Why Women Have Sex. C. Meston and D. Buss. A Puke (TM) Audiobook

Why Women Have Sex.
Understanding Sexual Motivations, from Adventure to Revenge, and Everything in Between.
DOCTOR CINDY MESTON.
AND DOCTOR DAVID BUSS.
Formatted for Machine speech, 2023
First Edition 2009.

"...we identified 237 distinct sexual motivations"

Inside the Sexual Mind.
Why women have sex is an extraordinarily important but surprisingly little-studied topic. One reason for its neglect is that scientists and everyone else have assumed that the answers are already obvious, to experience pleasure, to express love, or, at the very heart of the biological drive to have sex, to reproduce. So, more than five years ago, we decided to undertake an intensive research project, involving more than three thousand individuals, to uncover the mysteries of women’s sexuality.
When our scientific article “Why Humans Have Sex” was published in the August 2007 issue of Archives of Sexual Behavior, it generated an avalanche of interest. What that media coverage revealed, however, was just the tip of the iceberg. In that original study, we identified 237 distinct sexual motivations that covered an astonishing variety of psychological nuance. These motives ranged from the mundane, “I was bored”, to the spiritual, “I wanted to get closer to God”, from altruistic, “I wanted my man to feel good about himself”, to vengeful, “I wanted to punish my husband for cheating on me”. Some women have sex to feel powerful, others to debase themselves. Some want to impress their friends. Others want to harm their enemies, “I wanted to break up a rival’s relationship by having sex with her boyfriend”. Some express romantic love, “I wanted to become one with another person”. Others express disturbing hate, “I wanted to give someone else a sexually transmitted disease”. But none of these reasons conveyed the “why” that hid behind each motive.
Through statistical procedures, we clustered the motivations into natural groupings. We then set out to explore women’s sex lives in richer detail in a new study designed specifically for this book. And we integrated our research with all the latest scientific findings, from our labs and from the labs of other scientists throughout the world, to present what we believe is one of the richest and deepest understandings of women’s sexuality yet achieved.
Why Women Have Sex brings these insights to life with detailed descriptions of women’s actual sexual encounters, the motives that impel women to have sex, and the theory behind why each of those motives exists in women’s sexual psychology. Although human sexuality has been the primary focus of our scientific research for many years, this project proved to be more illuminating about women’s sexuality than we ever expected.
How did we end up collaborating on this extraordinary project? As it happens, we have offices right next door to each other in the psychology department at the University of Texas at Austin, where we are both professors. Given our shared professional interests, we’ve had many conversations about human sexuality. The topic of conversation turned one day to sexual motivation, and we started discussing a simple question: Why do people have sex?
As coauthors, we combine uniquely complementary domains of expertise. One of us, Cindy M Meston, is a clinical psychologist and one of the world’s leading experts on the psychophysiology of women’s sexuality. The other, David M Buss, is an evolutionary psychologist and one of the world’s scientific experts on strategies of human mating. Our collaboration allowed us to develop a deeper understanding of women’s sexuality than either of us could have achieved working alone.
Viewed from both clinical and evolutionary perspectives, women’s sexuality poses interesting questions. Why do women desire some qualities in a mate, yet are repulsed by others? What tactics do women use to attract their preferred sex partners? Why do some women fuse love and sex psychologically? Why are erotic romance novels so much more appealing to women than to men? Why do some women have sex to keep a mate, whereas other women use sex to get rid of an unwanted mate?
The scientific study of sex, or “sexology,” is a multifaceted field spanning the disciplines of psychology, sociology, anthropology, evolutionary biology, and medicine. For the past several decades, sexology has focused on three core issues.
Defining and understanding what sexual behaviors, attitudes, and relationships are normal or healthy. Ascertaining how biological factors, life events, and personal preferences or circumstances shape our sexual identities and desires.
And discovering how human sexuality affects, and is affected by, social relationships. Clinical psychologists are especially interested in the extent to which a person’s sexual choices and responses can be modified or improved. Evolutionary psychologists study adaptive functions of the components of human sexual psychology, as well as why sexual motivations sometimes malfunction in the modern environment.
Since the late nineteenth century, sex researchers have primarily used three scientific methodologies for investigating human sexual behavior: case studies, questionnaires and surveys, and behavioral observation and assessment. The case study method involves careful, in-depth description of individuals with sexual problems or anomalies. For example, early sexologist Richard von Krafft-Ebing (1840 to 1902) observed a high prevalence of masturbation among his patients, which led him to conclude (erroneously) that masturbation was the source of all sexual variation. Based on case studies, psychologist Sigmund Freud (1856 to 1939) theorized that childhood erotic drives shaped adult sexual behavior.
The forerunner of survey research was Havelock Ellis (1859 to 1939), who emphasized the vast individual diversity in sexual behavior, and wrote a memoir detailing his “open marriage” to a self-identified lesbian. In the nineteen forties and fifties, Alfred Kinsey (1894 to 1956) and his collaborators Wardell B. Pomeroy, Paul H Gebhard, and Clyde E Martin redefined the way Americans viewed their sex lives with the publication of two reports describing the sexual activities of men and women. Kinsey and his team fashioned a standardized interview that they used to gather the detailed sex histories of approximately 18,000 men and women across the United States, the largest survey ever of human sexual practices.
Kinsey personally recorded 7,985 of the histories.
Robert Latou Dickinson (1861 to 1950), a practicing gynecologist in New York, pioneered the laboratory observation of women’s sexuality with his development of a glass observation tube to view and document women’s internal sexual anatomy. Kinsey also used direct observational techniques to study sexual response, but the current era of laboratory sex research began with the work of William H Masters (1915 to 2001) and Virginia E Johnson, who were married from 1971 until 1992. In contrast to the limited observations made by their predecessors, Masters and Johnson recruited nearly seven hundred men and women to participate in studies at their lab, where they documented the physiological changes that occur with sexual arousal and orgasm. They uncovered the role of vaginal lubrication in sexual arousal, the physiology of multiple orgasms, and the similarity between vaginal and clitoral orgasms in women.
Since the publication in 1966 of Masters and Johnson’s landmark book The Human Sexual Response, a relatively distinct branch of lab research has emerged: sexual psychophysiology. Studies in sexual psychophysiology investigate the complex interplay between the psychological (feelings, emotions and thought processes) and the physiological (hormones, brain chemicals, genital engorgement, and lubrication) in human sexual behavior.
