25. joulukuuta 2014

Poimintoja Evolutionary Psychology: The New Science of the Mind kirjasta

Olen alle keräillyt psykologian professorin David Buss:in kirjasta mielenkiintoisia kohtia, joissa varsinkin käsitellään kauneutta ja parinvalintaa. Kirjassa näyttäisi olevan paljonkin viittauksia vanhoihin tutkimuksiin, jonka takia olisi hyvä toistaa näitä tutkimuksia ja tehdä ne paremmin, mutta poimimalla alla olevista lainauksista hakusanoja Google Scholar:iin voi tietenkin katsoa, että löytyykö uusia tutkimuksia. Olen poiminut nämä lainaukset kirjan neljännestä painoksesta, jonka kyllä piraatti voi löytää netistä, mutta lähde linkin kautta pääsee lukemaan edellistä versiota kirjasta.

Our ancestors had access to two types of observable evidence of a woman’s reproductive value: (1) features of physical appearance, such as full lips, clear skin, smooth skin, clear eyes, lustrous hair, good muscle tone, and body fat distribution; and (2) features of behavior, such as a bouncy youthful gait, an animated facial expression, and a high energy level. These physical cues to youth and health, and hence to fertility and reproductive value, have been hypothesized to be some of the key components of male standards of female beauty (Symons, 1979, 1995) (see Figure 5).

Psychologists Clelland Ford and Frank Beach discovered several universal cues that correspond with the evolutionary theory of beauty (1951). Signs of youth, such as clear, smooth skin, and signs of health, such as an absence of sores and lesions, are universally regarded as attractive. Any cues to ill health or older age are seen as less attractive. Poor complexion is always considered unattractive. Ringworm, facial disfigurement, and filthiness are universally undesirable. Freedom from disease is universally attractive

Among the Trobriand Islanders in northwestern Melanesia, for example, anthropologist Bronislaw Malinowski reports that “sores, ulcers, and skin eruptions are naturally held to be specially repulsive from the viewpoint of erotic contact” (Malinowski, 1929, p. 244). The “essential conditions” for beauty, in contrast, are “health, strong growth of hair, sound teeth, and smooth skin.” Specific features, such as bright, shining eyes and full, well-shaped lips rather than thin or pinched lips, are especially important to the islanders.

Another cue to youth and health is the length and quality of women’s hair. One study interviewed 230 women at various public locations about their age, subjective health status, and relationship status, and obtained observer measures of hair length and hair quality (Hinsz, Matz, & Patience, 2001). Hair length and quality were strong cues to youth: Younger women had longer hair of higher-rated quality than did older women. Furthermore, observer’s judgments of women’s hair quality were positively correlated with women’s subjective judgments of their own health.

Studies confirm that skin quality is especially important in judgments of attractiveness. It provides a cue to a woman’s age and a partial record of her lifetime health (Sugiyama, 2005). Clear unblemished skin signals an absence of parasites, absence of skin-damaging diseases during development, and possibly “good genes” to withstand disease and heal without infection (Singh & Bronstad, 1997). Studies find that skin quality is indeed linked with perceived facial attractiveness (Fink & Neave, 2005). Female faces with skin that has a homogeneous skin color distribution, not splotchy, receive higher attractiveness ratings and are perceived to be younger (Fink, Grammer, & Matts, 2006; Fink et al., 2008). Furthermore, more skin blood color in female faces enhances the perception of healthiness, perhaps corresponding to the subjective impression that some faces seem to “glow” (Stephen et al., 2009). This may also explain why some women use rouge as makeup, since it enhances perceptions of health and vitality.

Facial femininity is another cue to attractiveness (Gangestad & Scheyd, 2005). Facial femininity includes cues such as full lips, relatively large eyes, thinner jaws, small chin, high cheekbones, and a relatively short distance between mouth and jaw. Female facial femininity is likely to be a marker of reproductive value for two reasons. First, as women age, their facial features become less feminine. Second, facial femininity is linked with higher levels of estrogen, the ovarian hormone that correlates with fertility (Schaefer et al., 2006). Meta-analyses reveal that facial femininity is one of the most powerful cues to women’s attractiveness (Rhodes, 2006). Feminine voices—relatively high pitched—are also found to be more attractive in women (Collins & Missing, 2003; Feinberg et al., 2005).

