Menstrual cycle alters face preference

Through evolution's eyes: extracting mate preferences by linking visual attention to adaptive design

Information is crucial to decision-making, including mate choice decisions. Perceptual systems, such as attention, evolved in part to forage for reproductive information; consequently, these systems can be used to reveal mate preferences. Here, I consider the place of visual information in human mate choice and provide a rationale for pressing into service methods drawn from the attention literature for the study of mate choice decisions. Because visual attention is allocated automatically and selectively, it may be used to complement common methods of mate preference assessment, such as self-report questionnaires and measures of genital arousal, while avoiding some of the pitfalls of these methods. Beyond the utility of increasing confidence in extant research findings by employing relatively unobtrusive methods, visual attention paradigms can also allow researchers to explore a variety of questions that are rarely asked, such as those concerned with signal efficiency and tradeoffs in the assessment of mate value.

Effects of menstrual cycle phase on face preferences

While many studies of face preferences have emphasized high agreement among individuals about the types of faces they consider attractive and unattractive, other studies have demonstrated systematic variation in face preferences. Here, we review the evidence that women's preferences for masculinity, apparent health, and self-resemblance in faces change systematically during the menstrual cycle. Our review focuses on the proximate mechanisms that might underpin these changes (i.e., what changes in hormone levels are important for effects of menstrual cycle phase) and the possible functions of these changes (i.e., to maximize the likelihood that offspring inherit strong immune systems or to increase the likelihood of successful pregnancy by either promoting affiliation with individuals who will provide support and care during pregnancy or by promoting strategies to avoid contagion during social interactions). While evidence that differentiates between these two accounts of the function of cyclic shifts in face preferences is currently equivocal for masculinity preferences, there is compelling evidence that the function of the effects of menstrual cycle phase on preferences for apparent health and self-resemblance in faces is to increase the likelihood of successful pregnancy.

Social perception of facial resemblance in humans

Two lines of reasoning predict that highly social species will have mechanisms to influence behavior toward individuals depending on their degree of relatedness. First, inclusive fitness theory leads to the prediction that organisms will preferentially help closely related kin over more distantly related individuals. Second, evaluation of the relative costs and potential benefits of inbreeding suggests that the degree of kinship should also be considered when choosing a mate. In order to behaviorally discriminate between individuals with different levels of relatedness, organisms must be able to discriminate cues of kinship. Facial resemblance is one such potential cue in humans. Computer-graphic manipulation of face images has made it possible to experimentally test hypotheses about human kin recognition by facial phenotype matching. We review recent experimental evidence that humans respond to facial resemblance in ways consistent with inclusive fitness theory and considerations of the costs of inbreeding, namely by increasing prosocial behavior and positive attributions toward self-resembling images and selectively tempering attributions of attractiveness to other-sex faces in the context of a sexual relationship.

Preferences for symmetry in human faces in two cultures: data from the UK and the Hadza, an isolated group of hunter-gatherers

Many studies show agreement within and between cultures for general judgements of facial attractiveness. Few studies, however, have examined the attractiveness of specific traits and few have examined preferences in hunter-gatherers. The current study examined preferences for symmetry in both the UK and the Hadza, a hunter-gatherer society of Tanzania. We found that symmetry was more attractive than asymmetry across both the cultures and was more strongly preferred by the Hadza than in the UK. The different ecological conditions may play a role in generating this difference. Such variation in preference may be adaptive if it reflects adaptation to local conditions. Symmetry is thought to indicate genetic quality, which may be more important among the Hadza with much higher mortality rates from birth onwards. Hadza men who were more often named as good hunters placed a greater value on symmetry in female faces. These results suggest that high quality Hadza men are more discriminating in their choice of faces. Hadza women had increased preferences for symmetry in men's faces when they were pregnant or nursing, perhaps due to their increased discrimination and sensitivity to foods and disease harmful to a foetus or nursing infant. These results imply that symmetry is an evolutionarily relevant trait and that variation in symmetry preference appears strategic both between cultures and within individuals of a single culture.

