Presidents’ Award Putting beauty back in the eye of the beholder

ANTHONY LITTLE and DAVID PERRETT (winner of the 2000 Presidents’ Award for Distinguished Contributions to Psychological Knowledge) discuss evolution and individual differences in face preference.

UR magazines and television This problem with considering beauty evolutionary theory, which posits that the screens are filled with images as only in the eye of the beholder is nicely attractiveness of individuals is directly O of ‘attractive’ people, and it is illustrated in Figure 1. Here, the two faces linked to their value as mates. High-value obvious that both women and men are are both symmetric and have perfectly mates are those who can best enhance the highly concerned with good looks in smooth skin, yet the composite on the right reproductive success of the individual who a partner. But exactly what is it that makes made from the faces of 50 models is chooses them. Individuals who were a face beautiful? What makes people seek systematically different from the composite attentive to cues to high mate-value, and out and desire to mate with the owners of student face in both shape and coloration. based mate-choice decisions on these cues, beautiful faces? Most people will agree it is more attractive. left behind more offspring (and so more It is difficult to verbalise what Some people are beautiful and some people genes for attending to attractive cues) than differentiates average from good-looking are not, and most people agree on who is those who failed to attend to these cues. individuals, and in modern times there is and who is not beautiful. Such evolutionary reasoning can also be a pervasive view that attractiveness simply Agreement between individuals is in applied to humans. In essence, the cannot be defined. Common phrases such fact one of the best-documented and most evolutionary view suggests that when as ‘beauty is in the eye of the beholder’ and robust findings in facial attractiveness making attractiveness decisions we are all, ‘beauty is only skin deep’ are testaments to research since the 1970s. Across many albeit unconsciously, asking the question our belief that attractiveness is ephemeral. studies it has been found that there is ‘What can the owners of beautiful faces do For example, the philosopher David Hume a high degree of agreement from for us in order that our genes survive to is often quoted for making the argument individuals within a particular culture, and subsequent generations?’ that beauty ‘is no quality in things high agreement between individuals from In many studies this evolutionary view themselves: it exists merely in the mind different cultures (see Langlois et al., 2000, of attractiveness has been powerful in which contemplates them; and each mind for a meta-analytic review). If different predicting the specific characteristics of contemplates a different beauty’ (Hume, people can agree on which faces are attractive faces (see Thornhill & 1757, p.208Ð209). attractive and which faces are not attractive Gangestad, 1999, for a review). A central But something in this politically when judging faces of varying ethnic tenet of the evolutionary view is that correct view of beauty just does not ring background, then this suggests that people individuals should agree on the true. Admittedly the latest big movie star everywhere are all using the same, or at characteristics that make up attractiveness is not everyone’s favourite pin-up; but it is least similar, criteria in their judgements. (e.g. Langlois et al., 2000). For example, undeniable that on average Hollywood males who preferred women past stars are generally more attractive than Evolution and attractiveness reproductive age would not have left their the people we meet in the street. You may Physical appearance is important to genes in the next generation and so we disagree over your best friend’s choice of humans and there appear to be certain partner but there are countless individuals features that are found attractive across FIGURE 1 that you and your friend could agree were individuals and cultures. The same holds more or less attractive than the particular true across the animal kingdom: most partner. non-human species rely on external factors, such as the sizes, shape and colour of adornments (e.g. feathers, fur, and fins) to attract mates. Research on animals has WEBLINK focused on individual traits that are For information on experiments and to attractive across individuals (and even participate in ongoing research: species) such as symmetry (e.g. M¿ller www.perceptionlab.com & Thornhill, 1998). Such experiments are driven by

