Physical attractiveness

The degree of differences between male and female anatomical traits is called sexual dimorphism. Female respondents in the follicular phase of their menstrual cycle were significantly more likely to choose a masculine face than those in menses and luteal phases,[43] (or in those taking hormonal contraception).[19][20][44][45] This distinction supports the sexy son hypothesis, which posits that it is evolutionarily advantageous for women to select potential fathers who are more genetically attractive,[46] rather than the best caregivers.[47] However, women's likeliness to exert effort to view male faces does not seem to depend on their masculinity, but to a general increase with women's testosterone levels.[48]

It is suggested that the masculinity of facial features is a reliable indication of good health, or, alternatively, that masculine-looking males are more likely to achieve high status.[49] However, the correlation between attractive facial features and health has been questioned.[50] Sociocultural factors, such as self-perceived attractiveness, status in a relationship and degree of gender-conformity, have been reported to play a role in female preferences for male faces.[51] Studies have found that women who perceive themselves as physically attractive are more likely to choose men with masculine facial dimorphism, than are women who perceive themselves as physically unattractive.[52] In men, facial masculinity significantly correlates with facial symmetry—it has been suggested that both are signals of developmental stability and genetic health.[53] One study called into question the importance of facial masculinity in physical attractiveness in men, arguing that when perceived health, which is factored into facial masculinity, is discounted it makes little difference in physical attractiveness.[54] In a cross-country study involving 4,794 women in their early twenties, a difference was found in women's average "masculinity preference" between countries.[55]

A study found that the same genetic factors cause facial masculinity in both males and females such that a male with a more masculine face would likely have a sister with a more masculine face due to the siblings having shared genes. The study also found that, although female faces that were more feminine were judged to be more attractive, there was no association between male facial masculinity and male facial attractiveness for female judges. With these findings, the study reasoned that if a woman were to reproduce with a man with a more masculine face, then her daughters would also inherit a more masculine face, making the daughters less attractive. The study concluded that there must be other factors that advantage the genetics for masculine male faces to offset their reproductive disadvantage in terms of "health", "fertility" and "facial attractiveness" when the same genetics are present in females. The study reasoned that the "selective advantage" for masculine male faces must "have (or had)" been due to some factor that is not directly tied to female perceptions of male facial attractiveness.[56]

In a study of 447 gay men in China, researchers said that tops preferred feminized male faces, bottoms preferred masculinized male faces and versatiles had no preference for either feminized or masculinized male faces.[57]

In pre-modern Chinese literature, the ideal man in caizi jiaren romances was said to have "rosy lips, sparkling white teeth" and a "jasper-like face" (Chinese: 唇紅齒白、面若冠玉).[58][59]

In Middle English literature, a beautiful man should have a long, broad and strong face.[60]

A study that used Chinese, Malay and Indian judges said that Chinese men with orthognathism where the mouth is flat and in-line with the rest of the face were judged to be the most attractive and Chinese men with a protruding mandible where the jaw projects outward were judged to be the least attractive.[61]

Symmetrical faces and bodies may be signs of good inheritance to women of child-bearing age seeking to create healthy offspring. Studies suggest women are less attracted to men with asymmetrical faces,[62] and symmetrical faces correlate with long term mental performance[63] and are an indication that a man has experienced "fewer genetic and environmental disturbances such as diseases, toxins, malnutrition or genetic mutations" while growing.[63] Since achieving symmetry is a difficult task during human growth, requiring billions of cell reproductions while maintaining a parallel structure, achieving symmetry is a visible signal of genetic health.

Studies have also suggested that women at peak fertility were more likely to fantasize about men with greater facial symmetry,[64] and other studies have found that male symmetry was the only factor that could significantly predict the likelihood of a woman experiencing orgasm during sex. Women with partners possessing greater symmetry reported significantly more copulatory female orgasms than were reported by women with partners possessing low symmetry, even with many potential confounding variables controlled.[65] This finding has been found to hold across different cultures. It has been argued that masculine facial dimorphism (in men) and symmetry in faces are signals advertising genetic quality in potential mates.[66] Low facial and body fluctuating asymmetry may indicate good health and intelligence, which are desirable features.[67] Studies have found that women who perceive themselves as being more physically attractive are more likely to favor men with a higher degree of facial symmetry, than are women who perceive themselves as being less physically attractive.[52] It has been found that symmetrical men (and women) have a tendency to begin to have sexual intercourse at an earlier age, to have more sexual partners, and to have more one-night stands. They are also more likely to be prone to infidelity.[68] A study of quarterbacks in the American National Football League found a positive correlation between facial symmetry and salaries.[26]

Double-blind studies found that women prefer the scent of men who are rated as facially attractive.[69] For example, both males and females were more attracted to the natural scent of individuals who had been rated by consensus as facially attractive.[70] Additionally, it has also been shown that women have a preference for the scent of men with more symmetrical faces, and that women's preference for the scent of more symmetrical men is strongest during the most fertile period of their menstrual cycle.[71] Within the set of normally cycling women, individual women's preference for the scent of men with high facial symmetry correlated with their probability of conception.[71] Men's body odor is also affected by their diet, with women expressing preferences for male body odor associated with increased dietary fruit and vegetable and protein content, and reduced carbohydrate content.[72]