Psychological sexual arousal is typically measured using questionnaires that ask how “turned on” or “turned off” a person feels in a certain context and whether his or her mood is positive, negative, relaxed, or anxious. In the early days of sexual psychophysiology, researchers interested in measuring human physiological arousal with adapted devices used in other species. For instance, penile erection monitors for men can be traced to machines used by horse breeders in the late nineteenth century to prevent masturbation in stud horses! In the early 1970s, two doctors developed a probe that could be used to measure thermal conductance in sheep vaginas. They claimed the device “caused no discomfort for the waking sheep” during the experiments, which lasted up to four hours.
Although the device proved too cumbersome and invasive for use in women, its design is not terribly different from modern vaginal probes.
Today, researchers measure physiological sexual responses, particularly genital blood flow, using a number of techniques.
In women, studies involve vaginal photoplethysmography (a light-sensing device), pulsed wave Doppler ultrasonography,pelvic magnetic resonance imaging, sensors that measure changes in the temperature of the vagina or labia, and thermal imaging of thighs and genitals. In addition, sexual psychophysiologists often record changes in heart rate, respiration rate, body temperature, blood pressure, and sweat gland activity. While these nongenital measures can provide information about a person’s physiological state during sexual arousal, they do not specifically indicate sexual response, since emotions such as anger, fear, anxiety, and even laughter can also trigger these changes. More recently, researchers have turned to functional magnetic resonance imaging (fMRI) to identify the areas of the brain involved in human sexual response and behavior.
All of these contemporary techniques allow researchers at the Meston Sexual Psychophysiology Lab and similar labs around the world to study the full spectrum of sexual response.
Over the past eleven years, the Meston Lab has investigated questions such as: What is the relation between levels of genital arousal and feeling psychologically aroused? How do early traumatic sexual experiences impact a woman’s ability to become aroused physically and mentally in adulthood? How does a woman’s body image impact her overall sexual function and satisfaction? What is the impact of cigarette smoking and other drugs on men’s and women’s ability to become sexually aroused? How do antidepressants impair women’s ability to become aroused and have an orgasm and how can we overcome these sexual side effects? Does the act of having sexual intercourse alter sex hormones in a way that can impact a woman’s overall sex drive? And why does anxiety sometimes increase and sometimes decrease women’s sexual functioning?
Psychological and physiological methods are also used to test evolution-based hypotheses about women’s sexual psychology. To some, it may seem odd to consider these questions through the lens of evolved sexual desires, evolved mate preferences, and an evolved psychology of sexual competition. Indeed, in the field of biology proper, until the Nineteen fifties it was viewed as unrespectable to speak of evolutionary processes having sculpted “behavior” at all, with proper biologists sticking closely to anatomy and physiology. The science of evolutionary biology has changed radically since then. The sexual organs, after all, are designed for sexual behavior! Anatomy, physiology, and psychology cannot be divorced from the behavior they were designed to produce.
Many people, when they think about evolution, draw up images such as “nature red in tooth and claw” and “survival of the fittest.” Although competition for survival is certainly part of evolutionary theory, in fact it is not the most important part.
Indeed, Darwin himself was deeply troubled by phenomena that could not be explained by this so-called “survival selection.” Marvels such as the brilliant plumage of peacocks, for example, simply defied explanation by survival selection.
How could this dazzling plumage possibly have evolved, since it is energetically costly and an open advertisement to predators, qualities clearly detrimental to survival? Darwin wrote in his private correspondence that the sight of a peacock gave him nightmares, since it defied the logic of his theory of natural selection.
Darwin’s nightmares subsided when he arrived at a second evolutionary theory that turns out to be central to the understanding of women’s sexual psychology: the theory of sexual selection. Sexual selection deals with the evolution of characteristics not because of the survival advantage they afford organisms, but rather because of mating advantage.
Sexual selection operates through two distinct processes, same-sex or intra-sexual competition and preferential mate choice, also called intersexual selection. In intra-sexual competition, members of one sex compete with one another, and the victors gain sexual access to the mates of their choice.
Two stags locking horns in combat is the stereotypical image of intra-sexual competition. Although Darwin stressed male-male competition, when it comes to humans, female-female competition is equally intense. Since males of every species differ in qualities such as physical attractiveness, health status, resource acquisition ability, and genetic quality, females who succeed in outcompeting other females for sexual access to males with beneficial qualities have a reproductive advantage over other females. And the evolutionary process is ultimately not about differential survival success, but differential reproductive success.
In intra-sexual competition the qualities that lead to access to more desirable mates get passed on in greater numbers because the victors mate more successfully and produce more or higher quality offspring. The characteristics that commonly lead to loss in these competitions bite the evolutionary dust, since they are passed on in fewer offspring. Although this process is sometimes easier to see in males, for whom competition is often ostentatious, the same logic applies to females, for whom competition is generally more subtle.
Among humans, for example, social reputation is a key component of same-sex competition. Social reputation is often gained or lost through subtle verbal signals, gossip, alliance formation, and other tactics that sometimes fly under the radar.
Evolution, which simply means change over time, occurs as a consequence of same-sex competition because the victors have greater access to desirable sex partners.
Preferential mate choice, on the other hand, involves desiring qualities in a mate that ultimately lead to greater reproductive success for the chooser. Women who choose to have sex with healthy men, for example, gain reproductive advantages over women who choose to have sex with disease ridden men. Women remain healthier themselves, since they do not pick up the man’s communicable diseases. Their children remain healthier, since they too avoid picking up the man’s diseases through close contact. And if the qualities linked to health are partly heritable, as we now know they are, then the women’s children will inherit genes for good health.
Women’s mating desires and the qualities they find sexually attractive have evolved because they led ancestral mothers to make wise choices, both in sex partners and in long-term mates.
Evolved psychological mechanisms go far beyond reproduction to include women’s sexual desires, patterns of sexual attraction, mate preferences, the emergence of the emotion of love, sexual jealousy, and much more. Each major component of women’s sexual psychology solves an adaptive problem, providing a specific benefit to women, or more precisely, provided a benefit to ancestral women that modern women have inherited. So when evolutionary psychologists use phrases such as “evolved psychological mechanisms” or “psychological adaptations,” they do not mean rigid, robotlike instincts expressed in behavior regardless of circumstances.
