AP Psychology

Module 53 - Sexual Development

LEARNING OBJECTIVES:
FOCUS QUESTION: How is our biological sex determined, and how do sex hormones influence prenatal and adolescent development?

In domains where we face similar challenges-regulating heat with sweat, preferring foods that nour1sh, growing calluses where the skin meets friction-men and women are similar. Even when describing the ideal mate, both prize traits such as“kind,"“honest," and“intelligent." But in mating-related domains, evolutionary psychologists contend, males differ from females whether they are elephants or elephant seals, rural peasants or corporate presidents (Geary, 2010). Our biology may influence our gender differences in two ways: genetically, by our differing sex chromosomes, and physiologically, from our differing concentrations of sex hormones.

Prenatal Sexual Development

As noted earlier, males and females are variations on a single form-of the 46 chromosomes, 45 are unisex. So great is this similarity that until seven weeks after conception, you were anatomically indistinguishable from someone of the other sex. Then your genes activated your biological sex. Male or female, your sex was determined by your father's contribution to your twenty-third pair of chromosomes, the two sex chromosomes. You received an X chromosome from your mother. From your father, you received the one chromosome that is not unisex-either another X chromosome, making you a girl, or a Y chromosome, making you a boy.

The Y chromosome includes a single gene which, about seven weeks after conception, throws a master switch triggering the testes to develop and to produce the principal male hormone, testosterone. This hormone starts the development of male sex organs. Females also have testosterone, but less of it.

Another key period for sexual differentiation falls during the fourth and fifth prenatal months. During this period, sex hormones bathe the fetal brain and influence its wiring. Different patterns for males and females develop under the influence of the male's greater testosterone and the female's ovarian hormones (Hines, 2004; Udry, 2000).

Adolescent Sexual Development

Pronounced physical differences emerge during adolescence, when boys and girls enter puberty and mature sexually. A surge of hormones triggers a two-year period of rapid physical development, usually beginning at about age 11 in girls and at about age 13 in boys. A year or two before that, however, boys and girls often feel the first stirrings of physical attraction (McClintock & Herdt, 1996).

About the time of puberty, boys' growth propels them to greater height than their female counterparts (FIGURE 53.1). During this growth spurt, the primary sex characteristics-the reproductive organs and external genitalia-develop dramatically. So do secondary sex characteristics, the nonreproductive traits such as breasts and hips in girls, facial hair and deepened voice in boys, and pubic and underarm hair in both sexes (FIGURE 53.2) .

In various countries, girls are developing breasts earlier (sometimes before age 10) and reaching puberty earlier than in the past. This phenomenon is variously attributed to increased body fat, increased hormone-mimicking chemicals, and increased stress related to family disruption (Biro et al., 2010).

Puberty's landmarks are the first ejaculation in boys (spermarche), usually by about age 14, and the first menstrual period in girls (menarche – meh-NAR-key), usually within a year of age 12 1/2 (Anderson et al., 2003). Menarche appears to occur a few months earlier, on average, for girls who have experienced stresses related to father absence, sexual abuse, or insecure attachments (Belsky et al., 2010; Vigil et al., 2005; Zabin et al., 2005). Girls who have been prepared for menarche usually experience it as a positive life transition. Studies have shown that nearly all adult women recall their first menstrual period and remember experiencing a mixture of feelings-pride, excitement, embarrassment, and apprehension (Greif & Ulman, 1982; Woods et al., 1983). Most men have similarly recalled their first ejaculation, which usually occurs as a nocturnal emission (Fuller & Downs, 1990).

Variations on Sexual Development

FOCUS QUESTION: What are some of the ways that sexual development varies?

Sometimes nature blurs the biological line between males and females. Atypical hormone exposure or sensitivity may cause atypical fetal development. Intersex individuals are born with intermediate or unusual combinations of male and female physical features. Genetic males, for example, may be born with normal male hormones and testes but without a penis or with a very small one.