28

The Psychologist Vol 15 No 1 January 2002 Presidents’ Award

might expect a universal preference for FIGURE 2 assortative mating occurs when individuals youth in males. form pairs in which the individuals Proposed universal preferences are involved are more similar to each other consistent with the cross-cultural than would be expected by chance (Burley, agreement on attractiveness. For example, 1983). In humans, mating with similar youth, which is associated with fertility and individuals to oneself may have genetic the potential for offspring production in benefits. For example, Thiessen and Gregg women, has been found to be attractive in (1980) have proposed that mating with faces across individuals and cultures (Buss, similar-looking individuals increases the 1989). We will now look in more detail at chances that those individuals have genes another example of a universal in common with you, and that mating with characteristic of beauty and its proposed such individuals can be advantageous to evolutionary root. your genes. Of course the advantages of mating with similar individuals has its Facial symmetry limits. Mating with your close family Research on symmetry has been may be a range of mating strategies members is referred to as inbreeding, conducted on many animal species and that can be employed based on both which reduces genetic diversity and provides a good example of a characteristic environmental cues and individual physical increases the chances of harmful recessive of human faces that is proposed to be attributes. In humans, whilst individuals genes being expressed in offspring. The attractive across observers. Symmetry may share certain basic criteria for finding best strategy might be to avoid mating with refers to the extent that the left half of an faces attractive, many factors may close relatives but to mate with someone organism is the same as the right. It is influence the specific types of face they genetically more similar to you than a significant characteristic, as it can be seen find attractive. average. Bateson (1982) called this notion as a measure of the ability of an organism optimal outbreeding and demonstrated its to cope with environmental stress (e.g. food Look-alikes occurrence in Japanese quail. Birds of both scarcity): the optimal developmental It is a widespread belief that partners look sexes were attracted to first cousins over outcome for most characteristics is alike (e.g. the 1930 portrait by Grant Wood siblings and unrelated individuals. symmetry. Only high-quality individuals called American Gothic, below). Positive Early research on assortative mating in can maintain symmetric development under environmental and genetic stress; therefore symmetry can serve as an indicator of the quality of an individual as well as the quality of their genes (see M¿ller & Thornhill, 1998). For example, individuals with genes coding for strong immune function will be more resistant to infection, allowing their bodies to grow more symmetrically than individuals with lower immune capacity, who will be ‘stressed’ more by exposure to the same infection. When manipulating symmetry with computer graphics, symmetric faces are found to be preferred over less symmetric faces (e.g. the symmetric faces on the bottom row of Figure 2) (Perrett et al., 1999; Rhodes et al., 1998). Measuring symmetry in real faces reveals a positive correlation with rated attractiveness (e.g. Grammer & Thornhill, 1994; Mealy et al., 1999; Penton-Voak et al., 2001).

Individual differences Having argued for the universality of attractive traits, we now examine some factors that may lead to individual differences in the perception of facial attractiveness and speculate on how such differences may arise from learning and differences in life history. Across the animal kingdom not all members of a given species engage in the same mating behaviour. Indeed, within a species there Birds of a feather?

29

January 2002 The Psychologist Vol 15 No 1 Presidents’ Award

humans focused on correlations in physical Research thus suggests that awareness tendency to develop a sexual aversion to characteristics between partners, such as of one’s own traits may encourage choice individuals with whom they live closely arm length. Reviews show an overall of partners similar to oneself. Seeking out in infancy and early childhood (usually pattern of low positive correlations (0.01 a partner who is similar to you, however, is siblings and parents). Originally proposed to 0.35) for many physical features (e.g. also consistent with attraction to parental as a mechanism for avoiding sibling incest, Spuhler, 1968). Married partners’ faces also traits, as usually children physically such negative imprinting would prevent