Rather, human psychological adaptations are extremely flexible, highly sensitive to circumstance, and activated only in some social contexts. An evolved emotion such as sexual jealousy, for example, might motivate a woman to have sex with her partner to keep his mind off other women. But a woman usually experiences sexual jealousy only if there is a sexual threat to her relationship.
Moreover, a woman might deal with a sexual threat in a multitude of other ways, such as increased vigilance or an increased outpouring of love. Even when women’s sexual adaptations are activated, it does not mean that they must invariably act on them. A woman’s sexual desire, for instance, might be activated by a chance encounter with a tall, dark, and handsome stranger, but she may choose not to act on that evolved desire due to a wish to remain loyal to her regular partner, a concern about damage to her reputation, or moral or religious convictions. Psychological adaptations are not inflexible instincts that ineluctably get expressed in behavior, but rather are flexible mechanisms whose expression is highly contingent on context.
Over the past twenty years, the Buss Evolutionary Psychology Lab has used a variety of research methods to explore human sexual psychology. The methods range from observational studies of women’s tactics of sexual attraction in singles bars to physiological recordings to imagining a romantic partner having sexual intercourse with someone else.
They include self-reports of sexual mate poaching, experimental studies of women’s sexual attraction to aspects of men’s physique, and hormonal assays of the effects of ovulation on women’s sexual desire. Samples include college undergraduates, dating couples, newlywed couples, older couples, and a culturally diverse sample of more than ten thousand individuals from thirty-three countries worldwide.
The Buss Lab has studied the dangerous passion of sexual jealousy, why women have affairs, parental tactics to constrain the sexuality of their daughters, the evolution of love, sexual deception, the effects of ovulation on women’s sexuality, whether men and women can be “just friends,” personality predictors of sexual satisfaction, cues that foretell a partner’s affair, derogation and gossip about sexual competitors, and “sexual intelligence.”
The notion that many components of women’s sexual psychology have an evolutionary function does not imply that all features are adaptive, or that every woman’s sexual behavior serves a benefit. Quite the contrary. As we will see throughout this book, some reasons that propel women into sexual encounters are self-destructive and cause personal problems, the loss of self-esteem, and even life tragedies.
Some reach clinical proportions and develop into distressing sexual disorders. We cover the entire range of women’s sexual psychology, from the lows of sexual disorders and how they can be treated to the highs of attaining and maintaining a fulfilling sexual life.
Our new and never-before-reported study of why women have sex was conducted online between June 2006 and April 2009. Web links and online classified advertisements requested women’s participation in a study designed to understand sexual motivations. The survey itself was hosted by a database using 128-bit encryption technology to protect the information from hackers and to ensure the utmost anonymity to the study’s participants. The women who participated first completed an informed consent during which they received full disclosure of the survey’s subject matter and were assured that they could discontinue the survey at any time. We have shared the women’s exact words, after eliminating any details that might identify them to maintain the confidentiality of their responses. We also let the participants know that if they had any concerns about the study or became distressed after answering the questions or sharing their stories, a clinical psychologist would be available to discuss their concerns with them.
The survey began by asking the women if they had ever had sex for one of the 237 reasons we identified in our original study. If a woman’s answer was yes, she would then be prompted to describe a specific experience, if no, she was asked about another reason for having sex. The women’s answers confirmed, enhanced, and enriched the quantitative findings of our initial investigation of why humans have sex.
Most important, they gave real women an opportunity to explain in their own words their motivations for having sex, providing a depth of insight into sexual psychology beyond what could be captured from statistical analysis.
In the course of the study, 1,006 women from a variety of backgrounds shared their experiences with us. They hailed from forty-six of the fifty states (all except Alaska, Montana, Nebraska, and Delaware), eight of the ten provinces of Canada (all but Saskatchewan and Prince Edward Island) and one of the two territories (Northwest Territory), three European countries (Germany, Belgium, and France), and Australia, New Zealand, Israel, and China. The women ranged in age from eighteen (the youngest we accepted into the study) to eighty-six and identified ethnically as American Indian, Asian, black, white (non-Hispanic), and Latino. About 57 percent considered themselves to be part of a specific religious tradition, Christian (Anglican, Baptist, Catholic, Episcopalian, Lutheran, Methodist, Mormon, Pentecostal, Protestant, and Seventh Day Adventists), Jewish, Muslim, Buddhist, Hindu, Taoist, Unitarian Universalist, and pagan or Wicca, while 26 percent said they were agnostics and 14 percent said they were atheists. Though the survey was conducted through the Internet, the participants came from diverse socioeconomic situations: 17 percent reported a family income of $25,000 or less a year, 31 percent an income between $25,001 and $50,000, 33 percent an income between $50,001 and $100,000, and 19 percent an income of more than $100,000.
Of course, we also asked the women about their relationship status and sexual orientation. Approximately 80 percent reported being in a relationship at the time, whereas 10 percent were currently dating but were not in a long-term relationship.
Ninety-three percent of the women said they were predominantly or exclusively heterosexual, with 2 percent identifying as bisexual and 5 percent identifying as predominantly or exclusively homosexual. Eleven percent actually did not choose one of these labels, opting for “other”, including gay, lesbian, asexual, bi-curious, heteroflexible, omnisexual, pansexual, queer, straight-plus, fluid, open, polyamorous, still questioning, and various combinations such as “mostly heterosexual plus a touch of gay.”
One of the surprises in our study was that for each reason that impels a woman to have sex, we discovered both successes and failures. Sex was often incredibly pleasurable, giving women a sense of excitement, love, connection, and self-exploration:
I have found, two things are important, being able to be really intense sexually with the person, while simultaneously being able to laugh heartily and really enjoy the experience of being with the person in a different way. It’s almost like the laughter and the sex satisfy two basic human urges simultaneously, heterosexual woman, age 42.
Women enjoy their sexiness and their sexuality.
But goals sought through sex are sometimes not reached.
Indeed, sex sometimes leaves women feeling lonely, bitter, and regretful. One woman in our study sought sex in order to relieve her loneliness and feelings of being unattractive, but it didn’t work out that way:
I had sex in my last relationship so I would not feel so damned lonely and unlovable. It was a stupid thing because it ended up worsening the feelings for me. I regret it now because we didn’t really know each other very well and were not really sure where we were going.