Studies have explored the genetic basis behind such issues as facial symmetry and body scent and how they influence physical attraction. In one study in which women wore men's T-shirts, researchers found that women were more attracted to the bodily scents in shirts of men who had a different type of gene section within the DNA called major histocompatibility complex (MHC).[73] MHC is a large gene area within the DNA of vertebrates which encodes proteins dealing with the immune system[74] and which influences individual bodily odors.[75] One hypothesis is that humans are naturally attracted by the sense of smell and taste to others with dissimilar MHC sections, perhaps to avoid subsequent inbreeding while increasing the genetic diversity of offspring.[74] Furthermore, there are studies showing that women's natural attraction for men with dissimilar immune profiles can be distorted with use of birth control pills.[75] Other research findings involving the genetic foundations of attraction suggest that MHC heterozygosity positively correlates with male facial attractiveness. Women judge the faces of men who are heterozygous at all three MHC loci to be more attractive than the faces of men who are homozygous at one or more of these loci. Additionally, a second experiment with genotyped women raters, found these preferences were independent of the degree of MHC similarity between the men and the female rater. With MHC heterozygosity independently seen as a genetic advantage, the results suggest that facial attractiveness in men may be a measure of genetic quality.[76][77] General genetic heterozygosity has been demonstrated to be related to attractiveness in that people with mixed genetic backgrounds (i.e., mixed race people) as seen as more attractive than people with a more similar genetic parents. (i.e., single race people).[78] However, some studies have not found that mixed race individuals are rated as more attractive, and one found that only certain mixes were rated as more attractive; this study argued that equating race with genetics was incorrect and argued for social influences as the cause.[79]

A 2010 OkCupid study on 200,000 of its male and female dating site users found that women are, except those during their early to mid-twenties, open to relationships with both somewhat older and somewhat younger men; they have a larger potential dating pool than men until age 26. At age 20, women, in a "dramatic change", begin sending private messages to significantly older men. At age 29, they become "even more open to older men". Male desirability to women peaks in the late 20s and does not fall below the average for all men until 36.[80] Other research indicates that women, irrespective of their own age, are attracted to men who are the same age or older.[81]

For the Romans especially, "beardlessness" and "smooth young bodies" were considered beautiful to both men and women.[82] For Greek and Roman men, the most desirable traits of boys were their "youth" and "hairlessness". Pubescent boys were considered a socially appropriate object of male desire, while post-pubescent boys were considered to be "ἔξωροι" or "past the prime".[82] This was largely in the context of pederasty (adult male interest in adolescent boys). Today, men and women's attitudes towards male beauty has changed. For example, body hair on men may even be preferred (see below).

A 1984 study said that gay men tend to prefer gay men of the same age as ideal partners, but there was a statistically significant effect (p < 0.05) of masculinity-femininity. The study said that more feminine men tended to prefer relatively older men than themselves and more masculine men tended to prefer relatively younger men than themselves.[83]

The physique of a slim waist, broad shoulders and muscular chest are often found to be attractive to both females and males.[84] Further research has shown that, when choosing a mate, the traits females look for indicate higher social status, such as dominance, resources, and protection.[85] An indicator of health in males (a contributing factor to physical attractiveness) is the android fat distribution pattern which is categorized as more fat distributed on the upper body and abdomen, commonly referred to as the "V shape."[85] When asked to rate other men, both heterosexual and homosexual men found low waist-to-chest ratios (WCR) to be more attractive on other men, with the gay men showing a preference for lower WCR (more V-shaped) than the straight men.[86]

Other researchers found waist-to-chest ratio the largest determinant of male attractiveness, with body mass index and waist-to-hip ratio not as significant.[87]

Women focus primarily on the ratio waist to chest or more specifically waist to shoulder. This is analogous to the waist to hip ratio (WHR) that men prefer. Key body image for a man in the eyes of a woman would include big shoulders, chest, and upper back, and a slim waist area.[88] Research has additionally shown that college males had a better satisfaction with their body than college females.[89] The research also found that when a college female's waist to hip ratio went up, their body image satisfaction decreased.[89]

Some research has shown that body weight may have a stronger effect than WHR when it comes to perceiving attractiveness of the opposite sex. It was found that waist to hip ratio played a smaller role in body preference than body weight in regards to both sexes.[90]

Psychologists Viren Swami and Martin J. Tovee compared female preference for male attractiveness cross culturally, between Britain and Malaysia. They found that females placed more importance on WCR (and therefore body shape) in urban areas of Britain and Malaysia, while females in rural areas placed more importance on BMI (therefore weight and body size). Both WCR and BMI are indicative of male status and ability to provide for offspring, as noted by evolutionary theory.[91]

Females have been found to desire males that are normal weight and have the average WHR for a male. Females view these males as attractive and healthy. Males who had the average WHR but were overweight or underweight are not perceived as attractive to females. This suggests that WHR is not a major factor in male attractiveness, but a combination of body weight and a typical male WHR seem to be the most attractive. Research has shown that men who have a higher waist to hip ratio and a higher salary are perceived as more attractive to women.[92]

A 1982 study found that an abdomen that protrudes was the "least attractive" trait for men.[93]

In Middle English literature, a beautiful man should have a flat abdomen.[60]

Men's bodies portrayed in magazines marketed to men are more muscular than the men's bodies portrayed in magazines marketed to women. From this, some have concluded that men perceive a more muscular male body to be ideal, as distinct from a woman's ideal male, which is less muscular than what men perceive to be ideal.[94] This is due to the within-gender prestige granted by increased muscularity and within-gender competition for increased muscularity.[94] Men perceive the attractiveness of their own musculature by how closely their bodies resemble the "muscle man."[95] This "muscle man" ideal is characterized by large muscular arms, especially biceps, a large muscular chest that tapers to their waist and broad shoulders.[95] Among Australian university students, the male body composition found to be most attractive (12.16 kg fat, 63.27 kg muscle) was in line with the composition that was perceived as healthiest, and was well within the healthy range.[96]