Facial symmetry is another correlate of female attractiveness (Gangestad & Scheyd, 2005; Rhodes, 2006). Symmetry is hypothesized to be a cue to developmental stability, a hypothesized sign of “good genes” and the capacity to withstand environmental insult. Symmetrical female faces are indeed judged to be healthier than less symmetrical faces (Fink et al., 2006). Facial symmetry is positively correlated with judgments of attractiveness, although the link is weaker than that of facial femininity (Rhodes, 2006).

Facial averageness is another quality linked with attractiveness, although this may seem counterintuitive. Researchers created computer composites of the human face, superimposing faces on each other to create new faces (Langlois & Roggman, 1990). The new faces differed in the number of individual faces that made them up—four, eight, sixteen, or thirty-two. The composite faces—the averages of the individual faces—were judged more attractive than the individual faces. And the more faces that went into the composite, the more attractive the face was judged to be. Two competing hypotheses have been advanced to explain why average faces are attractive. First, people may show a generalized cognitive preference for things that are easily processed, and stimuli that match an average prototype may be easier to process. People do indeed find averaged images of fish, birds, and even cars more attractive than individual fish, birds, or cars (Rhodes, 2006). Second, averageness may be a marker of genetic or phenotypic quality (Gangestad & Scheyd, 2005). Deviations from averageness may be cues to environmental insults such as disease or genetic mutations.

Leg length, especially long legs relative to torso length, has been hypothesized to be a cue to health and biomechanical efficiency (Sorokowski & Pawlowski, 2008). Using silhouette stimuli that held overall height constant, but varied leg length, researchers discovered that legs roughly 5 percent longer than average are viewed as maximally attractive in women (Sorokowski & Pawlowski, 2008). Other studies confirm that both sexes view relatively longer legs as more attractive in women (Bertamini & Bennett, 2009; Swami, Einon, & Furnham, 2006). Perhaps this explains why some women wear high-heeled shoes—they make legs appear to be relatively longer. Interestingly, a study of 9,998 Chinese found that women with longer legs had more offspring, an association especially strong in women from lower socioeconomic backgrounds (Fielding et al., 2008).
Standards of Beauty Emerge Early in Life. Most traditional psychological theories of attraction have assumed that standards of attractiveness are learned gradually through cultural transmission and therefore do not emerge clearly until a child is three or four years old or even later (Berscheid & Walster, 1974; Langlois et al., 1987). However, psychologist Judith Langlois and her colleagues have overturned this conventional wisdom by studying infants’ social responses to faces (Langlois, Roggman, & Reiser-Danner, 1990).