We split up after another month, heterosexual woman, age 39.
For every failure, however, we discovered sexual encounters of great success and true poignancy. Here is how one woman described sex as a way of boosting her self confidence:
I had sex with a couple of guys because I felt sorry for them. These guys were virgins and I felt bad that they had never had sex before so I had sex with them. I felt like I was doing them a big favor that no one else had ever done. I felt power over them, like they were weaklings under me and I was in control. It boosted my confidence to be the teacher in the situation and made me feel more desirable, heterosexual woman, age 25.
Another believed sex was a means of experiencing God:
I can’t really describe this experience, but pure joy and connection with another person I feel is becoming closer to the cycles of life and the underlying palpable energy of the world, in essence, God, heterosexual woman, age 21.
Through the voices of real women, wide-ranging scientific and clinical findings, and our own original research, women’s sexuality can be seen in all of its textures, whether a sexual encounter leads to pleasure, remorse, emotional connection, or transcendent love.
We believe the end result will aid more informed sexual decision making, when, how, and, of course, why to have sex, in a relationship or outside one. Although this is not designed as a “self-help” book, we believe that readers will glean information that they can use in their own lives and share with their sexual partners. We hope that this book provides readers with a new set of lenses for viewing the many nuanced facets of women’s sexual psychology.

One. What Turns Women On?

Scent, Body, Face, Voice, Movement, Personality, and, Yes, Humor.
Personal beauty is a greater recommendation than any letter of introduction, Aristotle.
Sexual attraction is an elixir of life, from love at first sight to the spark of romance that enlivens a relationship for years. It imbues the great love affairs of literature and film, whether the star-crossed lovers of Shakespeare’s Romeo and Juliet or James Cameron’s Titanic or the long-smoldering attraction between Humphrey Bogart’s and Ingrid Bergman’s characters in Casablanca. And despite the reigning conventional wisdom, the basic biochemistry of attraction is the number one reason women give for why they have sex.
Despite its relative neglect in the history of psychology, sexual attraction is not simply a topic of titillation. It permeates our conversations, from gossip columns highlighting celebrity fashion missteps to Web sites devoted to ranking who is hot and who is not, advertisers exploit it to sell everything from cars to iPods. Lack of sexual attraction is often a deal breaker in romances, killing possible partnerships before they even get off the ground. And when sexual attraction fades with time, it can propel a partner into the arms of another. For many, sex provides a deep sense of exhilaration that makes them feel alive. We often cannot describe what it is that attracts us to another person. Sometimes we resort to types, latching on to an easily identifiable trait or pointing to a celebrity who has many of the qualities we, and apparently many other people, find most appealing. Many women in our study mentioned a specific physical or personality characteristic that sexually attracted them, yet as many others chose to describe their sexual motivation in the simplest terms:
I was attracted to the person. Women also said the person had a beautiful face, the person had a desirable body, the person had beautiful eyes, the person smelled nice, the person’s physical appearance turned me on, the person was a good dancer, or more graphically, the person was too physically attractive for me to resist.
This chapter explores what, exactly, women find sexually attractive, and why. Why do musky aromas and resonant voices stir women’s sexual desires? If women really are less sexually stimulated by visual images than men are, why do the faces of, say, Antonio Banderas and George Clooney excite so many women? Is there actually something in the way another person moves that can affect women’s sexual drives? How can a dazzling personality sometimes turn an average Joe into a man who exudes an irresistible animal magnetism? When does physical attraction overpower everything else?
Because the spark of attraction often operates beneath our consciousness, some of our answers to these questions come from an evolutionary perspective. Evolutionary psychologists start with the working premise that at least some of the characteristics that women find attractive are not culturally arbitrary. (The same is true of the characteristics that men find attractive.) Could the qualities that define sex appeal unconsciously provide signals of the benefits a woman might get from a potential mate? Biologists distinguish two broad classes of evolutionary benefits. Genetic benefits are the high quality genes that can endow a woman’s children with a better ability to survive and reproduce. Resource benefits, including food, shelter from the hostile forces of nature, and physical protection from aggressive men, help a woman and her children to survive and thrive.
As we will see, some of the things that make women want to have sex with men have their roots in humans’ evolutionary past, while others have taken on a life of their own because of how we live, work, dress, and socialize today.
Where Attraction Begins.
People are constantly coming into contact with one another, we are nestled into adjoining seats in college lecture halls, bump into strangers at coffee shops, move into neighboring houses on suburban cul-de-sacs, or spend long hours in cattycorner cubicles at the office. This proximity is often the first step in becoming attracted to someone.
Historically, you can see this in who people choose as their mates. Back in the 1930s, a study examined five thousand marriages performed in a single year, 1931, to determine where the bride and groom lived before their wedding. One third lived within five blocks of each other and more than one half lived within a twenty-block radius. Several studies over the decades have uncovered similar patterns. For example, in classrooms with assigned seating, relationships develop as a function of how far people are seated from each other.
Students assigned to a middle seat are more likely to make acquaintances than those who are seated at the end of a row.
With alphabetical seating, friendships form between those whose names start with nearby letters.
Although being near someone does not guarantee that a sexual spark will be struck, repeated contact, up to a point, with someone increases the odds. One study found that a series of brief, that is, no more than thirty-five-second, face-to-face contacts without even talking to the person increased positive responses. That is, we tend to like the people we see often more than those we see less frequently. In another study, four women research assistants with comparable physical attractiveness attended a college class. One research assistant attended the class fifteen times during the semester, one assistant attended ten times, another five times, and one not at all. None of the women had any verbal contact with the students in the class. At the end of the semester, the students, both men and women, rated how much they liked each of the research assistants. Attraction increased as the number of exposures increased, even though all of the research assistants were fundamentally strangers to the people in the class.
As it turns out, some amount of familiarity creates liking whether you’re talking about a person, a drawing, a word in an unknown foreign language, a song, a new product being advertised, a political candidate, or even a nonsense syllable.
The more frequent a person’s exposure during the crucial early period of introduction, the more positive the response. Why?
We often respond to anyone or anything strange or novel with at least mild discomfort, if not a certain degree of anxiety.
With repeated exposure, our feelings of anxiety decrease, the more familiar we are with someone, the better we are able to predict his or her behavior and thus to feel more comfortable around the person.