In a study of stated profile preferences on Match.com, a greater percentage of gay men than lesbians selected their ideal partner's body type as "Athletic and Toned" as opposed to the other two options of "Average" or "Overweight".[97]

In pre-modern Chinese literature, such as in Romance of the Western Chamber, a type of masculinity called "scholar masculinity" is depicted wherein the "ideal male lover" is "weak, vulnerable, feminine, and pedantic".[58]

In Middle English literature, a beautiful man typically has thick, broad shoulders, a square and muscular chest, a muscular back, strong sides that taper to a small waist, large hands and arms and legs with huge muscles.[60]

A 2006 study, of 25,594 heterosexual men found that "men who perceived themselves as having a large penis were more satisfied with their own appearance".[98]

A 2014 study criticized previous studies based on the fact that they relied on images and used terms such as "small", "medium", and "large" when asking for female preference. The new study used 3D models of penises from sizes of 4 inches (10 cm) long and 2.5 inches (6.4 cm) in circumference to 8.5 inches (22 cm) long and 7 inches (18 cm) in circumference and let the women "view and handle" them. It was found that women overestimated the actual size of the penises they have experimented with when asked in a follow-up survey. The study concluded that "women on average preferred the 6.5-inch (17 cm) penis in length both for long-term and for one-time partners. Penises with larger girth were preferred for one-time partners."[99]

This drawing of two male figures is a remake of the drawing of the leg-to-body ratio (LBR) extremes used in the experiment by Swami et al. (2006) to find out what LBR is considered the most attractive for men and women. The figure with the lowest LBR and shortest legs at left had the highest average attractiveness ratings whereas the male figure with the highest LBR and longest legs at right had the lowest ratings from British men and women.[100]

"Leg-to-body ratio" is seen as indicator of physical attractiveness but there appears to be no accepted definition of leg-length: the 'perineum to floor' measure[lower-alpha 1] is the most used but arguably the distance from ankle bone to outer hip bone is more rigorous.[101] On this (latter) metric, the most attractive ratio of leg to body for men (as seen by American women) is 1:1.[101] A Japanese study using the former metric found the same result for male attractiveness but women with longer legs than body were judged to be more attractive.[102] Excessive deviations from the mean were seen as indicative of disease.[102]

Females' sexual attraction towards males may be determined by the height of the man.[103] The online dating Website eHarmony only matches women with men taller than they themselves, because of complaints from women matched with shorter men.[104]

Other studies have shown that heterosexual women often prefer men taller than they are rather than a man with above average height. While women usually desire men to be at least the same height as themselves or taller, several other factors also determine male attractiveness, and the male-taller norm is not universal.[105] For example, taller women are more likely to relax the "taller male" norm than shorter women.[106] Furthermore, professor Adam Eyre-Walker, from the University of Sussex, has stated that there is, as yet, no evidence that these preferences are evolutionary preferences, as opposed to merely cultural preferences.[107] Still, the cultural perceived attractiveness preferences for taller men are powerful and confirmed by multiple studies. One study by Stulp found that "women were most likely to choose a speed-dater 25 cm taller than themselves."[108]

Additionally, women seem more receptive to an erect posture than men, though both prefer it as an element within beauty.[109] According to one study (Yee N., 2002), gay men who identify as "only tops" tend to prefer shorter men, while gay men who identify as "only bottoms" tend to prefer taller men.[110]

In romances in Middle English literature, all of the "ideal" male heroes are tall, and the vast majority of the "valiant" male heroes are tall too.[60]

Studies based in the United States, New Zealand, and China have shown that women rate men with no trunk (chest and abdominal) hair as most attractive, and that attractiveness ratings decline as hairiness increases.[111][112] Another study, however, found that moderate amounts of trunk hair on men was most attractive, to the sample of British and Sri Lankan women.[113] Further, a degree of hirsuteness (hairiness) and a waist-to-shoulder ratio of 0.6 is often preferred when combined with a muscular physique.[113]

In a study using Finnish women, women with hairy fathers were more likely to prefer hairy men, suggesting that preference for hairy men is the result of either genetics or imprinting.[114] Among gay men, another study (Yee N., 2002) reported gay males who identify as "only tops" prefer less hairy men, while gay males who identify as "only bottoms" prefer hairier men.[110]

Manual laborers who spent extended periods of time outside developed a darker skin tone due to exposure to the sun. As a consequence, an association between dark skin and the lower classes developed. Light skin became an aesthetic ideal because it symbolized wealth. "Over time society attached various meanings to these colored differences. Including assumptions about a person's race, socioeconomic class, intelligence, and physical attractiveness."[115]

A scientific review published in 2011, identified from a vast body of empirical research that skin colour as well as skin tone tend to be preferred as they act as indicators of good health. More specifically, these indicators are thought to suggest to potential mates that the beholder has strong or good genes capable of fighting off disease.[116]

More recent research has suggested that redder and yellower skin tones,[117] reflecting higher levels of oxygenated blood,[118] carotenoid and to a lesser extent melanin pigment, and net dietary intakes of fruit and vegetables,[119] appear healthier, and therefore more attractive.[120]

A University of Toronto study found that the facial proportions of Jessica Alba were close to the average of all female profiles.

