Human Sexuality

In a British survey of 18,876 people, 1 percent were seemingly asexual, having “never felt sexually attracted to anyone at all” (Bogaert, 2004, 2006b).

As you’ve probably noticed, we can hardly talk about gender without talking about our sexuality. For all but the tiny fraction of us considered asexual, dating and mating become a priority from puberty on. Both our body and our mind affect our sexual feelings and behaviors.

The Physiology of Sex

Unlike hunger, sex is not an actual need. (Without it, we may feel like dying, but we will not.) Yet sex and hunger share this: The pleasure we take in eating is nature’s method of getting our body nourishment. The desires and pleasures of sex are nature’s clever way of enabling our species’ survival. Sex is part of life. Had this not been so for all your ancestors, you would not be reading this book. Life is sexually transmitted.

Hormones and Sexual Behavior

4-4 How do hormones influence human sexual motivation?

Among the forces driving sexual behavior are the sex hormones. The main male sex hormone is testosterone. The main female sex hormones are the estrogens, such as estradiol. Sex hormones influence us at many points in the life span:

In most mammals, sexual interest and fertility overlap. Females become sexually receptive when their estrogen levels peak at ovulation. By injecting female animals with estrogens, researchers can increase their sexual interest. Hormone injections do not manipulate male animals’ sexual behavior as easily because male hormone levels are more constant (Piekarski et al., 2009). Nevertheless, male hamsters that have had their testes (which manufacture testosterone) surgically removed will gradually lose much of their interest in receptive females. They gradually regain it if injected with testosterone.

Hormones also influence human sexual behavior, but in a looser way, and researchers are debating whether women’s preferences for masculine or dominant-seeming men varies across the menstrual cycle (Gildersleeve et al., 2013; Wood et al., 2012). Among women with mates, sexual desire rises slightly at ovulation (Pillsworth et al., 2004). One study invited women with partners to keep a diary of their sexual activity. On the days around ovulation, intercourse was 24 percent more frequent (Wilcox et al., 2004).

Research by Kristina Durante, Elizabeth Pillsworth, and others also suggests that ovulation motivates women to attract male partners by wearing sexier clothing and choosing products that enhance their sexual features (Durante et al., 2011; Pillsworth & Haselton, 2006). Small wonder, then, that men tend to rate ovulating women as more attractive.

More than other mammalian females, women are responsive to their own testosterone levels (van Anders & Dunn, 2009). (Recall that women have testosterone, though less than men have.) If a woman’s natural testosterone level drops, as happens with the removal of the ovaries or adrenal glands, her sexual interest may plummet (Davison & Davis, 2011; Lindau et al., 2007). But testosterone-replacement therapy can often restore sexual desire, arousal, and activity (Braunstein et al., 2005; Buster et al., 2005; Petersen & Hyde, 2011).

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Testosterone-replacement therapy also increases sexual functioning in men with abnormally low testosterone levels (Khera et al., 2011). But normal ups and downs in testosterone levels (from man to man and hour to hour) have little effect on sexual drive (Byrne, 1982). In fact, male hormones sometimes vary in response to sexual stimulation. One Australian study tested whether the presence of an attractive woman would affect heterosexual male skateboarders’ performance. The result? Their testosterone surged, as did their riskier moves and crash landings (Ronay & von Hippel, 2010). Thus, sexual arousal can be a cause as well as a result of increased testosterone levels.

Large hormonal surges or declines do affect men and women’s desire. These shifts take place at two predictable points in the life span, and sometimes at an unpredictable third point:

  1. During puberty, the surge in sex hormones triggers development of sex characteristics and interests. If this hormonal surge is prevented, sex characteristics and sexual desire do not develop normally (Peschel & Peschel, 1987). This happened in Europe during the 1600s and 1700s, when boy sopranos were castrated to preserve their voices for Italian opera.
  2. In later life, estrogen and testosterone levels fall. As sex hormone levels decline, the frequency of sexual fantasies and intercourse declines as well (Leitenberg & Henning, 1995).
  3. For some, surgery or drugs may cause hormonal shifts. After surgical castration, men’s sex drive typically falls as testosterone levels decline sharply (Hucker & Bain, 1990). When male sex offenders took a drug that reduced their testosterone level to that of a boy before puberty, they also lost much of their sexual urge (Bilefsky, 2009; Money et al., 1983).