Once people are in close proximity, eye contact becomes important. The effect of mutual eye gaze is especially strong for women and men who are “romantics” by nature, those who believe in love at first sight, love for “the one and only,” and love as the key to relationships. In one study, forty-eight women and men came to a lab and were asked to stare into each other’s eyes while talking. The effect of mutual gaze proved powerful. Many reported that deep eye contact with an opposite-sex stranger created feelings of intense love. As one woman in our study put it:
I find it very arousing when someone is mysterious and doesn’t give too much of themselves away upon cursory review. I once had sex with a man because he was looking at me longingly but wouldn’t say much. It was a very passionate experience, heterosexual woman, age 33.
Another study had strangers first reveal intimate details of their lives to each other for half an hour, and then asked them to stare into each other’s eyes for four minutes, without breaking eye contact or making any conversation. Participants again reported deep attraction to their study partners. Two of these total strangers even ended up getting married!
Too much familiarity, however, can backfire. Traits that are initially deemed positive can become a source of annoyance.
Men who were once described as “funny and fun” become “embarrassing in public.” An attractive “spontaneity”, transforms into an unattractive “irresponsibility,” “successful and focused” into “workaholic,” and “strong willed” into “stubborn.” Indeed, a certain amount of “mystery” can be sexually motivating for women, or for men for that matter. Not only can mystery stoke attraction, too much familiarity can quash it. As one woman said in her sexual memoir, “proximity can kill sex faster than fainting.”
Just as overexposure can douse the fire of sexual attraction, its opposite, novelty, can stoke its flames. Psychologist Daryl Bem sums it up with the phrase “the exotic becomes erotic.” Indeed, in college classes in which instructors ask women to list the qualities they find sexually attractive, “mysterious” invariably emerges on the list.
Humans come blessed with five known senses, sight, sound, smell, touch, and taste, and the sensory cues that enter into attraction tend to have greater effect with physical closeness. That’s particularly true when considering one of the strongest ingredients in sex appeal, one long neglected by the scientific community: women’s acute sense of smell.
The Scent of Sexiness.
Scents are famously known to carry strong psychological associations, think about how a whiff of a loved one’s favored perfume or cologne can bring to mind the person who wore it, along with a cascade of emotions. Partly, this is due to the unusual design of the olfactory nerve, which extends in a network throughout the brain, unlike the nerves carrying information for the other major senses, which are less wide ranging.
This architecture helps the brain to tie memories of emotional events with olfactory information. The emotion stirring aspect of smell is important, but smell also turns out to be surprisingly important to women when it comes to basic sexual attraction.
Using an instrument called the “Sensory Stimuli and Sexuality Survey,” researchers at Brown University found that women rate how someone smells as the most important of the senses in choosing a lover, edging out sight (a close second), sound, and touch. One woman in our study ranked the attractions of a sexual partner:
I was attracted to his smell, his eyes, and his demeanor. Also, his French accent, heterosexual woman, age 23.
How a woman smells to a man, in contrast, figures less heavily in his sexual attraction. Perhaps it is because men’s sense of smell is less acute than women’s. Perhaps it is because visual cues loom so much larger in what turns men on. And it’s not just that women think smell matters in whether they are attracted to someone, it’s that women’s sexual arousal is enhanced by good body odors, and killed by bad ones.
One reason why body odors play such an important role in women’s sexual attraction has come to scientific light only recently. The first clue came from an unusual discovery: that a woman’s olfactory acuity reaches its peak around the time of her ovulation, the narrow twenty-four-hour window during the monthly menstrual cycle in which she can become pregnant.
This led scientists to suspect that women’s sense of smell might play a role in reproduction. It was not until researchers began to explore the body’s defenses against disease, however, that the connection was made.
The genes responsible for immune functioning, fighting off disease-causing bacteria and viruses, are located within the major histocompatibility complex, or MHC, found on chromosome 6. Different people have different versions, or alleles, of these MHC genes, in the jargon of geneticists, the MHC genes are “polymorphic.” It turns out that women can benefit in two ways from mating with men who are dissimilar to themselves in MHC genes. First, a mate with dissimilar MHC genes likely has more dissimilar genes in general, and so finding an MHC-dissimilar person attractive might help to prevent inbreeding. Reproducing with close genetic relatives can be disastrous for the resulting children, leading to birth defects, lower intelligence, and other problems. But a second benefit of mating with someone with complementary MHC genes is that any resulting children will have better immune functioning, making them better able to fight off many of the parasites that cause disease.
The puzzle is how women could possibly be able to choose mates who have complementary MHC genes in order to give these benefits to their offspring. In a revealing study, Brazilian researchers had twenty-nine men wear patches of cotton on their skin for five days to absorb their sweat, and thus their body odors. A sample of twenty-nine women then smelled each cotton patch and evaluated the odor on a dimension from attractive to unattractive. Scientists identified the specific MHC complex of each man and woman through blood assays.
Women found the aromas of men who had an MHC complex complementary to their own smelled the most desirable. The odors of men who had an MHC complex similar to their own made them recoil in disgust. Amazing as it may seem, women can literally smell the scent of a gene complex known to play a key role in immune functioning.
This highly developed sense of smell can have a profound effect on women’s sexuality. University of New Mexico evolutionary psychologist Christine Garver-Apgar and her colleagues studied MHC similarity in forty-eight romantically involved couples. They found that as the degree of MHC similarity between each woman and man increased, the woman’s sexual responsiveness to her partner decreased.
Women whose partners had similar MHC genes reported wanting to have sex less often with them. They reported less motivation to please their partner sexually compared to the women romantically involved with men with complementary MHC genes. Perhaps even more disturbing to their mates (if they knew), women with MHC-similar partners reported more frequent sexual fantasies about other men, particularly at the most fertile phase of their ovulation cycle. And their sexual fantasies about other men did not just remain in their heads.
They found themselves in the arms of other men more often, reporting higher rates of actual sexual infidelity, a 50 percent rate of infidelity among couples who had 50 percent of their MHC alleles in common.
So when a woman says that she had sex with a man because he smelled nice, her sexual motivation has hidden roots in an evolutionary adaptation. At an unconscious level, women are drawn to men with whom they are genetically compatible.