Q-cgi: new techniques to assess variation in perception applied to facial attractiveness

We present novel methods for assessing variation in the perception of subjective cues based on a fusion of Q-methodology with computer graphics techniques. Participants first Q-sort face stimuli based upon a subjective quality; a randomization-based statistic is then calculated to test whether groups of participants differ in their perception. Computer graphics are then used to extract and illustrate the differences in the manner which participants sorted so that the differences can be quantified. As a demonstration, the technique is applied to investigate the effects of prospective relationship duration and of sexual restrictiveness on the characteristics which participants find attractive in photographs of opposite-sex faces. Results show that in a naturally varying set of faces, female participants prefer facial cues related to masculinity for short-term relationships, whereas characteristics related to positive personality attributes are preferred for long-term relationships. For short-term relationships, male participants appear to prefer more feminine, youthful faces. Preferences of individuals with less restricted sexual strategy paralleled short-term preferences in that more feminine female faces and more masculine male faces were preferred.

Does attractiveness in men provide clues to semen quality?

The psychological mechanisms underlying attractiveness judgements in humans are thought to be evolved adaptations for finding a high quality mate. The phenotype-linked fertility hypothesis proposes that females obtain reliable information on male fertility from male expression of sexual traits. A previous study of Spanish men reported that facial attractiveness was positively associated with semen quality. We aimed to determine whether this effect was widespread by examining a large sample of Australian men. We also extended our study to determine whether cues to semen quality are provided by components of attractiveness: masculinity, averageness and symmetry. Each male participant was photographed and provided a semen sample that was analyzed for sperm morphology, motility and concentration. Two independent sets of women rated the male photographs for attractiveness, and three further sets of 12 women rated the photographs for masculinity, symmetry or averageness. We found no significant correlations between semen quality parameters and attractiveness or attractive traits. Although male physical attractiveness may signal aspects of mate quality, our results suggest that phenotype-linked cues to male fertility may not be general across human populations.

Women's estradiol predicts preference for facial cues of men's testosterone

A growing body of research has shown that women express stronger attraction to more masculine traits when they are tested near ovulation than when tested during other times in the menstrual cycle. Although these effects have been interpreted as increased preferences for markers of elevated testosterone during times in the cycle when conception is most likely, no previous studies have directly demonstrated that women express stronger attraction to higher testosterone men at different times in the cycle. In addition, little research has addressed which hormonal or other physiological mechanisms may regulate temporal shifts in women's attractiveness judgments. In this research, we demonstrate that women with higher estradiol concentrations exhibit stronger preferences for the faces of men with higher testosterone concentrations, and that women's testosterone preference and estradiol curves track one another across days of the cycle. The findings are the first direct demonstration in humans that hormone concentrations in one sex are associated with attraction to cues of hormonal status in the opposite sex. The results support a functional role for estradiol in calibrating women's mating psychology to indices of their current fertility, analogous to similar processes that have been documented in nonhuman species. A strong correlation between estradiol and testosterone preference specifically during the luteal phase further suggests that women's mate preferences may track their fertility between different cycles in addition to being calibrated to the timing of ovulation within individual cycles.

Facial attractiveness: Variation, adaptiveness and consequences of facial preferences

This review embraces the following topics: intra- and inter-populational variation of facial preferences, relationship between facial attractiveness and mate value, biological and social effects of the perception of facial attractiveness, credibility of the adaptive perspective on facial preferences, and the phylogeny of facial attractiveness. Its main conclusions are as follows: (1) Many sources of inter-individual variation in assessments of facial attractiveness have been identified, e.g., the age, sex, biological quality, physiological state, personality, and living situation of the judge, as well as previously observed faces, physical similarity of the focal face to the judge's face, and acquaintance with and knowledge of the face owner. (2) Inter-populational consistency in perception of facial attractiveness is substantial and possesses both a biological and a cultural basis. (3) Facial attractiveness is a reliable cue to biological quality of the face owner, e.g., better parasite resistance, physical fitness, reproductive fitness, longevity, less mutational load, higher intelligence and better mental health. (4) Facially attractive people have more sexual partners, marry at a younger age, and remain single less frequently. Thereby, they have higher reproductive success than unattractive individuals. (5) As a whole, research supports the thesis that facial preferences are adaptive, that is, they evolved during the course of biological evolution because they assisted an individual in choosing a mate with good genes or a good personality.

