4.3 Sexual Orientation

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LOQ 4-11 What has research taught us about sexual orientation?

sexual orientation an enduring sexual attraction toward members of one’s own sex (homosexual orientation), the other sex (heterosexual orientation), or both sexes (bisexual orientation).

As noted earlier in this chapter, we express the direction of our sexual interest in our sexual orientation our enduring sexual attraction toward others. Sexual orientation varies from exclusive interest in our own sex to complete interest in the other sex, with most people in one of those two distinct categories (Norris et al., 2016). Those of us attracted to people of

Cultures vary in their attitudes toward same-sex attractions. “Should society accept homosexuality?” Yes, say 88 percent of Spaniards, 80 percent of Canadians, 60 percent of Americans, and 1 percent of Nigerians (Pew, 2013). Women everywhere are more accepting than men. Yet whether a culture condemns or accepts same-sex unions, heterosexuality prevails and bisexuality and homosexuality exist. In most African countries, same-sex relationships are illegal. Yet the ratio of people who are lesbian, gay, or bisexual “is no different from other countries in the rest of the world,” reports the Academy of Science of South Africa (2015). A large number of Americans—13 percent of women and 5 percent of men—say they have had some same-sex sexual contact during their lives (Chandra et al., 2011). Still more have had an occasional same-sex fantasy. Far fewer (3.4 percent) identify themselves as lesbian, gay, bisexual, or transgender (Gates & Newport, 2012; Ward et al., 2014).

How many people in Europe and the United States are exclusively homosexual? About 10 percent, as the popular press has often assumed? Nearly 20 percent, as Americans, on average, estimated in a 2013 survey (Jones et al., 2014)? Actually, the figure is about 3 or 4 percent of men and 2 percent of women (Chandra et al., 2011; Herbenick et al., 2010; Savin-Williams et al., 2012). Bisexuality is rarer, at less than 1 percent (Ward et al., 2014). In one survey of 7076 Dutch adults, only 12 people said they were actively bisexual (Sandfort et al., 2001).

In tribal cultures in which homosexual behavior is expected of all boys before marriage, heterosexuality nevertheless persists (Hammack, 2005; Money, 1987). As this illustrates, homosexual behavior does not always indicate a homosexual orientation.

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DRIVEN TO SUICIDE In 2010, Rutgers University student Tyler Clementi jumped off this bridge after his roommate secretly recorded and broadcast his intimate encounter with another man on the Internet. Reports then surfaced of other gay teens who had reacted in a similarly tragic fashion after being taunted. Since 2010, Americans—especially those under 30—have been increasingly supportive of those with same-sex orientations.
Stan Honda/AFP/Getty Images

What does it feel like to have same-sex attractions in a majority straight culture? If you are heterosexual, imagine that you have found “the one”—a perfect partner of the other sex. How would you feel if you weren’t sure who you could trust with knowing you had these feelings? How would you react if you overheard people telling crude jokes about straight people, or if most movies, TV shows, and advertisements showed only same-sex relationships? How would you like hearing that many people wouldn’t vote for a political candidate who favors other-sex marriage? And how would you feel if children’s organizations and adoption agencies thought you might not be safe or trustworthy because you’re attracted to people of the other sex?

Facing such reactions, some gays and lesbians may at first try to ignore or deny their feelings, hoping their desires will go away. But they don’t go away. Especially during adolescence or when rejected by their parents, people may struggle against their same-sex attractions. Without social support, these teens’ self-esteem may fall, and feelings of anxiety and depression may increase (Becker et al., 2014; Kwon, 2013). Some may consider suicide (Plöderl et al., 2013; Ryan et al., 2009; Wang et al., 2012). Later, people may even try to change their nonheterosexual orientation through psychotherapy, willpower, or prayer. But the feelings typically persist, as do those of heterosexual people—who are similarly unable to change (Haldeman, 1994, 2002; Myers & Scanzoni, 2005).

