied a feminine or masculine, respectively, and hence,

322 ª 2005 International Journal of Cosmetic Science, 27,317–325 The biology of facial beauty B. Fink and N. Neave more or less attractive. Moreover, these effects it seems likely that humans have evolved mecha- seem to be opposite for men and women. Female nisms for detecting and assessing honest cues of faces were found to be more attractive when this mate value. In this view, luminance difference was increased whereas male is based upon the detection of reproductive poten- faces were rated higher on attractiveness when it tial in males and females. Natural and sexual was decreased. selection are thought to have operated in a way In contrast to study of the attractiveness of the that men and women who were best suited for eyes and eye , attractiveness research has paid tasks such as hunting or food gathering activities little attention to the lips, although they are appar- were most attractive to potential mates. Today, ently a central feature in the lower face. When the face, as a permanently visible source of infor- they are full and well defined, they impart a sense mation still seems to signal reproductive potential of youth, health and attractiveness. Thin, flat lips, and beauty, and the cosmetics industry taps into on the other hand, imply fragility and senility [48]. this by producing a wide range of products adver- Lipsticks even determine the first impression of per- tised to enhance facial characteristics in both sonality. McKeachie [49] reported that young male men and women, specifically to make us look students rated women as more frivolous, less talk- younger, healthier and more attractive. Facial fea- ative, more anxious, less conscientious, and more tures enhanced by such products are still those interested in the opposite sex when wearing make- our ancestors have been looking at. Hence, in up than when not. This has only recently been rep- this view, beauty is not only ‘skin deep’ but licated by Richetin et al. [50]. These authors used rather lies in the adapted preferences of the the Implicit Association Test to study attributions beholder. towards women wearing or not-wearing make-up and found that those wearing make-up were regar- References ded in a more positive way and assumed to have higher professional status. 1. Kampe, K.K., Frith, C.D., Dolan, R.J. and Frith, U. Such effects have been well known by make-up Reward value of attractiveness and gaze. artists and cosmetic surgeons for years. But where 413, 589 (2001). does the obsession with having beautiful lips come 2. Dion, K.K., Bergscheid, E. and Walster, E. What is from? Evolutionary psychologists consider also the beautiful is good. J. Pers. Soc. Psychol. 24, 285–290 (1972). shape and colour of the lips as an indicator of 3. Langlois, J.H., Kalakanis, L., Rubenstein, A.J. et al. youth and fertility. Full lips in women are devel- Maxims or myths of beauty? A meta-analytic and oped under the influence of oestrogens, and sev- theoretical review. Psychol. Bull. 126, 390–423 eral other features of the face and body that (2000). indicate fertility develop under the influence of 4. Wolf, N. The beauty myth. Morrow, New York sex-steroids. There is however another interpret- (1991). ation for the fact that women themselves apply 5. Thornhill, R. and Grammer, K. The body and face of exclamation points to their lips. The most often women: one ornament that signals quality? Evol. used colour for lipsticks is probably red, and this is Hum. Behav. 20, 105–120 (1999). also the colour of blushes and flushes. It signals 6. Cunningham, M.R., Roberts, A.R., Barbee, A.P., both good blood circulation and presumably also Druen, P.B. and Wu, C-H. ‘Their ideas of beauty are, on the whole, the same as ours’: consistency and emotional arousal or perhaps even sexual excite- variability in the cross-cultural perception of female ment. By applying lipstick women therefore simply physical attributes. J. Pers. Soc. Psychol. 68, 261– enhance the amount of natural (red) colour by 279 (1995). exaggerating these facial characteristics men are 7. Langlois, J.H., Roggman, L.A., Casey, R.J. et al. attracted to. Infant preferences for attractive faces: rudiments of a stereotype? Dev. Psychol. 23, 363–369 (1987). 8. Hamilton, W.D. and Zuk, M. Heritable true fitness Conclusion and bright birds: a role for parasites? Science 218, Evolutionary psychologists widely agree that there 384–387 (1982). are biological reasons for certain face preferences 9. Møller, A.P., Christe, P. and Lux, E. Parasite-medi- in potential partners. Given that evolutionary pro- ated sexual selection: effects of parasites and host immune function. Q. Rev. Biol. 74, 3–20 (1999). cesses have shaped our psychological adaptations,

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