Facial attractiveness: General patterns of facial preferences

This review covers universal patterns in facial preferences. Facial attractiveness has fascinated thinkers since antiquity, but has been the subject of intense scientific study for only the last quarter of a century. Many facial features contribute to facial attractiveness: Averageness and symmetry are preferred by males and females, probably because they signal genetic quality and developmental stability. Men prefer highly feminized female faces because they reflect high estrogen levels and low testosterone levels. This indicates that the woman is reproductively healthy. Women, on the other hand, prefer a moderate level of male facial masculinity, since facial masculinity that is too pronounced signals high level of testosterone and, thereby, a poorly developed pro-family personality. In women, facial hair is detrimental to facial attractiveness. In men, the effect is not consistent. Faces with a clear complexion are attractive to both men and women. Men prefer light and smooth skin in women. Positive facial expressions also enhance facial attractiveness. Many factors, in particular skin condition and facial proportions, affect perceived age, which is an important component of facial attractiveness. Men in particular strongly prefer youthful-looking female faces. Facial preferences enable an individual to recognize reproductively fit mates. Therefore, facial preferences are adaptive, although non-adaptive mechanisms related to general brain function also play a role.

Sex-contingent face aftereffects depend on perceptual category rather than structural encoding

Many studies have used visual adaptation to investigate how recent experience with faces influences perception. While faces similar to those seen during adaptation phases are typically perceived as more 'normal' after adaptation, it is possible to induce aftereffects in one direction for one category (e.g. female) and simultaneously induce aftereffects in the opposite direction for another category (e.g. male). Such aftereffects could reflect 'category-contingent' adaptation of neurons selective for perceptual category (e.g. male or female) or 'structure-contingent' adaptation of lower-level neurons coding the physical characteristics of different face patterns. We compared these explanations by testing for simultaneous opposite after effects following adaptation to (a) two groups of faces from distinct sex categories (male and female) or (b) two groups of faces from the same sex category (female and hyper-female) where the structural differences between the female and hyper-female groups were mathematically identical to those between male and female groups. We were able to induce opposite aftereffects following adaptation between sex categories but not after adaptation within a sex category. These findings indicate the involvement of neurons coding perceptual category in sex-contingent face aftereffects and cannot be explained by neurons coding only the physical aspects of face patterns.

Preferences for symmetry in faces change across the menstrual cycle

Symmetry in human male faces may be a cue to heritable fitness benefits and is found attractive. Preferences for facial masculinity, another proposed marker of genetic quality, have been found to vary in ways that may maximise evolutionary relevant benefits and masculinity is found to be of increased attractiveness at peak fertility across the menstrual cycle. Here we show that women prefer more symmetric faces at peak fertility (Study 1) and that such shifting preferences may be potentially strategic preferences as we found them to occur only for judgements concerning short-term relations and when women already had a partner (Study 2). Such preferences potentially indicate a strategy that maximises the quality of extra-pair/short-term partners or a quality dependent response to hormones. Such strategic preferences for symmetry may support the role of symmetry in signalling potential good-gene benefits.

Raised salivary testosterone in women is associated with increased attraction to masculine faces

Women's preferences for masculinity in men's faces, voices and behavioral displays change during the menstrual cycle and are strongest around ovulation. While previous findings suggest that change in progesterone level is an important hormonal mechanism for such variation, it is likely that changes in the levels of other hormones will also contribute to cyclic variation in masculinity preferences. Here we compared women's preferences for masculine faces at two points in the menstrual cycle where women differed in salivary testosterone, but not in salivary progesterone or estrogen. Preferences for masculinity were strongest when women's testosterone levels were relatively high. Our findings complement those from previous studies that show systematic variation in masculinity preferences during the menstrual cycle and suggest that change in testosterone level may play an important role in cyclic shifts in women's preferences for masculine traits.

Good genes, complementary genes and human mate preferences

The past decade has witnessed a rapidly growing interest in the biological basis of human mate choice. Here we review recent studies that demonstrate preferences for traits which might reveal genetic quality to prospective mates, with potential but still largely unknown influence on offspring fitness. These include studies assessing visual, olfactory and auditory preferences for potential good-gene indicator traits, such as dominance or bilateral symmetry. Individual differences in these robust preferences mainly arise through within and between individual variation in condition and reproductive status. Another set of studies have revealed preferences for traits indicating complementary genes, focussing on discrimination of dissimilarity at genes in the major histocompatibility complex (MHC). As in animal studies, we are only just beginning to understand how preferences for specific traits vary and inter-relate, how consideration of good and compatible genes can lead to substantial variability in individual mate choice decisions and how preferences expressed in one sensory modality may reflect those in another. Humans may be an ideal model species in which to explore these interesting complexities.