Another reason why a man’s scent is so important comes from the unusual discovery that body symmetry has sexual allure. Most human bodies are bilaterally symmetrical: The left wrist generally has the same circumference as the right wrist, the left ear is generally as long as the right ear, from the eyes to the toes, the left and right halves of people’s bodies roughly mirror each other. Each individual, however, carries small deviations from perfect symmetry. Two forces can cause faces and bodies to become more asymmetrical. One is genetic, the number of mutations an individual has, which geneticists call mutation load. Although everyone carries some genetic mutations (estimates are that the average person has a few hundred), some people have a higher mutation load than others, and those with more mutations tend to be more asymmetrical. The second force is environmental. During development, some individuals sustain more illnesses, diseases, parasites, and bodily injuries than others, and these environmental insults create asymmetries in the body and face.
Symmetry, in short, is a sign of good health, an indication that a person carries a low mutation load and has experienced few environmental injuries, or at least possesses the capacity to sustain environmental injuries without their leaving much of a mark.
If body symmetry is attractive because of how we evolved, so is the fact that women are able to detect the scent signature for symmetry, a useful skill when you consider that some asymmetries may not be immediately visible.
But could a woman possibly smell body symmetry? In one study, men wore white cotton T-shirts for two nights. The Tshirts were then sealed in plastic bags. In the laboratory, scientists used calipers to measure the various physical components of the men’s bodies, including their wrists, ankles, and earlobes, in order to evaluate their degree of symmetry.
Then women smelled each T-shirt and provided a rating of how pleasant or unpleasant it smelled. Women judged the T shirt odors of symmetrical men to be the most attractive and deemed the odors of asymmetrical men to be repulsive. Four independent studies have replicated the finding.
Women find the scent of symmetry particularly attractive when they are in the fertile phase of their ovulation cycle, precisely the time in which they are most likely to conceive.
This apparently reflects an evolutionary adaptation in women to reproduce with men possessing honest signals of good health, including high-quality genes. When women have extramarital affairs, they tend to choose symmetrical men as partners, yet another indication of the importance of symmetry in sexual attraction.
The Power of a Man’s Musk.
A person’s scent can influence not only a woman’s mate choice, but also when and how frequently she chooses to have sex and possibly the chance she will become pregnant.
Researchers have shown that exposure to male pheromones can increase a woman’s fertility. Pheromones are substances secreted from the glands at the anus, underarms, urinary outlet, breasts, and mouth. In nonhuman mammals, a specialized olfactory structure, the vomeronasal organ, acts as the locus for receiving pheromonal signals, which control most animals’ and insects’ mating rituals. One study found that frequent sexual exposure to men (at least once a week) regularized women’s menstrual cycles, increased fertile basal body temperature, and increased estrogen in the phase of the menstrual cycle following ovulation, called the luteal phase.
Another study showed that women who slept with a man two or more times during a forty-day period had a significantly higher incidence of ovulation than those who had slept with a man less often.
Once again, sexual attraction plays a role. Doctor Winnifred Cutler, the director of the Athena Institute, found that exposure to male pheromones influences a woman’s sexual attraction to a man. In her study, thirty-eight heterosexual men aged twenty-six to forty-two recorded their baseline levels of sexual behavior and dating experiences for a two-week period. Then for a month they wore either their regular aftershave, or the same aftershave but with an added synthetic version of a pheromone naturally secreted by men. The men did not know which aftershave they were wearing. During the test month, the men continued to record their sexual and dating experiences. The results showed that compared to their baseline levels of sexual activity, the men who wore the “pheromone-charged” aftershave engaged in higher rates of sexual petting and intercourse, had more frequent informal dates, and spent more time sleeping next to a partner. Over the same period, they reported no change in their frequency of masturbation, so the increase in the rest of their sexual activity could not simply have resulted from men having a higher sex drive due to their own exposure to the extra pheromone.
Sensitivity to scent does not just provide a means for identifying good hygiene or emotionally resonant perfumes.
Scent also gives women cues about a partner’s immune system and body symmetry, and pheromones can unconsciously shape how women become sexually attracted and aroused.

Size Matters.
We’ve seen how body symmetry, because it indicates good health, is attractive to women. Body symmetry is also linked with men’s muscularity, and studies conducted both in the United States and on the Caribbean island of Dominica have found that symmetrical men have a larger number of sex partners than asymmetrical men. When women identify the specific qualities that attract them to a sexual partner, they frequently mention “the person had a desirable body”, the sixteenth most frequent reason cited for having sex in our original study. But what sorts of bodies do women find sexually desirable?
Perhaps the most obvious characteristic is height. Studies consistently find that women consider tall men to be attractive, although only to an extent, taller than average, but not too tall. In analyses of personal ads, 80 percent of women state a desire for a man six feet tall or taller. Men who indicated in their personal ads that they were tall received far more responses from women. Women prefer tall men as marriage partners, and place an even greater emphasis on height in shorter-term sex partners. Women even take height into consideration when selecting sperm donors!
A study of British men found that taller than average men have had a greater number of live-in girlfriends than their shorter peers. Two studies found that taller than average men tend to have more children, and hence are more reproductively successful. Women seem to find tall men better candidates for romance and reproduction.
Could there be a logic underlying women’s desires for tall men? In traditional cultures, tall men tend to have higher status. “Big men” in hunter-gatherer societies, high-status men who command respect, are literally big men, physically.
In Western cultures, tall men tend to have higher socioeconomic status than short men. Another study found that recruiters choose the taller of two applicants for a sales job 72 percent of the time. Each added inch of height adds several thousand dollars to a man’s annual salary. One study estimated that men who are six feet tall earn, on average, $166,000 more across a thirty-year career than men seven inches shorter.
Taller policemen are assaulted less often than shorter policemen, indicating that their stature either commands more respect from criminals or causes them to think twice before attacking. Height deters aggression from other men. In the jargon of evolutionary biology, height is an “honest signal” of a man’s ability to protect. Women report simply feeling safer with tall mates.
Another answer comes from recently discovered correlates of male height. Tall men, on average, tend to be healthier than short men, although men at the extreme high and low end of the distribution have more health problems. So tall men tend to have better job prospects, to have more economic resources, to enjoy elevated social status, to afford physical protection, and to be healthy, a bounty of adaptive benefits.
We will see how sizes in other arenas matter in chapters 2 and 7.

Fit for Sex.
Height, of course, is not the only aspect of men’s bodies that sexually excites women.