To recap, as sex hormones rise and fall, they influence our sexual characteristics and behaviors. But biology alone cannot fully explain human sexual behavior. Hormones may fuel our sex drive, but psychological stimuli turn on the engine, keep it running, and shift it into high gear. Let’s now see just where that drive usually takes us.

RETRIEVE + REMEMBER

Question 4.5

The primary male sex hormone is ________. The primary female sex hormones are the _______.

testosterone; estrogens

The Sexual Response Cycle

4-5 What is the human sexual response cycle, and how do sexual dysfunctions and paraphilias differ?

A nonsmoking 50-year-old male has about a 1-in-a-million chance of a heart attack during any hour. This increases to merely 2-in-a-million in the two hours during and following sex (with no increase for those who exercise regularly). Compared with risks associated with heavy exertion or anger (see Chapter 10), this risk seems not worth losing sleep (or sex) over (Jackson, 2009; Muller et al., 1996).

In the 1960s, two researchers—gynecologist-obstetrician William Masters, and his colleague, Virginia Johnson (1966)—made head-lines with their studies of sexual behavior. They recorded the physiological responses of 382 female and 312 male volunteers who came to their lab to masturbate or have intercourse. With the help of this atypical sample of people able and willing to display arousal and orgasm while scientists observed, the researchers identified a four-stage sexual response cycle:

1. Excitement: The genital areas fill with blood, causing a woman’s clitoris and a man’s penis to swell. A woman’s vagina expands and secretes lubricant. Her breasts and nipples may enlarge.

2. Plateau: Excitement peaks as breathing, pulse, and blood pressure rates continue to rise. A man’s penis becomes fully engorged. Some fluid—frequently containing enough live sperm to enable conception—may appear at its tip. A woman’s vaginal secretion continues to increase, and her clitoris retracts. Orgasm feels imminent.

3. Orgasm: Muscles contract all over the body. Breathing, pulse, and blood pressure rates continue to climb. (Later studies showed that a woman’s arousal and orgasm aid conception. They help propel semen from the penis, position the uterus to receive sperm, and draw the sperm further inward [Furlow & Thornhill, 1996].) Men and women don’t differ much in the delight they receive from sexual release. PET scans have shown that the same brain regions are active in men and women during orgasm (Holstege et al., 2003a,b).

4. Resolution: The body gradually returns to its unaroused state as genital blood vessels release their accumulated blood. This happens relatively quickly if orgasm has occurred, relatively slowly otherwise. (It’s like the nasal tickle that goes away rapidly if you have sneezed, slowly otherwise.) Men then enter a refractory period, a resting period that lasts from a few minutes to a day or more. During this time, they cannot achieve another orgasm. Women have a much shorter refractory period, enabling them to have another orgasm if restimulated during or soon after resolution.

Sexual Dysfunctions and Paraphilias

Masters and Johnson had two goals: to describe the human sexual response cycle, and to understand and treat problems that prevent people from completing that cycle. Sexual dysfunctions impair sexual arousal or functioning. Some involve sexual motivation, especially lack of sexual energy and arousability. For men, one common problem (and the subject of many TV commercials) is erectile disorder, an inability to have or maintain an erection. Another is premature ejaculation, reaching a sexual climax before the man or his partner wishes. For some women, pain during attempted intercourse may prevent them from completing the sexual response cycle. Others may experience female orgasmic disorder, distress over infrequently or never having an orgasm. In surveys of some 35,000 American women, about 4 in 10 reported a sexual problem, such as female orgasmic disorder or low desire. Only about 1 in 8 said that the problem caused them personal distress (Lutfey et al., 2009; Shifren et al., 2008). Most women who have reported sexual distress have connected it with their emotional relationship with their sexual partner (Bancroft et al., 2003).

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Therapy can help men and women with sexual dysfunction. Behaviorally oriented therapy, for example, can help men learn ways to control their urge to ejaculate, or help women learn to bring themselves to orgasm. Starting with the introduction of Viagra in 1998 and now including Levitra and Cialis, erectile disorder has been routinely treated by taking a pill. Equally effective drug treatments for female sexual interest/arousal disorder are not yet available.