Namie Amuro inspired the small-face fad in Japan which caused Japanese women to buy beauty products such as masks and creams to try to obtain a small face like hers.[125]

Research has attempted to determine which facial features communicate attractiveness. Facial symmetry has been shown to be considered attractive in women,[126][127] and men have been found to prefer full lips,[128] high forehead, broad face, small chin, small nose, short and narrow jaw, high cheekbones,[62][129] clear and smooth skin, and wide-set eyes.[121] The shape of the face in terms of "how everything hangs together" is an important determinant of beauty.[130] Women with thick, dark limbal rings in their eyes have also been found to be more attractive. The explanation given is that because the ring tends to fade with age and medical problems, a prominent limbal ring gives an honest indicator of youth.[131]

In Persian literature, beautiful women are said to have noses like hazelnuts.[132] In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to have straight and fine noses.[133] In Jewish Rabbinic literature, the rabbis considered a delicate nose to be the ideal type of nose for women.[134] In Japan, during the Edo period, a component of the female beauty ideal was for women to have tall noses which were straight and not "too tall".[135]

In a cross-cultural study, more neotenized (i.e., youthful looking) female faces were found to be most attractive to men while less neotenized female faces were found to be less attractive to men, regardless of the females' actual age.[136] In a study of Italian women who have won beauty competitions, it was found that their faces had more "babyish" (pedomorphic) traits than those of the "normal" women used as a reference.[137]

In a cross-cultural study, Marcinkowska et al. said that 18- to 45-year-old heterosexual men in all 28 countries surveyed preferred photographs of 18- to 24-year-old white women whose faces were feminized using Psychomorph software over faces of 18- to 24-year-old white women that were masculinized using that software, but there were differences in preferences for femininity across countries. The higher the National Health Index of a country, the more were the feminized faces preferred over the masculinized faces. Among the countries surveyed, Japan had the highest femininity preference and Nepal had the lowest femininity preference.[138]

Michael R. Cunningham of the Department of Psychology at the University of Louisville found, using a panel of East Asian, Hispanic and White judges, that the Asian, Hispanic and White female faces found most attractive were those that had "neonate large eyes, greater distance between eyes, and small noses"[139] and his study led him to conclude that "large eyes" were the most "effective" of the "neonate cues".[139] Cunningham also said that "shiny" hair may be indicative of "neonate vitality".[139] Using a panel of blacks and whites as judges, Cunningham found more neotenous faces were perceived as having both higher "femininity" and "sociability".[139] In contrast, Cunningham found that faces that were "low in neoteny" were judged as "intimidating".[139] Cunningham noted a "difference" in the preferences of Asian and white judges with Asian judges preferring women with "less mature faces" and smaller mouths than the White judges.[139] Cunningham hypothesized that this difference in preference may stem from "ethnocentrism" since "Asian faces possess those qualities", so Cunningham re-analyzed the data with "11 Asian targets excluded" and concluded that "ethnocentrism was not a primary determinant of Asian preferences."[139] Rather than finding evidence for purely "neonate" faces being most appealing, Cunningham found faces with "sexually-mature" features at the "periphery" of the face combined with "neonate" features in the "center of the face" most appealing in men and women.[139] Upon analyzing the results of his study, Cunningham concluded that preference for "neonate features may display the least cross-cultural variability" in terms of "attractiveness ratings"[139] and, in another study, Cunningham concluded that there exists a large agreement on the characteristics of an attractive face.[140][141]

In computer face averaging tests, women with averaged faces have been shown to be considered more attractive.[28][142] This is possibly due to average features being more familiar and, therefore, more comfortable.[126]

Commenting on the prevalence of whiteness in supposed beauty ideals in his book White Lies: Race and the Myth of Whiteness, Maurice Berger states that the schematic rendering in the idealized face of a study conducted with American subjects had "straight hair," "light skin," "almond-shaped eyes," "thin, arched eyebrows," "a long, thin nose, closely set and tiny nostrils" and "a large mouth and thin lips",[143] though the author of the study stated that there was consistency between his results and those conducted on other races. Scholar Liu Jieyu says in the article White Collar Beauties, "The criterion of beauty is both arbitrary and gendered. The implicit consensus is that women who have fair skin and a slim figure with symmetrical facial features are pretty." He says that all of these requirements are socially constructed and force people to change themselves to fit these criteria.[144]

One psychologist speculated there were two opposing principles of female beauty: prettiness and rarity. So on average, symmetrical features are one ideal, while unusual, stand-out features are another.[145] A study performed by the University of Toronto found that the most attractive facial dimensions were those found in the average female face. However, that particular University of Toronto study looked only at white women.[146]

A study that used Chinese, Malay and Indian judges said that Chinese women with orthognathism where the mouth is flat and in-line with the rest of the face were judged to be the most attractive and Chinese women with a protruding mandible where the jaw projects outward were judged to be the least attractive.[61]

A 2011 study, by Wilkins, Chan and Kaiser found correlations between perceived femininity and attractiveness, that is, women's faces which were seen as more feminine were judged by both men and women to be more attractive.[147]

A component of the female beauty ideal in Persian literature is for women to have faces like a full moon.[132][148][149]

In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to have round faces which were like a "full moon".[133]

In Japan, during the Edo period, a component of the female beauty ideal was for women to have long and narrow faces which were shaped like ovals.[135]

In Jewish Rabbinic literature, the rabbis considered full lips to be the ideal type of lips for women.[134]

Historically, in Chinese and Japanese literature, the feminine ideal was said to include small lips.[150] Women would paint their lips thinner and narrower to align with this ideal.[151][152]

Classical Persian literature, paintings, and miniatures portrayed traits such as long black curly hair, a small mouth, long arched eyebrows, large almond shaped eyes, a small nose, and beauty spots as being beautiful for women.[153]