Why is muscularity sexy? Tests of the fitness indicator hypothesis

Evolutionary scientists propose that exaggerated secondary sexual characteristics are cues of genes that increase offspring viability or reproductive success. In six studies the hypothesis that muscularity is one such cue is tested. As predicted, women rate muscular men as sexier, more physically dominant and volatile, and less committed to their mates than nonmuscular men. Consistent with the inverted-U hypothesis of masculine traits, men with moderate muscularity are rated most attractive. Consistent with past research on fitness cues, across two measures, women indicate that their most recent short-term sex partners were more muscular than their other sex partners (ds = .36, .47). Across three studies, when controlling for other characteristics (e.g., body fat), muscular men rate their bodies as sexier to women (partial rs = .49-.62) and report more lifetime sex partners (partial rs = .20-.27), short-term partners (partial rs = .25-.28), and more affairs with mated women (partial r = .28).

Preferences for masculinity in male bodies change across the menstrual cycle

In human females cyclic shifts in preference have been documented for odour and physical and behavioral male traits. Women prefer the smell of dominant males, more masculine male faces and men behaving more dominantly when at peak fertility than at other times in their menstrual cycle. Here we examine variation in preferences for body sexual dimorphism. Across two studies, both between- and within-participant, we show that women prefer greater masculinity in male bodies at times when their fertility is likely highest, in the follicular phase of their cycle. Shifts were seen when rating for a short-term but not when rating for a long-term relationship. In line with studies showing similar effects for facial sexual dimorphism, we also show that women prefer greater masculinity when they think themselves attractive than when they think themselves less attractive. These results indicate that women's preferences for sexual dimorphism in male bodies follow a similar pattern as found for sexual dimorphism and dominance in other domains and such differences in preference may serve a similar function. Cyclic preferences could influence women to select partners when most likely to become pregnant that possess traits that may be most likely to maximize their offspring's quality via attraction to masculinity or serve to help acquire investment via attraction to femininity.

Social transmission of face preferences among humans

Previous studies demonstrating mate choice copying effects among females in non-human species have led many researchers to propose that social transmission of mate preferences may influence sexual selection for male traits. Although it has been suggested that social transmission may also influence mate preferences in humans, there is little empirical support for such effects. Here, we show that observing other women with smiling (i.e. positive) expressions looking at male faces increased women's preferences for those men to a greater extent than did observing women with neutral (i.e. relatively negative) expressions looking at male faces. By contrast, the reverse was true for male participants (i.e. observing women with neutral expressions looking at male faces increased male participant's preferences for those men to a greater extent than did observing women smiling at male faces). This latter finding suggests that within-sex competition promotes negative attitudes among men towards other men who are the target of positive social interest from women. Our findings demonstrate that social transmission of face preferences influences judgments of men's attractiveness, potentially demonstrating a mechanism for social transmission of mate preferences.

Altruists Attract

Explaining human cooperation continues to present a challenge because it goes beyond what is predicted by established theories of kinship and reciprocal altruism. Little attention has been paid to the sexual selection hypothesis that proposes that cooperation can act as a display that attracts mates. The costs of cooperating are then offset not by kinship or reciprocation but by increased mating success. Here we present results from a series of experiments which show that, as predicted by the sexual selection hypothesis, people preferentially direct cooperative behavior towards more attractive members of the opposite sex. Furthermore, cooperative behavior increases the perceived attractiveness of the cooperator. Economically costly behaviors can therefore bring benefits through mate choice and sexual selection should be regarded as an evolutionary mechanism capable of promoting cooperation.