Sexual dysfunction involves problems with arousal or sexual functioning. People with paraphilias do experience sexual desire, but they direct it in unusual ways. The American Psychiatric Association only classifies such behavior as disordered if

The serial killer Jeffrey Dahmer had necrophilia, a sexual attraction to corpses. People with the paraphilic disorder pedophilia experience sexual arousal toward children who haven’t entered puberty. Those with exhibitionism derive pleasure from exposing themselves sexually to others, without consent.

Sexually Transmitted Infections

4-6 How can sexually transmitted infections be prevented?

Life is sexually transmitted, but so are STIssexually transmitted infections. Rates of STIs (also called STDs, for sexually transmitted diseases) have ballooned in recent years, especially in people under 25 (CASA, 2004). Teenage girls, because of their less mature biological development and lower levels of protective antibodies, are especially at risk (Dehne & Riedner, 2005; Guttmacher, 1994). A Centers for Disease Control study of sexually experienced 14- to 19-year-old U.S. females found 39.5 percent had STIs (Forhan et al., 2008).

To understand the mathematics of infection, imagine this scenario. Over the course of a year, Pat has sex with 9 people. Over the same period, each of Pat’s partners has sex with 9 other people, who in turn have sex with 9 others. How many “phantom” sex partners (past partners of partners) will Pat have? The actual number—511—is more than five times the estimate given by the average student (Brannon & Brock, 1993).

Condoms are very effective in blocking the spread of some STIs. When Thailand promoted 100 percent condom use by commercial sex workers, condom use soared from 14 to 94 percent over a four-year period. During that time, the number of bacterial STIs reported each year plummeted 93 percent—from 410,406 to 27,362 (WHO, 2000).

Condoms offer only limited protection against certain skin-to-skin STIs, such as herpes. But their ability to reduce other risks has saved lives (Medical Institute, 1994; NIH, 2001). When used by people with an infected partner, condoms have been 80 percent effective in preventing transmission of HIV (human immunodeficiency virus—the virus that causes AIDS) (Weller & Davis-Beaty, 2002; WHO, 2003). Women’s AIDS rates are increasing fastest, partly because the virus is passed from man to woman much more often than from woman to man. A man’s semen can carry more of the virus than can a woman’s vaginal and cervical secretions. The HIV-infected semen can also linger for days in a woman’s vagina and cervix, increasing her exposure time (Allen & Setlow, 1991; WHO, 2004).

Most Americans with AIDS have been in midlife and younger—ages 25 to 44 (U.S. Centers for Disease Control and Prevention, 2007). Given AIDS’ long incubation period, this means that many of these young people were infected as teens. In 2011, the death of 1.7 million people with AIDS worldwide left behind countless grief-stricken partners and millions of orphaned children (UNAIDS, 2013). In sub-Saharan Africa, home to two-thirds of those with HIV, medical treatment and care for the dying are sapping social resources. AIDS can be transmitted by other means, such as needle sharing during drug use, but its sexual transmission is most common.

Although many people think oral sex is “safe sex,” there is a significant link between oral sex and STIs, such as the human papilloma virus (HPV) (Ballini et al., 2012). Risks rise with the number of sexual partners (Gillison et al., 2012). Thanks to a relatively new vaccine, most HPV infections can now be prevented if people are vaccinated before they become sexually active.

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RETRIEVE + REMEMBER

Question 4.6

The inability to complete the sexual response cycle may be considered a _______ ____. Exhibitionism would be considered a _________ ________.

sexual dysfunction; paraphilic disorder.

Question 4.7

From a biological perspective, AIDS is passed more readily from women to men than from men to women. True or false?

False. AIDS is transmitted more easily and more often from men to women.

The Psychology of Sex

4-7 How do external and imagined stimuli contribute to sexual arousal?

Biological factors powerfully influence our sexual motivation and behavior. But despite the shared biology that underlies sexual motivation, the 281 expressed reasons for having sex (at last count) ranged widely—from “to get closer to God” to “to get my boyfriend to shut up” (Buss, 2008; Meston & Buss, 2007).

Our most important sex organ may be the one resting above our shoulders: our brain. Our sophisticated brain allows us to experience sexual arousal both from what is real and from what is imagined.