Studies of mate preferences reveal that women desire strong, muscular, athletic men for long-term mating as well as for sexual liaisons. Most women show a distinct preference for a particular body morphology, namely, a V-shaped torso that reveals a high shoulder-to-hip ratio (broad shoulders relative to hips). They are attracted to a lean stomach combined with a muscular (but not muscle-bound) upper torso.
In fact, both sexes judge men with a high shoulder-to-hip ratio to be more physically and socially dominant, which may give a clue to its appeal, since women generally are not attracted to men who appear as though they could be easily dominated by other men. Men exhibiting a high shoulder-tohip ratio begin having sexual intercourse at an early age, sixteen or younger. They report having more sex partners than their slim-shouldered peers. They have more sexual affairs with outside partners while in a relationship. And they report more instances of being chosen by already-mated women for sexual affairs on the side. Shoulder-to-hip ratio also arouses the green-eyed monster: Potential rivals with a high shoulder-to-hip ratio trigger jealousy in men.
Men with strong, athletic, V-shaped bodies tend to succeed in competitions with other men compared to their frailer peers.
Across cultures, physical contests such as wrestling, racing, and throwing allow women to gauge men’s physical abilities, including speed, endurance, and strength.
Scientific research, though, has discovered that men overestimate the degree of muscularity that women actually find attractive, assuming that they need to pump up more, or puff up more, to be attractive. One study compared the muscularity of men’s bodies in Cosmopolitan (whose readership is 89 percent women) with Men’s Health (whose readership is 85 percent men). Researchers rated the muscularity of men’s bodies depicted in each magazine. The level of muscularity depicted in Cosmopolitan (4.26) was nearly identical to the level of muscularity women rate as ideal in a sexual partner (4.49). Men, in contrast, mistakenly believe that women desire a more muscular sex partner (5.04), which corresponds more closely with the muscularity of men shown in Men’s Health (5.77).
Images of muscle-bound men have almost certainly fostered men’s misperception of what women find most sexually attractive, just as photo spreads of impossibly thin women have led women to overestimate the degree of thinness that men find most attractive. After viewing repeated images of V shaped bodies, men become more dissatisfied with their own bodies, just as women become more unhappy with their bodies after seeing images of size zero models. Fully 90 percent of American men report that they want to be more muscular. The figure among the less media-saturated Ghana is 49 percent.
Ukrainian men lie in between, with 69 percent reporting a desire to be more muscular. As one researcher summed it up, the average man “feels like Clark Kent but longs to be like Superman.”

The Face of Attraction.
He could have been a model. When he acted interested in me, I couldn’t believe it. We had sex once.
Strangely enough, he kept calling me afterward. I didn’t continue with the relationship for several reasons. One, he was just a pretty face, but I think he was really crazy about me. Two, never date a guy prettier than you are. It’s terrible for your self-esteem and your sanity, heterosexual woman, age 26.
Masculine facial features are heavily influenced by the production of testosterone during adolescence, when the bones in the face take their adult form. From an evolutionary perspective, puberty marks the time when men and women enter the arena of mate competition. They begin to allocate time, energy, and effort to the tasks of mate selection and mate attraction. In men, the amount of muscle mass, as we have seen, contributes to success in competition with other men and sexual attractiveness to women. And testosterone turns out to be the magical hormone that promotes men’s muscle mass and masculine facial features.
So why don’t all men have masculine faces and ripped bodies? The answer strangely hinges on a negative side effect of testosterone. High testosterone production compromises the body’s immune functioning, leaving men less able to fight off diseases and parasites. Now here is the paradox: Only men who are above average in healthiness during adolescence can “afford” to produce the high levels of testosterone that masculinize the face. Less healthy adolescents cannot afford to compromise their already precarious immune systems, and so produce lower levels of testosterone at precisely the time when facial bones take their adult form. A masculine-looking face signals a man’s health, his ability to succeed in competing with other men, and his ability to protect. And that is the best explanation for why most women find somewhat more masculine faces (but not the most masculine faces) to be the most attractive.
But when we consider a woman’s fertility status and whether she is evaluating a man as a casual sex partner or a husband, the dynamics shift. In a series of scientific studies, women were asked to judge the attractiveness of a variety of men’s faces at different points during their ovulation cycle, during the most fertile phase (the five days leading up to ovulation) and during the least fertile, post-ovulation luteal phase. The subjects evaluated the faces for sexiness, their attractiveness as a casual sex partner, and their attractiveness as a long-term mate. Women found above-average masculine faces to be the sexiest and the most attractive for a casual sexual encounter. In contrast, women judged somewhat less masculine faces to be more attractive for a long-term relationship. Women’s sexual desires for testosterone-fueled facial cues of masculinity were especially strong during the fertile window of their cycle.
The most plausible interpretation of these results is that women are attracted to men who are likely to be “good dads” when choosing long-term mates, but are attracted to the honest signals of health that masculinity provides when they are most likely to become impregnated. This interpretation, however, raises a puzzle: Why wouldn’t women be attracted to highly masculine males for all mating relationships, from dangerous liaisons through lifelong love?
The answer lies in the fact that the more masculine men are less sexually faithful. They are more likely to be the risk taking womanizing “bad boys” among the male population.
Consequently, most women face a trade-off: If they choose the less masculine-looking man, they get a better father and a more sexually loyal mate, but they lose out in the currency of genes for good health. If they choose the more masculine man, they can endow their children with good genes for health, but must suffer the costs of a man who channels some of his sexual energy toward other women. So women’s preferences reveal a dual mating strategy, an attempt to get the best of both worlds.
They can choose to have a long-term relationship with a slightly less masculine man who will be sexually loyal and invest in her children, while opportunistically having sex with the more masculine men when they are most likely to get pregnant. DNA fingerprinting studies reveal that roughly 12 percent of women get pregnant by men other than their long term mates, suggesting that some, but certainly not all, women pursue this dual mating strategy.
Cultures differ, however, in how much women are attracted to facial masculinity. Psychologist Ian Penton-Voak and his colleagues found that Jamaican women found masculine looking men sexier than did British women. They interpret this cultural difference as a product of the higher rates of infectious diseases in Jamaica compared to England. In cultures in which infectious disease is a more pervasive problem, women seem to shift their sexual choices to men who possess honest signals of good health, men whose faces have been shaped by testosterone.