Today’s psychologists therefore view sexual orientation as neither willfully chosen nor willfully changed. “Efforts to change sexual orientation are unlikely to be successful and involve some risk of harm,” declared a 2009 American Psychological Association report. In 1973, the American Psychiatric Association dropped homosexuality from its list of “mental illnesses.” In 1993, The World Health Organization did the same, as did Japan’s and China’s psychiatric associations in 1995 and 2001.

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Sexual orientation in some ways is like handedness. Most people are one way, some the other. A very few are truly ambidextrous. Regardless, the way we are endures, especially in men (Chivers, 2005; Diamond, 2008; Dickson et al., 2013). Women’s sexual orientation tends to be less strongly felt and more variable (Baumeister, 2000). This may help explain why more women than men report having had at least one same-sex sexual contact, even though males’ homosexuality rate exceeds the female rate (Chandra et al., 2011).

Why Do We Differ?

So, if we do not choose our sexual orientation and (especially for males) cannot change it, where do these preferences come from? See if you can predict the answers (Yes or No) to these questions:

  1. Is homosexuality linked with problems in a child’s relationships with parents, such as with an overpowering mother and a weak father, or a possessive mother and a hostile father?

  2. Does homosexuality involve a fear or hatred of people of the other sex, leading individuals to direct their desires toward members of their own sex?

  3. Is sexual orientation linked with levels of sex hormones currently in the blood?

  4. As children, were most homosexuals molested, seduced, or otherwise sexually victimized by an adult homosexual?

Hundreds of studies have indicated that the answers to these questions have been No, No, No, and No (Storms, 1983). In a search for possible environmental influences on sexual orientation, Kinsey Institute investigators interviewed nearly 1000 homosexual and 500 heterosexual people. They assessed almost every imaginable psychological cause of homosexuality—parental relationships, childhood sexual experiences, peer relationships, and dating experiences (Bell et al., 1981; Hammersmith, 1982). Their findings: Homosexual people were no more likely than heterosexual people to have been smothered by maternal love or neglected by their father. And consider this: If “distant fathers” were more likely to produce homosexual sons, then shouldn’t boys growing up in father-absent homes more often be gay? (They are not.) And shouldn’t the rising number of such homes have led to a noticeable increase in the gay population? (It has not.) Most children raised by gay or lesbian parents grow up to be heterosexual and well-adjusted adults (Gartrell & Bos, 2010).

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PERSONAL VALUES AFFECT SEXUAL ORIENTATION LESS THAN THEY AFFECT OTHER FORMS OF SEXUAL BEHAVIOR Compared with people who rarely attend religious services, for example, those who attend regularly are one-third as likely to have lived together before marriage. They also report having had many fewer sex partners. But (if male) they are just as likely to be homosexual (Smith, 1998).
Stephen J. Carrerra/AP Photo

Note that the scientific question is not “What causes homosexuality?” (or “What causes heterosexuality?”) but “What causes differing sexual orientations?” In pursuit of answers, psychological science compares the backgrounds and physiology of people whose sexual orientations differ.

What have we learned from a half-century’s theory and research? If there are environmental factors that influence sexual orientation after we’re born, we haven’t yet found them. The lack of evidence for environmental influences on homosexuality has led researchers to explore several lines of biological evidence:

SAME-SEX ATTRACTION IN OTHER SPECIES In Boston’s Public Gardens, caretakers solved the mystery of why a much-loved swan couple’s eggs never hatched. Both swans were female. In New York City’s Central Park Zoo, penguins Silo and Roy spent several years as devoted same-sex partners. Same-sex sexual behaviors have also been observed in several hundred other species, including grizzlies, gorillas, monkeys, flamingos, and owls (Bagemihl, 1999). Among rams, for example, some 7 to 10 percent (to sheep-breeding ranchers, the “duds”) display same-sex attraction by shunning ewes and seeking to mount other males (Perkins & Fitzgerald, 1997). Homosexual behavior seems a natural part of the animal world.