Until recently, pediatricians and other medical experts often recommended surgery to create a female identity for these children. One study reviewed 14 cases of boys who had undergone early sex-reassignment surgery and had been raised as girls. Of those cases, 6 had later declared themselves as males, 5 were living as females, and 3 had an unclear gender identity (Reiner & Gearhart, 2004).

Although not born with an intersex condition, a little boy who lost his penis during a botched circumcision became a famous case illustrating the problems involved in sex-reassignment surgery. His parents followed a psychiatrist's advice to raise him as a girl rather than as a damaged boy. Alas,“Brenda" Reimer was not like most other girls.“She" didn't like dolls. She tore her dresses with rough-and-tumble play. At puberty she wanted no part of kissing boys. Finally, Brenda's parents explained what had happened, whereupon“Brenda" immediately rejected the assigned female identity. He cut his hair and chose a male name, David. He eventually married a woman and became a stepfather. And, sadly, he later committed suicide (Colapinto, 2000).

The bottom line:“Sex matters," concluded the National Academy of Sciences (2001). In combination with the environment, sex-related genes and physiology“result in behavioral and cognitive differences between males and females.“ Nature and nurture work together.

Sexually Transmitted Infections

FOCUS QUESTION: How can sexually transmitted infections be prevented?

Rates of sexually transmitted injections (STIs; also called STDs for sexually transmitted diseases) are rising, and two-thirds of the new infections have occurred in people under 25 (CASA, 2004). Teenage girls, because of their not yet fully mature biological development and lower levels of protective antibodies, are especially vulnerable (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).

Consider this: If someone uses a birth control method that is 98 percent effective in preventing pregnancy or infection, a 2 percent chance of failure in the first such use accumulates to a risk of nearly 50 percent after 30 such uses. Moreover, when people feel drawn to a partner, they become motivated to underestimate risks (Knauper et al., 2005) .

Condoms offer only limited protection against certain skin-to-skin STIs, such as herpes, but they do reduce other risks (Medical Institute, 1994; NIH, 2001). The effects were clear when Thailand promoted 100 percent condom use by commercial sex workers. Over a deficiency syndrome) a life4-year period, as condom use soared from 14 to 94 percent, the annual number of bacterial STIs plummeted from 410,406 to 27,362 (WHO, 2000) .

Across the available studies, condoms also have been 80 percent effective in preventing transmission of HW (human immunodeficiency virus-the virus that causes AIDS) from an infected partner (Weller & Davis-Beaty, 2002; WHO, 2003). Although AIDS can be transmitted by other means, such as needle sharing during drug use, its sexual transmission is most common. 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 the time of exposure (Allen & Setlow, 1991; WHO, 2004).

Most people recently diagnosed with AIDS in the United States have been ages 25 to 44 ~ (CDC, 2013a). Given AIDS' long incubation period, it's unsurprising that 39 percent of new HIV diagnoses in the United States were among those even younger – 13- to 29-year-olds (CDC, 2013b) . In 2009, the death of 1.8 million people with AIDS worldwide left behind countless grief-stricken partners and millions of orphaned children (UNAIDS, 2010). Sub-Saharan Africa is home to two-thirds of those infected with HN, and medical treatment and care for the dying are sapping the region's social resources.

Many people assume that oral sex falls in the category of“safe sex," but recent studies show a significant link between oral sex and transmission of STIs, such as the human papilloma virus (HPV). Risks rise with the number of sexual partners (Gillison et al., 2012). Most HPV infections can now be prevented with a vaccination administered before sexual contact.

Teen Pregnancy

FOCUS QUESTION: What factors influence teenagers' sexual behaviors and use of contraceptives?