Reproductive strategy, sexual development and attraction to facial characteristics

Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been associated with reproductive strategies. Stress during early development can retard or accelerate sexual maturation and reproduction. Early age of menarche is associated with absence of younger siblings, absence of a father figure during early life and increased weight. Father absence during early life is also associated with early marriage, pregnancy and divorce. Choice of partner characteristics is critical to successful implementation of sexual strategies. It has been suggested that sexually dimorphic traits (including those evident in the face) signal high-quality immune function and reproductive status. Masculinity in males has also been associated with low investment in mate and offspring. Thus, women's reproductive strategy should be matched to the probability of male investment, hence to male masculinity. Our review leads us to predict associations between the rate of sexual maturation and adult preferences for facial characteristics (enhanced sexual dimorphism and attractiveness). We find for men, engaging in sex at an early age is related to an increased preference for feminized female faces. Similarly, for women, the earlier the age of first sex the greater the preference for masculinity in opposite-sex faces. When we controlled sexual dimorphism in male faces, the speed of sexual development in women was not associated with differences in preference for male facial attractiveness. These developmental influences on partner choice were not mediated by self-rated attractiveness or parental relationships. We conclude that individuals assort in preferences based on the rapidity of their sexual development. Fast developing individuals prefer opposite-sex partners with an increased level of sexually dimorphic facial characteristics.

MHC-assortative facial preferences in humans

Individuals tend to choose mates who are sufficiently genetically dissimilar to avoid inbreeding. As facial attractiveness is a key factor in human mate preference, we investigated whether facial preferences were related to genetic dissimilarity. We asked female volunteers to rate the attractiveness of men from photographs and compared these results with individual genotypes at the major histocompatibility complex (MHC). In contrast to previously reported preferences based on odour, we found a non-significant tendency for women to rate MHC-similar faces as more attractive, suggesting a preference for cues to a self-similar MHC in faces. Further analysis revealed that male faces received higher attractiveness scores when rated by women who were MHC-similar than by MHC-dissimilar women. Although unexpected, this MHC-similar facial preference is consistent with other studies documenting assortative preferences in humans, including for facial phenotype.

Salience of emotional displays of danger and contagion in faces is enhanced when progesterone levels are raised

Findings from previous studies of hormone-mediated behavior in women suggest that raised progesterone level increases the probability of behaviors that will reduce the likelihood of disruption to fetal development during pregnancy (e.g. increased avoidance of sources of contagion). Here, we tested women's (N=52) sensitivity to potential cues to nearby sources of contagion (disgusted facial expressions with averted gaze) and nearby physical threat (fearful facial expressions with averted gaze) at two points in the menstrual cycle differing in progesterone level. Women demonstrated a greater tendency to perceive fearful and disgusted expressions with averted gaze as more intense than those with direct gaze when their progesterone level was relatively high. By contrast, change in progesterone level was not associated with any change in perceptions of happy expressions with direct and averted gaze, indicating that our findings for disgusted and fearful expressions were not due to a general response bias. Collectively, our findings suggest women are more sensitive to facial cues signalling nearby contagion and physical threat when raised progesterone level prepares the body for pregnancy.

Facial symmetry detection ability changes across the menstrual cycle

The effects of menstrual cycle phase and hormones on women's visual ability to detect symmetry and visual preference for symmetry were examined. Participants completed tests of symmetry detection and preference for male facial symmetry at two of three menstrual cycle phases (menses, periovulatory, and luteal). Women were better at detecting facial symmetry during the menses than luteal phase of their cycle. A trend indicated the opposite pattern for dot symmetry detection. Similarly, change in salivary progesterone levels across the cycle was negatively related to change in facial symmetry detection scores. However, there was no clear evidence of a greater preference for facial symmetry at any cycle phase, despite an overall preference for facial symmetry across phases. These findings suggest a menses phase advantage and a low progesterone advantage in women's ability to detect facial symmetry. The results are discussed in the context of hormonal, evolutionary mate selection, and functional neurocognitive theories.

Do Impressions of Health, Dominance, and Warmth Explain Why Masculine Faces are Preferred More in a Short-Term Mate?

Men high in facial masculinity are preferred more as a short-term partner (STP) than a long-term partner (LTP). We used a representative sample of natural faces to examine whether the greater preference for masculine-looking men as a STP could be explained by the fact that they look healthier, more dominant, or lower in warmth. None of these attributes explained the greater preference for facial masculinity in a STP. Rather, masculinity mediated the greater preference for healthy and dominant looking men as a STP. Women also preferred men who appeared high in warmth more as a LTP than a STP, an effect independent of facial masculinity, but mediated by facial expression. Our results suggest that women do not prefer masculine-looking men more as a STP than a LTP simply because they look healthier, more dominant, or less warm.