Through the East Asian blepharoplasty cosmetic surgery procedure, Asian women can permanently alter the structure of their eyelid. Some people have argued that this alteration is done to resemble the structure of a Western eyelid[154] while other people have argued that this is generally done solely to emulate the appearance of naturally occurring Asian double eyelids.[155]

A study that investigated whether or not an eyelid crease makes Chinese-descent women more attractive using photo-manipulated photographs of young Chinese-descent women's eyes found that the "medium upper eyelid crease" was considered most attractive by all three groups of both sexes: white people, Chinese and Taiwanese nationals together as a group, and Taiwanese and Chinese Americans together as a group. Similarly, all three groups of both genders found the absence of an eye crease to be least attractive on Chinese women.[156]

In the late sixteenth century, Japanese people considered epicanthic folds to be beautiful.[157]

A study that used Russian, American, Brazilian, Aché, and Hiwi raters, found that the only strong distinguisher between men and women's faces was wider eyes relative to facial height for women, and this trait consistently predicted attractiveness ratings for women.[158]

In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to have dark black eyes which are large and long and in the shape of almonds. Furthermore, the eyes should be lustrous, and they should have long eyelashes.[133]

A source written in 1823, said that a component of the Persian female beauty ideal was for women to have large eyes which are black in color.[148] In Persian literature, beautiful women are said to have eyes that are shaped like almonds.[132]

In Chinese, the phrase "lucent irises, lustrous teeth" (Chinese: 明眸皓齒) is used to describe a beautiful woman with "clear eyes" and "well-aligned, white teeth", and the phrase "moth-feeler eyebrows" (Chinese: 蛾眉) is used to denote a beautiful woman by describing her eyebrows as being thin and arched like moth antennae. In the Chinese text The Grotto of the Immortals (Chinese: 遊仙窟) written during the Tang dynasty period, narrow eyes were the preferred type of eyes for women, and, in the Chinese text Jeweled Chamber Secrets (Chinese: 玉房秘訣) from the Six Dynasties period, the ideal woman was described as having small eyes.[135]

In Japan, during the Edo period, one piece of evidence, the appearance of the "formal wife" of Tokugawa Iesada as determined by "bone anthropologist" Suzuki Hisashi, indicates that large eyes were considered attractive for women, but, another piece of evidence, the 1813 Japanese text Customs, Manners, and Fashions of the Capital (Japanese: 都風俗化粧伝), indicates that large eyes were not considered attractive for women.[135]

Cross-cultural data shows that the reproductive success of women is tied to their youth and physical attractiveness[159] such as the pre-industrial Sami where the most reproductively successful women were 15 years younger than their man.[160] One study covering 37 cultures showed that, on average, a woman was 2.5 years younger than her male partner, with the age difference in Nigeria and Zambia being at the far extreme of 6.5 to 7.5 years. As men age, they tend to seek a mate who is ever younger.[121]

25% of eHarmony's male customers over the age of 50 request to only be matched with women younger than 40.[104] A 2010 OkCupid study, of 200,000 users found that female desirability to its male users peaks at age 21, and falls below the average for all women at 31. After age 26, men have a larger potential dating pool than women on the site; and by age 48, their pool is almost twice as large. The median 31-year-old male user searches for women aged 22 to 35, while the median 42-year-old male searches for women 27 to 45. The age skew is even greater with messages to other users; the median 30-year-old male messages teenage girls as often as women his own age, while mostly ignoring women a few years older than him. Excluding the 10% most and 10% least beautiful of women, however, women's attractiveness does not change between 18 and 40, but if extremes are not excluded "There's no doubt that younger [women] are more physically attractive—indeed in many ways beauty and youth are inextricable. That's why most of the models you see in magazines are teenagers".[80]

Pheromones (detected by female hormone markers) reflects female fertility and the reproductive value mean.[161] As females age, the estrogen-to-androgen production ratio changes and results in female faces to appear more and more masculine (thus appearing less "attractive").[161] In a small (n=148) study performed in the United States, using male college students at one university, the mean age expressed as ideal for a wife was found to be 16.87 years old, while 17.76 was the mean ideal age for a brief sexual encounter. However, the study sets up a framework where "taboos against sex with young girls" are purposely diminished, and biased their sample by removing any participant over the age of 30, with a mean participant age of 19.83.[162] In a study of penile tumescence, men were found most aroused by pictures of young adult females.[163]

Signals of fertility in women are often also seen as signals of youth. The evolutionary perspective proposes the idea that when it comes to sexual reproduction, the minimal parental investment required by men gives them the ability and want to simply reproduce 'as much as possible.'[164] It therefore makes sense that men are attracted to the features in women which signal youthfulness, and thus fertility.[164] Their chances of reproductive success are much higher than they would be should they pick someone older—and therefore less fertile.