GAY-STRAIGHT BRAIN DIFFERENCES Might the structure and function of heterosexual and homosexual brains differ? With this question in mind, researcher Simon LeVay (1991) studied sections of the hypothalamus taken from deceased heterosexual and homosexual people. (The hypothalamus is a brain structure linked to sexual behavior.) As a gay scientist, LeVay wanted to do “something connected with my gay identity.” To avoid biasing the results, he did a blind study: He didn’t know which donors were gay or straight. After nine months of peering through his microscope at a cell cluster that varied in size among donors, he consulted the donor records. The cell cluster was reliably larger in heterosexual men than in women and homosexual men. “I was almost in a state of shock,” LeVay said(1994). “I took a walk by myself on the cliffs over the ocean. I sat for half an hour just thinking what this might mean.”

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JULIET AND JULIET Boston’s beloved swan couple, “Romeo and Juliet,” were discovered actually to be, as are many other animal partners, a same-sex pair.
John Tlumacki/The Boston Globe/Getty Images

It should not surprise us that brains differ with sexual orientation. Remember, everything psychological is also biological. But when did the brain difference begin? At conception? During childhood or adolescence? Did experience produce the difference? Or was it genes or prenatal hormones (or genes activating prenatal hormones)?

LeVay does not view this cell cluster as an “on-off button” for sexual orientation. Rather, he believes it is an important part of a brain pathway that is active during sexual behavior. He agrees that sexual behavior patterns could influence the brain’s anatomy. Neural pathways in our brain do grow stronger with use. In fish, birds, rats, and humans, brain structures vary with experience—including sexual experience (Breedlove, 1997). But LeVay believes it more likely that brain anatomy influences sexual orientation. His hunch seems confirmed by the discovery of a similar difference between the male sheep that do and do not display same-sex attraction (Larkin et al., 2002; Roselli et al., 2002, 2004). Moreover, such differences seem to develop soon after birth, perhaps even before birth (Rahman & Wilson, 2003).

“Gay men simply don’t have the brain cells to be attracted to women.”

Simon LeVay, The Sexual Brain, 1993

Since LeVay’s brain structure discovery, other researchers have reported additional differences in the way that gay and straight brains function. One is in an area of the hypothalamus that governs sexual arousal (Savic et al., 2005). When straight women were given a whiff of a scent derived from men’s sweat (which contains traces of male hormones), this area became active. Gay men’s brains responded similarly to the men’s scent. Straight men’s brains did not. For them, only a female scent triggered the arousal response. In a similar study, lesbians’ responses differed from those of straight women (Kranz & Ishai, 2006; Martins et al., 2005). Researcher Qazi Rahman (2015) sums it up: Compared to heterosexuals, “gay men appear, on average, more ‘female typical’ in brain pattern responses and lesbian women are somewhat more ‘male typical.’”

GENETIC INFLUENCES Three lines of evidence suggest a genetic influence on sexual orientation.

PRENATAL INFLUENCES Twins share not only genes, but also a prenatal environment. Recall that in the womb, sex hormones direct our development as male or female. A critical period for human brain development occurs in the second trimester (Ellis & Ames, 1987; Garcia-Falgueras & Swaab, 2010; Meyer-Bahlburg, 1995). A fetus (either male or female) exposed to typical female hormone levels during this period may be attracted to males in later life. When pregnant sheep were injected with testosterone during a similar critical period, their female offspring later showed homosexual behavior (Money, 1987).

“Modern scientific research indicates that sexual orientation is . . . partly determined by genetics, but more specifically by hormonal activity in the womb.”

Glenn Wilson and Qazi Rahman, Born Gay: The Psychobiology of Sex Orientation, 2005

A second important prenatal influence is the curious older-brother effect. Men with older brothers are somewhat more likely to be gay—about one-third more likely for each additional older brother (Blanchard, 2004, 2008a,b, 2014; Bogaert, 2003). If the odds of homosexuality are roughly 2 percent among first sons, they would rise to nearly 3 percent among second sons, 4 percent for third sons, and so on for each additional older brother (FIGURE 4.5). The older-brother effect seems to be biological. It does not occur among adopted brothers (Bogaert, 2006a). One possible explanation is that male fetuses may produce a substance that triggers a defensive response in the mother’s immune system. After each pregnancy with a male fetus, antibodies in her system may grow stronger and may prevent the fetal brain from developing in a typical male pattern. Curiously, the older-brother effect is found only among right-handed men.