Conventionally Handsome.
People are drawn to those who are collectively considered attractive, so much so that a number of women in our study reported having sex with attractive people even when they had no desire to pursue a long-term relationship:
I became friends with a man who was very handsome, but for whom I felt no desire to pursue a relationship. He asked me to stay the night in his bed, and despite having misgivings. I couldn’t resist. He was conventionally handsome but very edgy and nonconformist and he liked me a lot, predominantly heterosexual woman, age 36.
What does it mean for someone to be “conventionally” handsome? Developmental psychologist Judith Langlois studies the meaning of “attractiveness” in human faces by having subjects rate composite faces, made up of sixteen or more images morphed together, against the individual faces used to create the composites. The composite faces were rated more attractive, and, according to Langlois, if “you take a female composite (averaged) face made of thirty-two faces and overlay it on the face of an extremely attractive female model, the two images line up almost perfectly, indicating that the model’s facial configuration is very similar to the composites’ facial configuration.” The same was true of men’s composite faces.
Langlois has also found that infants as young as one year old respond to this kind of “averaged” attractiveness in adult faces. Researchers varied their attractiveness levels by putting on attractive and unattractive masks that were carefully and realistically molded to their faces. The men and women then interacted with, and attempted to initiate play with, the one year-olds. They discovered that the infants expressed more positive moods and were more involved in play when they interacted with the researchers who were wearing the attractive masks. Even when the stimulus is a doll, studies show that infants spend more time playing with attractive versus unattractive dolls.
There is also a large body of research showing that we are drawn to good-looking people because we make assumptions that they possess a whole host of other desirable traits. They are rated as also being interesting, sociable, independent, dominant, exciting, sexy, well adjusted, socially skilled, and successful. There is some support for these stereotypes.
Attractiveness is moderately linked with popularity, good interpersonal skills, and occupational success, and, to some extent, with physical health, mental health, and sexual experience, which may be partly because attractive people are treated more favorably.

A Knee-Knocking Voice.
Singers such as Elvis Presley in the Nineteen fifties, the Beatles in the Sixties, and Jim Morrison of the Doors in the seventies through contemporary rappers such as Kanye West, Jay-Z, and 50 Cent are, and have always been, famously attractive to women.
Part of their sex appeal has undoubtedly been a result of the popularity and social status they command. But there is also a sound of sexiness, something about male voices that gives women a sexual buzz.
Voice pitch is the most striking feature of human speech.
Before puberty, male and female voices are quite similar. At puberty, remarkable changes occur. Boys experience a dramatic increase in the length of their vocal folds, which become 60 percent longer than those of girls. Longer vocal folds and vocal tracts produce a deeper, more resonant voice pitch. Testosterone triggers the change in boys at puberty, and high levels of testosterone predict deeper voices among adult men.
The first scientific evidence of women’s preferences for deeper male voices came from a study in which women rated the deep, resonant voices such as that of Luciano Pavarotti more attractive than the higher-pitched voices such as that of Truman Capote. This may not come as much of a surprise. But three more recent investigations show that mating context is critical in how women choose among men’s voices.
Evolutionary anthropologist David Puts obtained voice recordings of thirty men attempting to persuade a woman to go out on a romantic date. Then 142 heterosexual women listened to the recordings and rated each man’s attractiveness in two mating contexts, for a short-term sexual encounter and for a long-term committed relationship. Although women said the deeper voices were more attractive in both mating contexts, they dramatically preferred the deeper voices when considering them as prospects for purely sexual, short-term encounters. Moreover, women in the fertile phase of their ovulation cycle showed the strongest sexual attraction to men with deep voices.
One hint as to why is found in studies of female frogs, which gravitate toward deep, resonant croaks of male bullfrogs, a reliable signal, for frogs, of a mate’s size and health. Now, research on people has revealed two similar reasons that help to explain why women find some men’s voices more attractive than others.
The first involves bilateral body symmetry, the health-and-good-genes signal that a person can better withstand the stresses of diseases, injuries, and genetic mutations during development. Body symmetry is more likely to produce deep voices. So when a woman finds the resonance of a man’s voice even sexier during her fertile, ovulatory phase, she is attracted to the sound of symmetry for her possible offspring.
Attractive-sounding voices also indicate a man’s body morphology. Psychologist Susan Hughes found that men with sexy voices, in contrast to their strident-sounding peers, have a higher shoulder-to-hip ratio, the attractive V-shaped body.
Women judge men with lower-pitched voices to be healthier, more masculine, more physically dominant, somewhat older, more socially dominant, and more well-respected by their peers.
Do women’s attractions to sexy voices translate into higher sexual success for lower-pitched men? One study found that American men with lower-pitched voices had experienced a larger number of sex partners than men with higher-pitched voices. A second study, of the Hadza, a population of hunter gatherers living in Tanzania, found that men with lower pitched voices had a greater number of children, possibly as a consequence of having greater sexual access to fertile women.
So it’s not that carrying a tune makes much difference, a baritone voice like the actor James Earl Jones’s might be mesmerizing because of all it signals about good health, good genes, the capacity to protect, and success in social hierarchies. Many of those sexually alluring musicians had another attractive quality to their credit, a body in motion.

Something in the Way He Moves.
Physical movement depends on the strength of a person’s bones, muscle tone, and motor control. The ability to move in a coordinated manner, especially through repetitive motions such as walking or dancing, reveals information about a person’s phenotype: It broadcasts information about age, notice the difference between the dancing prowess of younger versus older dancers. It also conveys information about energy level, health, and biomechanical efficiency, whether we know it or not.
We found that some women had sex with men simply because they were good dancers:
I was told that if a man could dance he could perform in bed. I did not believe this and wanted to see if it was true. I met someone who danced on the same order of a stripper. He danced for me a couple of times. We ended up having sex and yes he was as good in bed as he was on the dance floor. He literally danced while having sex. It was wonderful, heterosexual woman, age 29.
He was hot. The fact that he was a good dancer made him that much more appealing. I really enjoy dancing myself, so when I see that a person has rhythm, it turns me on, heterosexual woman, age 26.
Research reveals that women find certain body movements to be more attractive than others. One study had women view digitally masked or pixelated images of men dancing. Women were more attracted to men who displayed larger and more sweeping movements. They also rated these men more erotic.
Just as men’s faces differ from one another in their de