resemble each other in ways that allow resemble their parents. This leads us to inbreeding in a population. Westermarck’s them to be identified as partners, possibly consider the influence of parental hypothesis has received empirical support indicating assortative mating for similar characteristics on mate preferences in from ethnographic studies where male and face shapes (e.g. Hinsz, 1989). humans. female non-siblings are raised together in Partners also appear to assort for many a way similar to real siblings (e.g. Shepher, non-physical traits such as religion, Attraction to parental traits 1971). Such individuals avoided marriage educational level and personality (Botwin In humans there have been few studies on or sexual relations with those with whom et al., 1997; Thiessen & Gregg, 1980). the effects of parental characteristics on the they were raised. Assortative mating may also simply result partner choice of offspring Ð although the Westermarck’s hypothesis concerns in more stable partnerships, as it has been idea of attraction to the opposite sex learning to avoid characteristics, but there shown that couples who are similar on parent’s form is a popular notion, mainly are studies that do indicate attraction to a variety of traits are less likely to break due to the speculation of psychoanalytic opposite-sex parental characteristics. Two up (Hill et al., 1976). theorists (e.g. Freud, 1927). In animals the studies have shown a positive correlation The above studies point to consistent effect of parental traits on later mate choice between father’s age and the daughter’s matching for a wide range of has received much attention. Imprinting partner’s age (Wilson & Barrett, 1987; characteristics among partners. Given this refers to a phenomenon whereby Zei et al., 1981). The positive relationship assortment, it is possible that individuals experience at an early age influences later between father’s and partner’s age is are attracted to others who resemble them behaviour including mate preferences. consistent with the possibility of imprinting physically. Self-similar attraction could be Konrad Lorenz (1943) drew attention to Ð daughters may imprint on the visual based on each person noticing his or her this phenomenon having found that characteristics of their father (such as their own traits. An experiment by Marion Petrie ducklings would imprint on and follow age) as children and later find these and colleagues has shown in peacocks that his patterned boots. Young animals see characteristics preferable in their own individuals appear to recognise kin without parental traits (such as plumage colour) partner. Although both studies are ever having seen any other members of at an early age, and later in life find these suggestive of sexual imprinting in humans, their family. They released a mixed group traits either unattractive or attractive in it should be noted that the correlations in of related and unrelated peacocks and mates. Attraction to parental characteristics both studies are small and account for little found that brothers raised separately has been demonstrated in a wide variety of of the variance in the data (in the Zei et al. established their display sites very close avian (see ten Cate & Vos, 1998) and study correlations are between 0.05 and together (Petrie et al., 1999). It is possible mammalian species (Kendrick et al., 1998). 0.08; in Wilson’s study the same that peacocks recognise kin by examining Imprinting has also been proposed as correlation is 0.11). their own body, and this is a potential playing a role in human mating, but in the A third study provides stronger mechanism for assortative mating for traits opposite direction. Westermarck (1894) evidence for imprinting-like effects in in other animals. argued that children have an innate humans. In a study of the spouse choices of individuals with parents of mixed ethnicity, Jedlicka (1980) found that spouse ethnicity corresponded to father’s ethnicity for 61.4 per cent of brides and 41.4 per cent of grooms. This relationship was reversed for mothers (mother’s and spouse’s ethnicity corresponded for 38.6 per cent of brides and 58.6 per cent of grooms). These results indicate that offspring were attracted to, or at least chose to marry, individuals who resembled their opposite-sex parent. Social pressures may provide additional constraints on ethnicity of marriage partners. For example, parents may encourage offspring to engage in relationships that reflect their own partner choices. To summarise, sexual imprinting may play a role in human mate choice Ð we may learn to avoid close relations, usually parents and siblings, but still show attraction to parental traits. Given the importance of imprinting in other species