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Figure 4.5: FIGURE 4.5 The older-brother effect These approximate curves depict a man’s likelihood of homosexuality as a function of the number of biological (not adopted) older brothers he has (Blanchard 2008a; Bogaert, 2006a). This correlation has been found in several studies, but only among right-handed men (as about 9 in 10 men are).

How Do We Differ? A Summary

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Taken together, the brain, genetic, and prenatal findings offer strong support for a biological explanation of sexual orientation (LeVay, 2011; Rahman & Koerting, 2008). Additional support comes from other gay-straight differences. Gays and lesbians appear to fall midway between straight females and males on several traits (LeVay, 2011; Rahman & Koerting, 2008). From birth on, gay males tend to be shorter and lighter than straight males. Women in same-sex marriages were mostly heavier than average at birth (Bogaert, 2010; Frisch & Zdravkovic, 2010). Gay-straight spatial abilities also differ. On mental rotation tasks such as the one in FIGURE 4.6, straight men tend to outscore straight women. The scores of gay men and lesbians fall in between (Rahman & Koerting, 2008; Rahman et al., 2004). But both straight women and gay men have outperformed straight men at remembering objects’ spatial locations in memory game tasks (Hassan &Rahman, 2007). TABLE 4.1 summarizes these and other gay-straight differences.

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Figure 4.6: FIGURE 4.6 Spatial abilities and sexual orientation Which of the four figures can be rotated to match the target figure at the top? Straight males tend to find this an easier task than do straight females, with gays and lesbians falling in between. (From Rahman et al., 2004, with 60 people tested in each group.)
Figure 4.6:

Question 4.9

Answer: Figures a and d.

Table 4.1: TABLE 4.1 Biological Correlates of Sexual Orientation

Gay-straight trait differences

Sexual orientation is part of a package of traits. Studies—some in need of replication—indicate that homosexuals and heterosexuals differ in the following biological and behavioral traits:

  • spatial abilities

  • fingerprint ridge counts

  • auditory system development

  • handedness

  • occupational preferences

  • relative finger lengths

  • gender nonconformity

  • age of onset of puberty in males

  • sleep length

  • physical aggression

  • walking style

On average (the evidence is strongest for males), results for gays and lesbians fall between those of straight men and straight women. Three biological influences—brain, genetic, and prenatal—may contribute to these differences.

Brain differences

  • One hypothalamic cell cluster is smaller in women and gay men than in straight men.

  • Gay men’s hypothalamus reacts as do straight women’s to the smell of sex-related hormones.

Genetic influences

  • Shared sexual orientation is higher among identical twins than among fraternal twins.

  • Sexual attraction in fruit flies can be genetically manipulated.

  • Male homosexuality often appears to be transmitted from the mother’s side of the family.

Prenatal influences

  • Altered prenatal hormone exposure may lead to homosexuality in humans and other animals.

  • Men with several older biological brothers are more likely to be gay, possibly due to a maternal immune-system reaction.

Although “much remains to be discovered,” concludes Simon LeVay (2011, p. xvii), “the same processes that are involved in the biological development of our bodies and brains as male or female are also involved in the development of sexual orientation.”

“There is no sound scientific evidence that sexual orientation can be changed.”

UK Royal College of Psychiatrists, 2009

image For an 8-minute overview of the biology of sexual orientation, see LaunchPad’s Video: Homosexuality and the Nature–Nurture Debate.

Retrieve + Remember

Question 4.10

Which THREE of the following five factors have researchers found to have an effect on sexual orientation?

  1. An overpowering mother

  2. Size of a certain cell cluster in the hypothalamus

  3. Prenatal hormone exposure

  4. A weak or distant father

  5. For right-handed men, having multiple older biological brothers

ANSWERS: b, c, e