External Stimuli

© Andy Singer

Men and women become aroused when they see, hear, or read erotic material (Heiman, 1975; Stockton & Murnen, 1992). Gender matters. Men generally become aroused when erotic material aligns with the direction of their own sexual interests. Thus, heterosexual men’s arousal is greater when they watch men having sex with women than when they watch men having sex with men. Homosexual men show the opposite pattern.

Women’s arousal is more complicated, and the context and the intensity of the sexual experience matter more than the gender of the people they watch (Both et al., 2005; Laan et al., 1995b). Women—whether heterosexual or lesbian—become aroused when watching men having sex with women or watching women having sex with women (Chivers et al., 2004; Laan et al., 1995a).

“Condoms should be used on every conceivable occasion.”

Anonymous

Does viewing pornography produce any lingering effects? In some studies, people have viewed scenes in which women were forced to have sex and appeared to enjoy it. Those viewers were more accepting of the false idea that women like to be raped. Male viewers were also more willing to hurt women and to commit rape (Allen et al., 1995, 2000; Foubert et al., 2011; Malamuth & Check, 1981; Zillmann, 1989). Viewing pornography may also decrease people’s satisfaction with their own sexual partner (Lambert et al., 2012). What is more, the erotic material that increases arousal today won’t produce the same level of arousal a year from now. With repeated exposure to any stimulus, including an erotic stimulus, our response lessens—we habituate. During the 1920s, when Western women’s rising hemlines first reached the knee, many male hearts fluttered when viewing a woman’s leg. Today, many men wouldn’t notice.

Imagined Stimuli

Sexual arousal and desire can also be products of our imagination. People who are left with no genital sensation after a spinal cord injury can still feel sexual desire (Sipski et al., 1999; Willmuth, 1987). Three years after experiencing a spinal cord injury, 90 percent of men in one study were engaging in sexual intercourse (Donohue & Gebhard, 1995).

Wide-awake people become sexually aroused not only by memories of prior sexual activities but also by fantasies. About 95 percent of both men and women report having sexual fantasies. The sexual fantasies of men—whether straight or gay—tend to be more frequent, more physical, and less romantic than women’s. In books and videos, men also prefer less personal and faster-paced sexual content (Leitenberg & Henning, 1995).

Does fantasizing about sex indicate a sexual problem or dissatisfaction? No. If anything, sexually active people have more sexual fantasies.

Teen Pregnancy

4-8 What factors influence teenagers’ sexual behaviors and use of contraceptives?

Compared with European teens, American teens have a higher rate of STIs and also of teen pregnancy (Call et al., 2002; Sullivan/Anderson, 2009). What environmental factors contribute to teen pregnancy?

Eidos/Scripps Howard Photo Service

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  1. Minimal communication about birth control Many teenagers feel uncomfortable discussing contraception. But those who talk freely with their parents, and who are in an exclusive relationship with a partner with whom they communicate openly, are more likely to use contraceptives (Aspy et al., 2007; Milan & Kilmann, 1987). Jamie Lynn Spears, former television star and younger sister of pop icon Britney Spears, said she didn’t use birth control (and became pregnant at age 16) because “like many young girls, I was really scared to go to the doctor…I was on the Nickelodeon show, and it felt especially embarrassing to ask someone to put me on birth control.”
  2. Passion overwhelming self-control When sexually aroused, people perform poorly on measures of impulse control (Macapagal et al., 2006). Teens who intend to delay sexual activity may also delay using contraceptives. Sexual arousal reduces intentions to use contraception, such as condoms (Ariely & Loewenstein, 2006). If passion overwhelms intentions, unexpected sexual activity may result in pregnancy (Gerrard & Luus, 1995; MacDonald & Hynie, 2008). In one survey, 72 percent of sexually active 12- to 17-year-old American girls said they regretted having had sex (Reuters, 2000).
  3. Alcohol use Sexually active teens are typically alcohol-using teens (Mason et al., 2010; Zimmer-Gembeck & Helfand, 2008). And those who use alcohol prior to sex are less likely to use condoms (Kotchick et al., 2001). Alcohol disarms normal restraints by depressing the brain centers that control judgment, inhibition, and self-awareness.
  4. Mass media norms of unprotected promiscuity Media help write the social scripts that shape our expectations about how to act in social situations. So what sexual scripts do today’s media write on our minds? One script portrays the sexualization of girls (see Close-Up: The Sexualization of Girls). Another script plays out in video and online games. An analysis of the 60 top-selling video games found 489 characters, 86 percent of whom were males (like most of the game players). The female characters were much more likely than the male characters to be hypersexualized—partially nude or revealingly clothed, with large breasts and tiny waists (Downs & Smith, 2010). Television has freely modeled sexual activity in which partners were unmarried, with no prior romantic relationship, and little concern for birth control or STIs (Brown et al., 2002; Kunkel, 2001; Sapolsky & Tabarlet, 1991). Adolescents learn from these scripts. Controlled studies show that the more sexual content adolescents view, the more likely they are to perceive their peers as sexually active, to develop sexually permissive attitudes, and to experience early intercourse (Escobar-Chaves et al., 2005; Martino et al., 2005; Ward & Friedman, 2006).