Adults evaluated color slides of White and Black female faces for their attractiveness. Then infants two to three months and six to eight months old were shown pairs of these faces that differed in degree of attractiveness. Both younger and older infants gazed longer at the more attractive faces, suggesting that standards of beauty apparently emerge quite early in life. In a second study, they found that twelve-month-old infants played significantly longer with facially attractive dolls than with unattractive dolls. This evidence challenges the commonly held view that the standards of attractiveness are learned through gradual exposure to current cultural models. No training seems necessary for these standards to emerge.
Standards of Beauty Are Consistent across Cultures. The constituents of beauty are neither arbitrary nor culture bound. When psychologist Michael Cunningham asked people of different races to judge the facial attractiveness of Asian, Hispanic, Black, and White women in photographs, he found tremendous consensus about who is and who is not considered goodlooking (Cunningham et al., 1995). The average correlation between racial groups in their ratings of the attractiveness of these photographs was .93. In a second study by the same investigators, Taiwanese subjects agreed with the other groups in the average ratings of attractiveness (r .91). Degree of exposure to Western media did not affect the judgments of attractiveness in either study. In a third study, Blacks and Whites showed tremendous agreement about which women’s faces were most and least attractive (r .94). Consensus has also been found among Chinese, Indian, and English subjects; between South Africans and North Americans; between Black and White Americans; and between Russians, Ache Indians, and Americans (Cross & Cross, 1971; Jackson, 1992; Jones, 1996; Morse, Gruzen, & Reis, 1976; Thakerar & Iwawaki, 1979).
Beauty and the Brain. Evolutionary psychologists are beginning to use neuroscience technology to identify the links between psychological mechanisms and specific brain circuits. Exploiting the new technology of functional magnetic resonance imaging (fMRI), scientists Itzhak Aharon, Nancy Etcoff, and their colleagues sought to identify the “reward value” of different images (Aharon et al., 2001). They exposed heterosexual male participants to four sets of faces differing in attractiveness, as determined by prior ratings: attractive females, average females, attractive males, and average males. While participants viewed these images, their brains were neuroimaged in six regions. The results proved to be dramatic. When men looked at attractive female faces, the nucleus accumbens area of the brain became especially activated. The nucleus accumbens is known to be fundamental reward circuitry—that is, it is a well-documented pleasure center of the brain. This reward circuit of the brain fails to become activated when men look at either typical female faces or any of the male faces. Beautiful female faces, in short, are especially rewarding to men, psychologically and neurologically. This important finding takes the field a step closer to identifying the specific neurological bases of mating adaptations that have been well documented psychologically and behaviorally.
Facial beauty is only part of the picture. Features of the rest of the body may also provide cues to a woman’s reproductive capacity. Standards for female bodily attractiveness vary somewhat from culture to culture. The most culturally variable standard of beauty seems to be in the preference for a slim versus a plump body build, and it is linked with the social status that build conveys. In cultures where food is scarce, such as among the Bushmen of Australia, plumpness signals wealth, health, and adequate nutrition during development (Rosenblatt, 1974). Indeed, there is powerful evidence that in ecologies where food shortages are common, such as in Kenya, Uganda, and certain parts of Equador, men prefer women who are heavier and possess more body fat (Sugiyama, 2005). Even within cultures, men prefer heavier women when there are economic hard times (Pettijohn & Jungeberg, 2004), when they are hungry (Pettijohn, Sacco, & Yerkes, 2009), and when they feel poor (Nelson & Morrison, 2005). In cultures where food is relatively abundant, such as the United States and many Western European countries, the relationship between plumpness and status is reversed, and the wealthy distinguish themselves by being thin (Symons, 1979). Thus, although “body-weight preference varies across cultures and time, it does so in predictable ways” (Sugiyama, 2005, p. 318), suggesting context-dependent adaptations.

One study revealed a disturbing aspect of U.S. women’s and men’s perceptions of the desirability of plump or thin body types (Rozin & Fallon, 1988). Men and women viewed nine female figures that varied from very thin to very plump. The women were asked to indicate their ideal for themselves, as well as their perception of what men’s ideal female figure was. In both cases, women selected a figure that was slimmer than average. When men were asked to select which female figure they preferred, however, they selected the figure of exactly average body size. So U.S. women think that men want them to be thinner than is in fact the case. A study of 7,434 individuals from twenty-six cultures in ten world regions found the same pattern—men consistently prefer female bodies that are heavier in weight than women’s perceptions of what men prefer (Swami et al., 2010).

Psychologist Devendra Singh has discovered one preference for body shape that may be universal: the preference for a particular ratio between the size of a woman’s waist and the size of her hips (Singh, 1993; Singh & Young, 1995). Before puberty, boys and girls show similar fat distributions. At puberty, however, a dramatic change occurs. Men lose fat from their buttocks and thighs, whereas the release of estrogen in pubertal girls causes them to deposit fat in the lower trunk, primarily on their hips and upper thighs. Indeed, the volume of body fat in this region is 40 percent greater for women than for men.

The waist-to-hip ratio (WHR) is thus similar for the sexes before puberty, in the range of .85 to .95. After puberty, however, women’s hip fat deposits cause their WHRs to become significantly lower than men’s. Healthy, reproductively capable women have WHRs between 67 and .80, whereas healthy men have a ratio in the range of .85 to .95. Abundant evidence now shows that the WHR is an accurate indicator of women’s reproductive status. Women with lower ratios show earlier pubertal endocrine activity. Married women with higher ratios have more difficulty becoming pregnant, and those who do get pregnant do so at a later age than women with lower ratios. The WHR is also an accurate indication of long-term health status. Diseases such as diabetes, hypertension, heart attack, stroke, and gallbladder disorders have been shown to be linked with the distribution of fat, as reflected by the ratio, rather than with the total amount of fat per se. One study found that women with a low WHR (as indicated by small waist) and relatively large breasts, compared to women from three groups with different combinations of bodyshape variables, had 26 percent higher levels of the ovarian hormone oestradiol (E2), which is a good predictor of fertility and pregnancy success (Jasienska et al., 2004). The link between the WHR and both health and reproductive status makes it a reliable cue for ancestral men’s preferences in a mate.