30

The Psychologist Vol 15 No 1 January 2002 Presidents’ Award

and several suggestive studies on humans, FIGURE 3 shape) on the right. Overall, most young it would be interesting to further explore adult women find slightly feminised faces the role of parental influences on most attractive; but women at peak fertility attractiveness judgements in humans. are relatively more attracted to masculinised faces. Attractiveness of the beholder Male facial masculinity is proposed to The attractiveness of men and women’s be linked to good genes because such traits bodies will influence the mate they may reflect the action of testosterone, which is acquire and so is likely to impact on their an immuno-suppressant. Only males with mating strategy. Nancy Burley’s (1986) high-quality immune systems can afford work with zebra finches has demonstrated the testosterone handicap required to that manipulating the attractiveness of produce more masculine traits; so, as individuals using coloured leg bands with other species, masculine traits may changes the mating strategy they employ. there is an increased preference for advertise an individual’s immune quality The ‘attractiveness’ of the bands was masculinity and symmetry in male faces (see Thornhill & Gangestad, 1999). measured by their impact on the other for women who regard themselves as However, masculine partners may not make birds Ð some bands decreased the sexual attractive (Little et al., 2001). This finding ideal long-term partners: there is evidence attention received from opposite-sex birds, may reflect a condition-dependent mating that males with high testosterone are other bands increased it. strategy analogous to behaviour found in involved in more troubled relationships Zebra finches mate monogamously other species. and pursue more extra-marital affairs (see (both in the wild and in captivity) with Both masculinity and symmetry have Mazur & Booth, 1998). both males and females equally sharing been proposed to signal a high-quality Females may choose a long-term parental duties. But when Burley gave immune system and therefore markers for partner on the basis of co-operation and males ‘attractive’ leg bands they engaged in ‘good genes’. Such males may be better high parental care (indicated by a feminine polygamous mating, whereas those males for conferring immunity on children but appearance). By contrast, when a female is given green bands (unattractive) continued may be less inclined to invest in parental choosing a partner for a short-term to attempt to mate monogamously. Females duties (Thornhill & Gangestad, 1999). relationship (by definition one in which made attractive with coloured leg bands A preference for feminine asymmetric the male is not expected to make a were found to spend less time carrying out males could thus be adaptive for commitment) cues to paternal investment parental duties than both those typical of unattractive females, if the benefits of are irrelevant, and she should look to their sex and unattractive females Ð but increased paternal investment outweigh the maximise good gene benefits indicated by they still had higher reproductive success. loss of heritable genes for immune quality. a relatively masculine appearance. Not all Mates of attractive females spent more It is also possible that women who are women will need or value an investing time than those typical of their sex carrying of ‘high mate value’ (or who believe they partner (e.g. in some populations men may out parental duties. Again, higher are) may be more likely to attract and not play a large role in child rearing). In attractiveness allowed females to adjust retain a high mate value male (i.e. these instances an evolved psychology their strategy and induced partners to a masculine and symmetric male) than maximising preference for masculinity behave differently. a lower mate value female would. The (as an index of good genes for disease More recent work has indicated that perceiver’s attractiveness, then, is one immunity) over femininity (as an index physical condition may also influence an important between-individual variable in of investment) at peak fertility would be individual’s preferences as well as their judgements of facial attractiveness. It is adaptive. perceived attractiveness. For example, the also worth noting that it is a variable that red coloration of male sticklebacks can change due to accident, disease, or Conclusions decreases in intensity with parasite load, ageing Ð such changes may, as in zebra Evolutionary theory has proved to be and female sticklebacks demonstrate finches, radically alter an individual’s a powerful theoretical tool in exploring a preference for intense male coloration. sexual strategies and impact on their human facial attractiveness. Beauty Females in poor condition, however, show preferences. increasingly appears to be ingrained in an unexpected preference for less intensely our biology: characteristics associated coloured (i.e. poorer condition) males Within-individual changes with evolutionarily relevant advantages (Bakker et al., 1999). Recent research into male facial for the choosing individual are perceived So increases in attractiveness cause attractiveness has revealed that female as attractive. zebra finches to employ different preferences for male faces vary over the Individual differences in preferences reproductive tactics, and female condition menstrual cycle. Despite a preference for can be consistent with evolutionary theory. influences preferences in sticklebacks. feminine faces most of the time, during It is important to note that the factors Given these findings, it seems plausible to the follicular phase of the menstrual cycle presented here may not necessarily be postulate that attractive humans may be when conception is most likely, women adaptive, rather they may be able to adopt sexual strategies different prefer relatively masculine faces (Penton- epiphenomenal to other cognitive from those of unattractive individuals. In Voak et al., 1999; Penton-Voak & Perrett mechanisms that are adaptive. While some a recent study we explored how women’s 2000). In Figure 3, a composite of 20 male aspects of face perception appear innate, self-rated attractiveness influenced male faces has been ‘feminised’ (moved towards other aspects are clearly influenced by face-preference. Using faces manipulated a typical female shape) on the left, and experience; it seems unlikely that with computer graphics, we found that ‘masculinised’ (exaggerating typically male individuals are born with a representation

31

January 2002 The Psychologist Vol 15 No 1 Presidents’ Award

of what a perfect mate looks like. Hard- strategy, and therefore what is attractive, wired propensities to attend to face-like will depend on the individual. It is hoped stimuli early in life provide the opportunity that consideration of this ‘fine-grain’ of to learn the details of facial appearance, attractiveness will help to put beauty back and hence experience will shape facial in the eye of the beholder. aesthetic judgements. For humans, as with other species, there Anthony C. Little and David I. Perrett is no optimal strategy for mate choice and are at the School of Psychology, University parenting that applies to all individuals. of St Andrews, St Andrews, Fife KY16 9JU. Indeed the range of personal circumstances Tel: 01334 463044; fax: 01334 463042; (physical, environmental, social) will e-mail: [email protected], guarantee that what is a good or adequate [email protected].