This may explain why combating age declines in attractiveness occurs from a younger age in women than in men. For example, the removal of one's body hair is considered a very feminine thing to do.[165] This can be explained by the fact that aging results in raised levels of testosterone and thus, body hair growth. Shaving reverts one's appearance to a more youthful stage[165] and although this may not be an honest signal, men will interpret this as a reflection of increased fertile value. Research supports this, showing hairlessness to considered sexually attractive by men.[166]

Research has shown that most heterosexual men enjoy the sight of female breasts,[167] with a preference for large, firm breasts.[168] However, a contradictory study of British undergraduates found younger men preferred small breasts on women.[169] Smaller breasts were widely associated with youthfulness.[170] Cross-culturally, another study found "high variability" regarding the ideal breast size.[169] Some researchers in the United Kingdom have speculated that a preference for larger breasts may have developed in Western societies because women with larger breasts tend to have higher levels of the hormones estradiol and progesterone, which both promote fertility.[171]

A study by Groyecka et al., in which they examined Poles and Yali of New Guinea, demonstrated that men judgements of breast appearance is affected by the occurrence of breast ptosis (i.e., sagginess, droopiness).[172] Greater breast ptosis (more sagging breasts) is perceived as less attractive and attributed to a woman of older age. These findings are coherent with previous research that link breast attractiveness with female youthfulness. Unlike breast size, breast ptosis seems to be a universal marker of female breast attractiveness.

A study showed that men prefer symmetrical breasts.[123][173] Breast symmetry may be particularly sensitive to developmental disturbances and the symmetry differences for breasts are large compared to other body parts. Women who have more symmetrical breasts tend to have more children.[174]

Historical literature often includes specific features of individuals or a gender that are considered desirable. These have often become a matter of convention, and should be interpreted with caution. In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to have small breasts.[133] In Persian literature, beautiful women are said to have breasts like pomegranates or lemons.[132] In the Chinese text Jeweled Chamber Secrets (Chinese: 玉房秘訣) from the Six Dynasties period, the ideal woman was described as having firm breasts.[135] In Sanskrit literature, beautiful women are often said to have breasts so large that they cause the women to bend a little bit from their weight.[175] In Middle English literature, beautiful women should have small breasts that are round like an apple or a pear.[60]

This drawing is a remake of a drawing used in an experiment to research what South African, British white and British African men considered to be the most attractive size of posterior and breasts for white and black women. This image only shows the two extreme variations of size on black female figures used in the experiment. The figure at left received the highest average attractiveness rating from South African men while a figure with an intermediate size received the highest ratings from both white and black British men. The figure at right did not receive the highest average attractiveness rating from any group.[176]

Biological anthropologist Helen E. Fisher of the Center for Human Evolution Studies in the Department of Anthropology of Rutgers University said that, "perhaps, the fleshy, rounded buttocks... attracted males during rear-entry intercourse."[177] In a recent study, using 3D models and eye-tracking technology Fisher's claim was tested and was shown that the slight thrusting out of a woman's back influence how attractive others perceive her to be and captures the gaze of both men and women.[178][179] Bobbi S. Low et al. of the School of Natural Resources and Environment at the University of Michigan, said the female "buttocks evolved in the context of females competing for the attention and parental commitment of powerful resource-controlling males" as an "honest display of fat reserves" that could not be confused with another type of tissue,[180] although T. M. Caro, professor in the Center for Population Biology and the Department of Wildlife, Fish, and Conservation Biology, at University of California, Davis, rejected that as being a necessary conclusion, stating that female fatty deposits on the hips improve "individual fitness of the female", regardless of sexual selection.[180]

In a 1995 study, black men were more likely than white men to use the words "big" or "large" to describe their conception of an attractive woman's posterior.[181]

Body Mass Index (BMI) is an important determinant to the perception of beauty.[182] Even though the Western ideal is for a thin woman, some cultures prefer plumper women,[139][183] which has been argued to support that attraction for a particular BMI merely is a cultural artifact.[183] The attraction for a proportionate body also influences an appeal for erect posture.[184] One cross-cultural survey comparing body-mass preferences among 300 of the most thoroughly studied cultures in the world showed that 81% of cultures preferred a female body size that in English would be described as "plump".[185]

Availability of food influences which female body size is attractive which may have evolutionary reasons. Societies with food scarcities prefer larger female body size than societies that have plenty of food. In Western society males who are hungry prefer a larger female body size than they do when not hungry.[186]

BMI has been criticised for conflating fat and muscle, and more recent studies have concentrated on body composition. Among Australian university students, the most attractive body composition for women (10.31 kg fat, 42.45 kg muscle) was found to be lower in fat than both the most healthy appearing composition, and below the healthy range.[96]

In the United States, women overestimate men's preferences for thinness in a mate. In one study, American women were asked to choose what their ideal build was and what they thought the build most attractive to men was. Women chose slimmer than average figures for both choices. When American men were independently asked to choose the female build most attractive to them, the men chose figures of average build. This indicates that women may be misled as to how thin men prefer women to be.[183] Some speculate that thinness as a beauty standard is one way in which women judge each other[145] and that thinness is viewed as prestigious for within-gender evaluations of other women. A reporter surmised that thinness is prized among women as a "sign of independence, strength and achievement."[145] Some implicated the fashion industry for the promulgation of the notion of thinness as attractive.[187]

East Asians have historically preferred women whose bodies had small features. For example, during the Spring and Autumn period of Chinese history, women in Chinese harems wanted to have a thin body in order to be attractive for the Chinese emperor. Later, during the Tang Dynasty, a less thin body type was seen as most attractive for Chinese women.[188] In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to be slender like a "cane" or a "twig".[133] In the Chinese text Jeweled Chamber Secrets (Chinese: 玉房秘訣) from the Six Dynasties period, the ideal woman was described as not being "large-boned".[135]

In the Victorian era, women who adhered to Victorian ideals were expected to limit their food consumption to attain the ideal slim figure.[189] In Middle English literature, "slender" women are considered beautiful.[60]

Measurement of waist hip ratio: In a lean person (left), the waist can be measured at its narrowest point, while for a person with convex waist (right), it may be measured at about one inch[190] above the navel. The hip is measured at its widest portion of the buttocks at left, and at the greater trochanters at right.