Singh discovered that WHR is indeed a powerful part of women’s attractiveness. In a dozen studies conducted by Singh, men rated the attractiveness of female figures that varied in both WHR and total amount of fat. Again, men found the average figure to be more attractive than either a thin or a fat figure. Regardless of the total amount of fat, however, men find women with low WHRs the most attractive. Women with a WHR of 0.70 are seen as more attractive than women with a WHR of 0.80, who in turn are seen as more attractive than women with a WHR of 0.90. Studies with line drawings and with computer-generated photographic images produced the same results. The bodies of women who underwent surgery to remove fat from their stomachs and implant it on their buttocks—creating a lower WHR—were judged more attractive post-operation (Singh & Randall, 2007). Singh’s analysis of Playboy centerfolds and winners of U.S. beauty contests over the past thirty years confirmed the invariance of this cue. Although both centerfolds and beauty contest winners got slightly thinner over that period, their WHRs remained the same, roughly 0.70.

A preference for a relatively low WHR has also been found in the United Kingdom, Australia, Germany, India, and Guinea-Brissan (Africa) and on the Azore Islands (Connolly, Mealey, & Slaughter, 2000; Furnham, Tan, & McManus, 1997; Singh, 2000).

A cross-cultural study of female “escorts” advertised online found that the average values of the stated WHRs, as calculated from reported body measurements of waist and hips, were .70, .75, .71, .76, and .69 in Europe, Oceania, Asia, North America, and Latin America, respectively (Saad, 2008). Another study found that men who were blind from birth, when assessing female body shape through touch, prefer the low WHR mannequin models, suggesting that the preference for low WHR can develop with the total absence of visual input (Karremans, Frankenhuis, & Arons, 2010). Finally, an eye-tracking study discovered that initial visual fixations occurred most often for female waists and breasts, and that men rated women with a low WHR as most attractive, regardless of breast size (Dixon et al., 2010).
Advertisers exploit the universal appeal of beautiful, youthful women. Madison Avenue is sometimes charged with advancing a single arbitrary standard of beauty that everyone else must live up to. This accusation is at least partially false. The standards of beauty, as we have seen, are not arbitrary but rather embody reliable cues to fertility and reproductive value. Advertisers that more closely exploit existing mate preferences are almost sure to be more successful than those that do not. Advertisers perch a clear-skinned, regular-featured young woman on the hood of the latest car because the image exploits men’s evolved psychological mechanisms and therefore sells cars.

In one study, Buss (1988c) examined the self-reported usage and the perceived effectiveness of 101 tactics of mate attraction. Appearance enhancement figured prominently. Women, significantly more than men, reported using the following attraction tactics: “I wore facial makeup,” “I went on a diet to improve my figure,” “I learned how to apply cosmetics,” “In kept myself well-groomed,” “I used makeup that accentuated my looks,” and “I got a new and interesting hair style.” The ratings of perceived effectiveness matched the self-reported performance: All acts of appearance enhancement were judged to be more effective for women in attracting men than vice versa.

William Tooke and Lori Camire (1991) looked at the usage and effectiveness of tactics of intersexual deception, or the ways in which men deceive women and women deceive men in the mating arena. They asked male and female undergraduates to report on their performances and rate the effectiveness of various tactics of deceiving the opposite sex. Women, more than men, used tactics of deception involving their physical appearance: “I sucked in my stomach when around members of the opposite sex,” “I wore a hairpiece around members of the opposite sex,” “I wore colored contact lenses to make my eyes appear to be a different color,” “I dyed my hair,” “I wore false fingernails,” “I wore dark clothing to appear thinner than I really was,” and “I wore padded clothing.” Women’s use of deceptive appearance enhancement was judged to be significantly more effective in attracting mates than men’s use of such tactics. Another study found that as women get older, they tend to withhold information about their age when they place personal advertisements for mates (Pawlowski & Dunbar, 1999b). In sum, when it comes to attracting the opposite sex, women’s behavior appears to be highly responsive to the preferences expressed by men.