Early Psychosocial Stress Predicts Extra-Pair Copulations

Cheating on a mate, known as an extra-pair copulation (EPC), is considered unacceptable by most individuals. Nonetheless many individuals engage in such risky behaviors. Because individuals with high, as opposed to low, levels of early psychosocial stress are more risk prone and more likely to engage in opportunistic matings, we predicted that individuals reporting EPCs, one of many types of opportunistic mating (e.g., one-night stand, consecutive short-term relationships etc), have higher levels of early psychosocial stress than those who do not. Two types of EPCs were examined: EPC-self (EPC-S), having sex with someone other than one's mate, and EPC-other (EPC-O), having sex with someone else's mate. In a sample of 229 women and 161 men, significantly higher levels of early psychosocial stress were found amongst those reporting an EPC-S than those reporting none, irrespective of EPC-Os. Furthermore, the more EPC-Ss men, but not women, reported the higher their early psychosocial stress. Early psychosocial stress was not associated with EPC-Os irrespective of EPC-Ss. Participants were also classified into one of four groups (no EPCs, EPC-O only, EPC-S only, or EPC-S&O) which significantly interacted with early psychosocial stress. Results are discussed from adaptationist and mechanist perspectives and why early psychosocial stress was higher in individuals reporting EPC-Ss irrespective of EPC-Os, but not EPC-Os irrespective of EPC-Ss, than those not reporting the EPC of interest.

Reading men's faces: women's mate attractiveness judgments track men's testosterone and interest in infants

This study investigated whether women track possible cues of paternal and genetic quality in men's faces and then map perception of those cues onto mate attractiveness judgments. Men's testosterone concentrations served as a proxy for genetic quality given evidence that this hormone signals immunocompetence, and men's scores on an interest in infants test were chosen as prima facie markers of paternal quality. Women's perceptions of facial photographs of these men were in fact sensitive to these two variables: men's scores on the interest in infants test significantly predicted women's ratings of the photos for how much the men like children, and men's testosterone concentrations significantly predicted women's ratings of the men's faces for masculinity. Furthermore, men's actual and perceived affinity for children predicted women's long-term mate attractiveness judgments, while men's testosterone and perceived masculinity predicted women's short-term mate attractiveness judgments. These results suggest that women can detect facial cues of men's hormone concentrations and affinity for children, and that women use perception of these cues to form mate attractiveness judgments.

Sex similarities and differences in preferences for short-term mates: what, whether, and why

Are there sex differences in criteria for sexual relationships? The answer depends on what question a researcher asks. Data suggest that, whereas the sexes differ in whether they will enter short-term sexual relationships, they are more similar in what they prioritize in partners for such relationships. However, additional data and context of other findings and theory suggest different underlying reasons. In Studies 1 and 2, men and women were given varying "mate budgets" to design short-term mates and were asked whether they would actually mate with constructed partners. Study 3 used a mate-screening paradigm. Whereas women have been found to prioritize status in long-term mates, they instead (like men) prioritize physical attractiveness much like an economic necessity in short-term mates. Both sexes also show evidence of favoring well-rounded long- and short-term mates when given the chance. In Studies 4 and 5, participants report reasons for having casual sex and what they find physically attractive. For women, results generally support a good genes account of short-term mating, as per strategic pluralism theory (S. W. Gangestad & J. A. Simpson, 2000). Discussion addresses broader theoretical implications for mate preference, and the link between method and theory in examining social decision processes.

History and Current Concepts in the Analysis of Facial Attractiveness

BACKGROUND

Facial attractiveness research has yielded many discoveries in the past 30 years, and facial cosmetic, plastic, and reconstructive surgeons should have a thorough understanding of these findings. Many of the recent studies were conducted by social, developmental, cognitive, and evolutionary psychologists, and although the findings have been published in the psychology literature, they have not been presented in a comprehensive manner appropriate to surgeons.

METHODS

The author reviews the findings of facial attractiveness research from antiquity to the present day and highlights and analyzes important concepts necessary for a thorough understanding of facial attractiveness.

RESULTS

Four important cues emerge as being the most important determinants of attractiveness: averageness (prototypicality), sexual dimorphism, youthfulness, and symmetry.