Adolescents' physical maturation fosters a sexual dimension to their emerging identity. Yet sexual expression varies dramatically with time and culture. Among American women born before 1900, a mere 3 percent had experienced premarital sex by age 18 (Smith, 1998). A century later, about half of U.S. ninth-to twelfth-graders reported having had sexual intercourse (CDC, 2010). Teen intercourse rates are roughly similar in Western Europe and in Latin America, but much lower in Arab and Asian countries and among North Americans of Asian descent (McLaughlin et al., 1997; Wellings et al., 2006). Given the wide variation across time and place, it's no surprise that twin research has found that environmental factors accounted for almost three-fourths of the individual variation in age of sexual initiation (Bricker et al., 2006). Family and cultural values matter.

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

Minimal communication about birth control Many teenagers are uncomfortable discussing contraception with their parents, partners, and peers. Teens who talk freely with 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).

Guilt related to sexual activity In another survey, 72 percent of sexually active 12to 17-year-old American girls said they regretted having had sex (Reuters, 2000). Sexual inhibitions or ambivalence can restrain sexual activity, but if passion overwhelms intentions they may also reduce attempts at birth control (Gerrard & Luus, 1995; MacDonald & Hynie, 2008).

Alcohol use Sexually active teens are typically alcohol-using teens (Zimmer-Gembeck & Helfand, 2008), and those who use alcohol prior to sex are less likely to use condoms (Kotchick et al., 2001). By depressing the brain centers that control judgment, inhibition, and self-awareness, alcohol disarms normal restraints, a phenomenon well known to sexually coercive males.

Mass media norms of unprotected promiscuity Media help write the“social scripts" that affect our perceptions and actions. So what sexual scripts do today's media write on our minds? An average hour of prime-time television on the three major U.S. networks has contained 15 sexual acts, words, and innuendos. The partners were usually unmarried, with no prior romantic relationship, and few communicated any concern for birth control or STIs (Brown et al., 2002; Kunkel, 2001; Sapolsky & Tabarlet, 1991). The more sexual content adolescents view (even when controlling for other predictors of early sexual activity), 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) . (See Close-up: The Sexualization of Girls.)

Recently, there has been a greater emphasis on teen abstinence within some comprehensive sex-education programs. A government-commissioned study of four urban, school-based abstinence programs found that 49 percent of students not participating had sex over the next four to six years. And how many participating in the abstinence programs did so? An identical 49 percent (Trenholm et al., 2007). A National Longitudinal Study of Adolescent Health followed abstinence pledgers and nonpledgers (matched samples of similarly conservative teens who had never had sex). Five years later, the pledgers-82 percent of whom denied having ever pledged-were just as likely to have had premarital sex (Rosenbaum' 2009). However, a more recent experiment offered African-American middle school students an abstinence education program rooted in social psychological theory and research. In the ensuing two years, only 34 percent of those who participated started having sex, compared with 49 percent of those randomly assigned to a health promotion control group Gemmott et al., 2010).

The National Longitudinal Study of Adolescent Health among 12,000 teens found several factors that predicted sexual restraint:

Close-up: The Sexualization of Girls

As you have surely noticed, TV, the Internet, music videos and lyrics, movies, magazines, sports media, and advertising often portray women and even girls as sexual objects. The frequent result, according to both an American Psychological Association task force (2007) and the Scottish Parliament (2010), is harm to their self-image, and unhealthy sexual development. Sexualization occurs when girls

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 and 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.

Sexual Orientation

FOCUS QUESTION: What has research taught us about sexual orientation?

We express the direction of our sexual interest in our sexual orientation-our enduring sexual attraction toward members of our own sex (homosexual orientation), the other sex (heterosexual orientation), or both sexes (bisexual orientation). As far as we know, all cultures in all times have been predominantly heterosexual (Bullough, 1990). Some cultures have condemned same-sex relations. (In Kenya and Nigeria, 98 percent have thought homosexuality is“never justified" [Pew, 2006].) Others have accepted same-sex marriage, which by 2013 had become legal in 14 countries. But in both cases, heterosexuality prevails and homosexuality endures.