Women also appear to be sensitive to the mate preferences of men in their interactions involving rivals (Buss & Dedden, 1990). One tactic involved derogating a rival’s physical appearance using acts such as “made fun of his/her appearance,” “told others that the rival was fat and ugly,” and “made fun of the size and shape of the rival’s body.” Derogating a rival’s physical appearance was judged to be more effective when women used it than when men used it. Interestingly, Maryanne Fisher found that women in the high estrogen (fertile) phase of their cycle are more likely than women in the low estrogen phase to derogate a rival’s physical appearance (Fisher, 2004). She concludes: “If women compete intrasexually for ‘good’ mates via attractiveness, it would be advantageous to have heightened levels of competition when it matters most—during times critical for reproduction” (Fisher, 2004, p. S285).

Successful long-term mating requires sustained cooperative alliances over time. Similarity leads to emotional bonding, cooperation, communication, mating happiness, lower risk of breaking up, and possibly increased survival of children (Buss, 2003). Women and men alike show strong preferences for mates who share their values, political orientations, worldviews, intellectual level, and to a lesser extent their personality characteristics. The preference for similarity translates into actual mating decisions, a phenomenon known as homogamy—people who are similar on these characteristics date (Wilson, Cousins, & Fink, 2006) and get married (Buss, 1985) more often than those who are dissimilar. Homogamy for physical appearance might be due to “sexual imprinting” on the opposite-sex parent during childhood (Bereczkei, Gyuris, & Weisfeld, 2004). Interestingly, daughters who received more emotional support from their fathers were more likely to choose similar-looking mates. Finally, there is strong homogamy for overall “mate value,” with the “10s” mating with other “10s” and the “6s” mating with other “6s” (Buss, 2003).

Who Are Newborn Babies Said to Resemble? Daly and Wilson (1982) suggested that mothers should be motivated to promote a putative father’s certainty of paternity by remarking on the newborn’s similarity in appearance to him. Success in promoting the man’s belief that he is the father should increase his willingness to invest in that child. To examine these efforts by mothers, Daly and Wilson secured videotapes of 111 U.S. births that. ranged in duration from five to forty-five minutes. The verbal utterances were recorded verbatim for subsequent scoring. Of the 111 videotapes, 68 contained explicit references to the baby’s appearance.

By chance alone, one would expect babies to be said to resemble the mother 50 percent of the time and the father 50 percent of the time. In fact, when the baby was said to resemble either parent, the mother’s remarks about the resemblance to the father were four times as frequent (80 percent) as her remarks about the baby’s resemblance to her (20 percent). Sample remarks by mothers included “It looks like you” (one woman said this three times to her husband), “feels like you,” “just like daddy,” “he looks like you, got a head of hair like yours,” and “he looks like you, honestly he does” (Daly & Wilson, 1982, p. 70).


An intriguing study suggests that perceptions of resemblance might affect men’s subsequent investment in the child. Using a computerized “morphing” procedure, the experimenters created photographs of children into which either participants’ faces were morphed or those of other people were morphed (Platek et al., 2002). After viewing each photograph, participants completed a questionnaire that asked about how much they would hypothetically invest in each of the children. Men found the faces into which their photo had been morphed to be the most attractive and indicated that they would spend more time with this child, invest more money in this child, and be least resentful of paying child support to this child. In contrast, women were much less affected by the child’s resemblance to themselves.

Research using fMRI (functional magnetic resonance imaging) brain-scan technology has discovered that men show greater cortical activity than do women when shown images of children’s faces that resemble their own (Platek, Keenan, & Mohamed, 2005). Specifically, they show higher levels of neural activation in the left front cortex, an area of the brain linked with inhibiting negative responses (Platek et al., 2004). These studies point to progress in identifying the underlying specific brain mechanisms underlying evolved psychological adaptations (Platek, Keenan, & Shackelford, 2007).