A WHR of 0.7 for women has been shown to correlate strongly with general health and fertility. Women within the 0.7 range have optimal levels of estrogen and are less susceptible to major diseases such as diabetes, heart disease, and ovarian cancers.[191] Women with high WHR (0.80 or higher) have significantly lower pregnancy rates than women with lower WHRs (0.70–0.79), independent of their BMIs.[192][193] Female waist-to-hip ratio (WHR) has been proposed by evolutionary psychologists to be an important component of human male mate choice, because this trait is thought to provide a reliable cue to a woman's reproductive value.[194]

Both men and women judge women with smaller waist-to-hip ratios more attractive.[195] Ethnic groups vary with regard to their ideal waist-to-hip ratio for women,[196] ranging from 0.6 in China,[197] to 0.8 or 0.9 in parts of South America and Africa,[198][199][200] and divergent preferences based on ethnicity, rather than nationality, have also been noted.[201][202] A study found the Machiguenga people, an isolated indigenous South American ethnic group, prefer women with high WHR (0.9).[203] The preference for heavier women, has been interpreted to belong to societies where there is no risk of obesity.[204]

In Chinese, the phrase "willow waist" (Chinese: 柳腰) is used to denote a beautiful woman by describing her waist as being slender like a willow branch.[135]

In the Victorian era, a small waist was considered the main trait of a beautiful woman.[189] The term "wasp waist" describes an extreme fashion silhouette, produced by a style of corset and girdle.

Most men tend to be taller than their female partners.[18] It has been found that, in Western societies, most men prefer shorter women. Having said this, height is a more important factor for a woman when choosing a man than it is for a man choosing a woman.[205] Men tend to view taller women as less attractive,[206] and people view heterosexual couples where the woman is taller to be less ideal.[206] Women who are 0.7 to 1.7 standard deviations below the mean female height have been reported to be the most reproductively successful,[207] since fewer tall women get married compared to shorter women.[206] However, in other ethnic groups, such as the Hadza, study has found that height is irrelevant in choosing a mate.[105]

In Middle English literature, 'tallness' is a characteristic of ideally beautiful women.[60]

This drawing of two female figures is a remake of the drawing of the leg-to-body ratio (LBR) extremes used in the experiment by Swami et al. (2006) to find out what LBR is considered the most attractive. The female figure with the lowest LBR and shortest legs at left had the lowest average attractiveness ratings whereas the figure with the highest LBR and longest legs at right had the highest average attractiveness ratings from both British men and women.[100]

A study using Polish participants by Sorokowski found 5% longer legs than average person leg to body ratio for both on man and woman was considered most attractive.[208] The study concluded this preference might stem from the influence of leggy runway models.[209] Another study using British and American participants, found "mid-ranging" leg-to-body ratios to be most ideal.[210]

A study by Swami et al. of British male and female undergraduates showed a preference for men with legs as long as the rest of their body and women with 40% longer legs than the rest of their body.[100] The researcher concluded that this preference might be influenced by American culture where long legged women are portrayed as more attractive.[100]

Marco Bertamini criticized the Swami et al. study for using a picture of the same person with digitally altered leg lengths which he felt would make the modified image appear unrealistic.[211] Bertamini also criticized the Swami study for only changing the leg length while keeping the arm length constant.[211] After accounting for these concerns in his own study, Bertamini's study which used stick figures also found a preference for women with proportionately longer legs than men.[211] When Bertamini investigated the issue of possible sexual dimorphism of leg length, he found two sources that indicated that men usually have slightly proportionately longer legs than women or that differences in leg length proportion may not exist between men and women.[211] Following this review of existing literature on the subject, he conducted his own calculations using data from 1774 men and 2208 women. Using this data, he similarly found that men usually have slightly proportionately longer legs than women or that differences in leg length proportion may not exist between men and women. These findings made him rule out the possibility that a preference for women with proportionately longer legs than men is due proportionately longer legs being a secondary sex characteristic of women.[211]

According to some studies, most men prefer women with small feet,[212][213] such as in ancient China where foot binding was practiced.[214]

In Jewish Rabbinic literature, the rabbis considered small feet to be the ideal type of feet for women.[134]

Men have been found to prefer long-haired women.[121][215][216] An evolutionary psychology explanation for this is that malnutrition and deficiencies in minerals and vitamins causes loss of hair or hair changes. Hair therefore indicates health and nutrition during the last 2–3 years. Lustrous hair is also often a cross-cultural preference.[170]

A component of the female beauty ideal in Persian literature is for women to have black hair,[132] which was also preferred in Arabian society in the Middle Ages.[133] In Middle English literature, curly hair is a necessary component of a beautiful woman.[60]

Evidence from various cultures suggests that heterosexual men tend to find the sight of women's genitalia to be sexually arousing.[217]

The way an individual moves can indicate health and even age and influence attractiveness.[170] A study reflecting the views of 700 individuals and that involved animated representations of people walking, found that the physical attractiveness of women increased by about 50 percent when they walked with a hip sway. Similarly, the perceived attractiveness of males doubled when they moved with a swagger in their shoulders.[218]

Les Deux Perles Fernand Le Quesne (The two pearls, 1889). This painting was intended to "contrast a Caucasian with an African beauty". In the painting, the black woman represents the beauty of a black pearl and the white woman represents the beauty of a white pearl.[219]