What are the characteristics of teens who delay having sex?

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We have considered some biological, psychological, and social-cultural influences on human sexuality. Because of these influences, sexual motivation and behavior vary widely over time, across place, and among individuals (FIGURE 4.4).

FIGURE 4.4 Levels of analysis for sexual motivation Our sexual motivation is influenced by biological factors, but psychological and social-cultural factors play an even bigger role.
Petrenko Andriy/Shutterstock
SHARING LOVE For most adults, a sexual relationship fulfills not only a biological motive but also a social need for intimacy.
Image Source/Getty Images

It’s important to remember that scientific research on human sexuality does not aim to define the personal meaning of sex in our own lives. We could know every available fact about sex—that the initial spasms of male and female orgasm come at 0.8-second intervals, that systolic blood pressure rises some 60 points and respiration rate to 40 breaths per minute, that the female nipples expand 10 millimeters at the peak of sexual arousal—but fail to understand the human significance of sexual intimacy.

Sex is a socially significant act. Men and women can achieve orgasm alone. Yet most people find greater satisfaction—and experience a much greater surge in the prolactin hormone associated with sexual satisfaction and satiety—after intercourse and orgasm with their loved one (Brody & Tillmann, 2006). One study of 2035 married people found that couples who reported being in a deeply committed relationship before having sex also reported greater relationship satisfaction and stability—and better sex (Busby et al., 2010). Sex at its human best is life-uniting and love renewing.

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RETRIEVE + REMEMBER

Question 4.8

What factors influence our sexual motivation and behavior?

Influences include biological factors such as sexual maturity and sex hormones, psychological factors such as environmental stimuli and fantasies, and social-cultural factors such as the values and expectations absorbed from family and the surrounding culture.

Question 4.9

Which THREE of the following five factors contribute to unplanned teen pregnancies?

  • a. Alcohol use
  • b. Higher intelligence level
  • c. Unprotected sex
  • d. Mass media models
  • e. Increased communication about options

a, c, d

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In the rest of this chapter, we will consider two special topics: sexual orientation (the direction of our sexual interests), and evolutionary psychology’s explanation of our sexual motivation.

The Sexualization of Girls

C L O S E - U P

The Sexualization of Girls Surely you’ve noticed. Just about all media—TV, the Internet, music videos and lyrics, movies, magazines, sports media, and advertising—share a tendency. They portray women and even girls as sexual objects. The frequent result, according to the 2007 American Psychological Association (APA) Task Force on the Sexualization of Girls, is harm to their self-image and unhealthy sexual development. In 2010, the Scottish Parliament agreed.

© T.Arroyo/JPegFoto/PictureGroup via AP IMAGES

Sexualization occurs when girls

  • are led to value themselves in terms of their sexual appeal.
  • compare themselves to narrowly defined beauty standards.
  • see themselves as sexual beings for others’ use.

In experiments, the APA Task Force reported, being made self-conscious about one’s body, such as by wearing a swimsuit, disrupts thinking when doing math computations or logical reasoning. Sexualization also contributes to eating disorders, to depression, and to unrealistic expectations regarding sexuality.

Mindful of today’s sexualizing media, the APA has some suggestions for countering these messages. Parents, teachers, and others can teach girls “to value themselves for who they are rather than how they look.” They can teach boys “to value girls as friends, sisters, and girlfriends, rather than as sexual objects.” And they can help girls and boys develop media literacy skills that enable them to recognize and resist the message that women are sexual objects and that a thin, sexy look is all that matters.