CONCLUSIONS

A surgeon planning facial cosmetic, plastic, or reconstructive surgery can potentially gain both profound insight and better quality surgical results by appreciating these findings.

Effects of the menstrual cycle on looking preferences for faces in female rhesus monkeys

Fluctuations of ovarian hormones across the menstrual cycle influence a variety of social and cognitive behaviors in primates. For example, female rhesus monkeys exhibit heightened interest for males and increased agonistic interactions with other females during periods of high estrogen levels. In the present study, we hypothesized that females' preference for males during periods of high estrogen levels is also expressed at the level of face perception. We tested four intact females on two face-tasks involving neutral portraits of male and female rhesus monkeys, chimpanzees and humans. In the visual preference task (VP), monkeys had to touch a button to view a face image. The image remained on the screen as long as the button was touched, and the duration of pressing was taken as an index of the monkey's looking time for the face stimulus. In the Face-Delayed Recognition Span Test (Face-DRST), monkeys were rewarded for touching the new face in an increasing number of serially presented faces. Monkeys were tested 5 days a week across one menstrual cycle. Blood was collected every other day for analysis of estradiol and progesterone. Two of the four females were cycling at the time of testing. We did not find an influence of the cycle on Face-DRST, likely due to a floor effect. In the VP however, the two cycling individuals looked longer at conspecific male faces than female faces during the peri-ovulatory period of the cycle. Such effects were absent for human and chimpanzee faces and for the two noncycling subjects. These data suggest that ovarian hormones may influence females' preferences for specific faces, with heightened preference for male faces during the peri-ovulatory period of the cycle. Heightened interest for stimuli of significant reproductive relevance during periods of high conception risk may help guide social and sexual behavior in the rhesus monkey.

Correlated preferences for facial masculinity and ideal or actual partner's masculinity

Studies of women's preferences for male faces have variously reported preferences for masculine faces, preferences for feminine faces and no effect of masculinity-femininity on male facial attractiveness. It has been suggested that these apparently inconsistent findings are, at least partly, due to differences in the methods used to manipulate the masculinity of face images or individual differences in attraction to facial cues associated with youth. Here, however, we show that women's preferences for masculinity manipulated in male faces using techniques similar to the three most widely used methods are positively inter-related. We also show that women's preferences for masculine male faces are positively related to ratings of the masculinity of their actual partner and their ideal partner. Correlations with partner masculinity were independent of real and ideal partner age, which were not associated with facial masculinity preference. Collectively, these findings suggest that variability among studies in their findings for women's masculinity preferences reflects individual differences in attraction to masculinity rather than differences in the methods used to manufacture stimuli, and are important for the interpretation of previous and future studies of facial masculinity.

Sociosexuality in women and preference for facial masculinization and somatotype in men

Sociosexual orientation reflects individual differences in openness to short-term sexual relationships. We predicted that women with less restricted sociosexuality would be differentially attracted to highly masculinized male faces and bodies. In 2 studies, we investigated preference for male masculinization as a function of female sociosexuality. In Study 1, 40 female university students rated the attractiveness of pictures of male faces and somatotypes differing in masculinization level. All women preferred the faces with average levels of masculinity and the mesomorph somatotype; however, women with less restricted sociosexuality found the faces of men more attractive in general and showed relatively greater preference for masculinized bodies than did women with more restricted sociosexuality. In Study 2, 56 women met with 2 equally attractive male confederates, 1 highly masculinized and 1 less masculinized, in a "speed dating" scenario. After each date, women indicated their interest in each man for short-term and long-term relationships via questionnaire. In this more naturalistic context, sociosexuality was related to an increased interest for the more highly masculinized man in the context of short-term dating. Female sociosexuality appears to be related to preferences for higher levels of male masculinization.

Women's sexual interests across the ovulatory cycle depend on primary partner developmental instability

Normally ovulating women have been found to report greater sexual attraction to men other than their own partners when near ovulation relative to the luteal phase. One interpretation is that women possess adaptations to be attracted to men possessing (ancestral) markers of genetic fitness when near ovulation, which implies that women's interests should depend on qualities of her partner. In a sample of 54 couples, we found that women whose partners had high developmental instability (high fluctuating asymmetry) had greater attraction to men other than their partners, and less attraction to their own partners, when fertile.