A preference for lighter-skinned women has been documented across many cultures.[220][221] A 2010 study found a preference for lighter-skinned women in New Zealand and California.[222] In parts of Africa and Asia, skin bleaching is common.[223] The universality of this preference however has been questioned by a 2006 study on men of the Bikosso tribe in Cameroon which found no consistent preference for either lighter or darker skinned women.[200] The relationship between attractiveness and skin colour may also intersect with ethnicity and prior experience.[224]

Skin color preferences may shift over time, as in Western culture, where tanned skin used to be associated with the sun-exposed manual labor of the lower-class, but since the mid-20th century it has generally been considered more attractive and healthier than before, with sun tanning becoming fashionable.[225][226][227][228][229]

Skin radiance or glowing skin may influence perception of beauty and physical attractiveness.[230][231]

More recent research has suggested that redder and yellower skin tones,[117] reflecting higher levels of oxygenated blood,[118] carotenoid and to a lesser extent melanin pigment,[119] and net dietary intakes of fruit and vegetables, appear healthier, and therefore more attractive.

There are some subtle changes in women's perceived attractiveness across the menstrual cycle. During their most fertile phase, we can observe some changes in women's behavior and physiology. A study conducted by G. Miller (2007) examined the amount of tip earnings by lap dancers across the menstrual cycle. He found that dancers received nearly US$15 more when they were near ovulation than during the rest of the month. This suggests that women either are more attractive during ovulation phase, or they experience a significant change in their behavior.[232] Some other studies have found that there are subtle differences in women's faces when in their fertile phase. Bobst and Lobmaier (2012) created 20 prototyped photographs, some of a female during ovulation and some during the luteal phase. Men were asked to choose the more attractive, the more caring and the more flirtatious faces. They found a significant preference for the follicular phase (ovulation). This suggests that subtle shape differences in faces occurring during the female's ovulation phase are sufficient to attract men more.[233] This idea is supported by another study, where a similar experiment was done. Men and women had to judge photographs of women's faces taken during their fertile phase. They were all rated more attractive than during non-fertile phase. They are some subtle visible cues to ovulation in women's faces, and they are perceived as more attractive, leading to the idea that it could be an adaptive mechanism to raise a female's mate value at that specific time (when probability of conception is at its highest).[232]

Women's attractiveness, as perceived by men and women, slightly differs across her menstrual cycle, being at peak when she is in her ovulation phase. Jones et al. (2008), focused on women's preferences for masculinity, apparent health and self-resemblance and found that it varies across the cycle. They explained 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 pregnancy.[234]

Similarly, female prefer the scent of symmetrical men and masculine faces during fertile phases as well as stereotypical male displays such as social presence, and direct intrasexual competitiveness.[235]

During the follicular phase (fertile), females prefer more male's traits (testosterone dependent traits such as face shape) than when in non-fertile phase. Those findings have been found in the voice, showing that females’ preferences for more masculine voices over feminine voices increase the fertile phase of the menstrual cycle.[236]

But not only females' preferences vary across cycle, their behaviours as well. Effectively, men respond differently to females when they are on ovulatory cycle,[232] because females act differently. Women in the ovulatory phase are flirtier with males showing genetic fitness markers than in low fertile phase.[237] It has been shown in some studies that women high in estrogen are generally perceived to be more attractive than women with low levels of estrogen, based on women not wearing make-up. High estrogen level women may also be viewed as healthier or to have a more feminine face.[238]

Similarly, a study investigated the capacity of women to select high quality males based on their facial attractiveness. They found that facial attractiveness correlated with semen quality (good, normal, or bad depending on sperm morphology and motility). The more attractive a man's face is, linked to his sperm being of better quality.[239]

Sexual ornaments are seen in many organisms; in humans, females have sexual ornamentation in the form of breasts and buttocks. The physical attraction to sexual ornaments is associated with gynoid fat, as opposed to android fat, which is considered unattractive.[240] In human females, proximate causes of the development of sexual ornaments are associated with the predominance of estrogen in puberty. The activation of estrogen receptors around the female skeletal tissue causes gynoid fat to be deposited in the breasts, buttocks, hips and thighs, producing an overall typical female body shape.[241] Specifically, female breasts are considered more attractive when symmetrical, rather than asymmetrical,[242] as this is thought to reflect good developmental stability.[243]

Sexual ornaments are considered attractive features as they are thought to indicate high mate value, fertility,[244] and the ability to provide good care to offspring. They are sexually selected traits present for the purpose of honest signalling and capturing the visual attention of the opposite sex, most commonly associated with females capturing the visual attention of males. It has been proposed that these ornaments have evolved in order to advertise personal quality and reproductive value.[245] Honest signalling with sexual ornaments is associated with ultimate causation of these evolved traits. The evolution of these ornaments is also associated with female-female competition in order to gain material benefits provided by resourceful and high status males.[36] In humans, once these sexual ornaments develop, they are permanent. It is thought that this is associated with the long-term pair bonding humans engage in; human females engage in extended sexual activity outside of their fertile period.[246] This relates to another ultimate cause of sexual ornaments with function in obtaining non-genetic material benefits from males. In other animal species, even other primate species, these advertisements of reproductive value are not permanent. Usually, it is the point at which the female is at her most fertile, she displays sexual swellings.[247]

Adolescence is the period of time whereby humans experience puberty, and experience anatomical changes to their bodies through the increase of sex hormones released in the body. Adolescent exaggeration is the period of time at which sexual ornaments are maximised, and peak gynoid fat content is reached.[36] In human females, the mean age for this is approximately 16 years. Female breasts develop at this stage not only to prepare for reproduction, but also due to competition with other females in displaying their reproductive value and quality to males.[36]