References Bakker,T.C., Kunzler, R. & Mazzi, K. 395, 229–230. 20, 295–307. (1999). Condition-related mate Langlois, J.H., Kalakanis, L., Rubenstein, Perrett, D.I., Lee, K.J., Penton-Voak, I.S., choice in sticklebacks. Nature, A.J., Larson,A., Hallamm, M. & Rowland, D.R.,Yokishikawa, S., 401, 234. Smoot, M. (2000). Maxims or Burt, D.M. et al. (1998). Effects of Bateson, P.(1982). Preferences for myths of beauty? A meta-analytic sexual dimorphism on facial cousins in Japanese quail. Nature, and theoretical review. attractiveness. Nature, 394, 295, 236–237. Psychological Bulletin, 126, 884–887. Botwin, M.D., Buss, D.M. & 390–423. Petrie, M., Krupa,A. & Burke T. (1999). Shackelford,T.K. (1997). Little,A.C., Burt, D.M., Penton-Voak, I. Peacocks lek with relatives even Personality and mate preferences: & Perrett, D.I. (2001). in the absence of social and Five factors in mate selection and Self-perceived attractiveness environmental cues. Nature, 401, marital satisfaction. Journal of influences human female 155–157. Personality, 65, 107–136. preferences for sexual Rhodes, G., Proffitt, F., Grady, J. & Burley, N. (1983).The meaning of dimorphism and symmetry in Sumich,A. (1998). Facial assortative mating. Ethology and male faces. Proceedings of the Royal symmetry and the perception of Sociobiology, 4, 191–203. Society of London, B268, 39–44. beauty. Psychonomic Bulletin and Burley N. (1986). Sexual selection for Lorenz, K. (1943).The innate forms of Review, 5, 659–669. aesthetic traits in species with potential experience. Zeitschrift Shepher, J. (1971). Mate selection biparental care. American für Tierpsychologie, 5, 234–409. among second generation kibbutz Naturalist, 127, 415–445. Mazur,A. & Booth,A. (1998). adolescents and adults: Incest Buss, D.M. (1989). Sex differences in Testosterone and dominance in avoidance and negative human mate preferences: men. Behavioral and Brain Sciences, imprinting. Archives of Sexual Evolutionary hypotheses tested in 21, 353–371 Behavior, 1, 293–307. 37 cultures. Behavioural and Brain Mealy, L., Bridgestock, R. & Townsend, Spuhler, J.N. (1968).Assortative mating Sciences, 12, 1–49. G. (1999). Symmetry and with respect to physical Freud, S. (1927). Some psychological perceived facial attractiveness. characteristics. Eugenics Quarterly, consequences of the anatomical Journal of Personality and Social 15, 128–140. distinction between the sexes. Psychology, 76, 151–158. ten Cate C. & Vos D.R. (1999). International Journal of Møller,A.P.& Thornhill, R. (1998). Sexual imprinting and Psychoanalysis, 8, 133–142. Bilateral symmetry and sexual evolutionary processes in birds: Grammer, K. & Thornhill, R. (1994). selection:A meta-analysis. a reassessment. Advances in the Human (Homo sapiens) facial American Naturalist, 151, 174–192. Study of Behaviour, 28, 1–31. attractiveness and sexual Penton-Voak, I.S., Jones, B.C., Little, Thiessen, D. & Gregg B. (1980). selection: the role of symmetry A.C. Baker, S.,Tiddeman, B., Burt, and averageness. Journal of D.M. et al. (2001). Symmetry, Human assortative mating and Comparative Psychology, 108, sexual dimorphism in facial genetic equilibrium:An 233–242. proportions, and male facial evolutionary perspective. Ethology Hinsz,V.B. (1989). Facial resemblance attractiveness. Proceedings of the and Sociobiology, 1, 111–140. in engaged and married couples. Royal Society of London, B268, Thornhill, R. & Gangestad, S.W. Journal of Social and Personal 1617–1623. (1999). Facial attractiveness. Relationships, 6, 223–229. Penton-Voak, I.S., Perrett, D., Castles, Trends in Cognitive Sciences, 3, Hill, C.T., Rubzin, Z. & Peplau, L.A. D., Burt, D.M., Koyabashi,T., 452–460. (1976). Breakups before marriage: Murray, L.K. et al. (1999). Female Westermarck, E. (1894). The history of the end of 103 affairs. Journal of preferences for male faces change human marriage. London, Social Issues, 32, 147–168. cyclically. Nature, 399, 741–742. Macmillan. Hume, D. (1757). Four dissertations. IV: Penton-Voak, I.S. & Perrett, D.I. (2000). Wilson, G.D. & Barrett, P.T. (1987). Of the standard of taste. London: Female preference for male faces Parental characteristics and Millar. changes cyclically – Further partner choice: Some evidence Jedlicka, D. (1980).A test of the evidence. Evolution and Human for Oedipal imprinting. Journal of psychoanalytic theory of mate Behaviour, 21, 39–48. Biosocial Science, 19, 157–161. selection. Journal of Social Perrett, D.I., Burt, D.M., Penton-Voak, Zei, G.P., Astolifi, P.& Jayakar, S.D. Psychology, 112, 295–299. I.S., Lee, K.J., Rowland, D.R. & (1981). Correlation between Kendrick, K.M., Hinton, M.R. & Atkins, Edwards, R. (1999). Symmetry father’s age and husband’s age: K. (1998). Mothers determine and human facial attractiveness. A case of imprinting. Journal of male sexual preferences. Nature, Evolution and Human Behaviour, Biosocial Science, 13, 409–418.

32

The Psychologist Vol 15 No 1 January 2002