How many people are exclusively homosexual? About 10 percent, as the popular press has often assumed? Nearly 25 percent, as average Americans estimated in a 2011 Gallup survey (Morales, 2011)? Not according to more than a dozen national surveys that have explored sexual orientation in Europe and the United States, using methods protecting the respondents' anonymity. The most accurate figure seems to be about 3 percent of men and 1 or 2 percent of women, or perhaps a tad more if allowing for some underreporting (Chandra et al., 2011; Gates & Newport, 2012; Herbenick et al., 2010a,b). Fewer than 1 percent of survey respondents-for example, only 12 people out of 7076 Dutch adults in one survey (Sandfort et al., 2001) have reported being actively bisexual. A larger number of adults – 13 percent of women and 5 percent of men in a U.S. National Center for Health Statistics survey – report some same-sex sexual contact during their lives (Chandra et al., 2011). And still more have had an occasional homosexual fantasy.

What does it feel like to be the“odd man (or woman) out" in a heterosexual culture? If you are heterosexual, one way to understand is to imagine how you would feel if you were socially isolated for openly admitting or displaying your feelings toward someone of the other sex. How would you react if you overheard people making crude jokes about heterosexual people, or if most movies,1V shows, and advertisements portrayed (or implied) homosexuality? And how would you answer if your family members were pleading with you to change your heterosexual lifestyle and to enter into a homosexual marriage?

Facing such reactions, homosexual people often struggle with their sexual orientation. They may at first try to ignore or deny their desires, hoping they will go away. But they don't. The feelings typically persist, as do those of heterosexual people-who are similarly incapable of becoming homosexual (Haldeman, 1994, 2002; Myers & Scanzoni, 2005).

Most of 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. Some have noted that rates of depression and attempted suicide are higher among gays and lesbians. Many psychologists believe, however, that these symptoms may result from experiences with bullying, harassment, and discrimination (Sandfort et al., 2001; Warner et al., 2004).“Homosexuality, in and of itself, is not associated with mental disorders or emotional or social problems," declared the American Psychological Association (2007) .

Thus, sexual orientation in some ways is like handedness: Most people are one way, some the other. A very few are ambidextrous. Regardless, the way one is endures.

This conclusion is most strongly established for men. Compared with men's sexual orientation, women's tends to be less strongly felt and may be more variable (Chivers, 2005; Diamond, 2008; Peplau & Garnets, 2000). Men's lesser erotic plasticity (sexual variability) is apparent in many ways (Baumeister, 2000). Adult women's sexual drive and interests are more flexible and varying than are adult men's. Women, more than men, for example, prefer to alternate periods of high sexual activity with periods of almost none. They are also more likely than men to feel and act on bisexual attractions (Mosher et al., 2005).

Environment and Sexual Orientation

So, our sexual orientation is something we do not choose and (especially for males) seemingly cannot change. Where then, do these preferences come from? Let's look first at possible environmental influences on sexual orientation. To see if you can anticipate the conclusions that have emerged from hundreds of studies, try answering Yes or No to these questions: 1. Is homosexuality linked with problems in a child's relationships with parents, such as with a domineering mother and an ineffectual father, or a possessive mother and a hostile father?

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?

Is sexual orientation linked with levels of sex hom10nes currently in the blood?

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

The answer to all these questions has been No (Storms, 1983). In a search for possible environmental influences on sexual orientation, Kinsey Institute investigators interviewed nearly 1000 homosexuals and 500 heterosexuals. They assessed nearly every imaginable psychological cause of homosexuality – parental relationships, childhood sexual experiences, peer relationships, and dating experiences (Bell et al., 1981; Hammersmith, 1982). Their findings: Homosexuals were no more likely than heterosexuals to have been smothered by maternal love or neglected by their father. And consider this: If“distant fath'ers" 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 straight and well-adjusted (Gartrell & Bos, 2010).

A bottom line has emerged from a half-century's theory and research: If there are environmental factors that influence sexual orientation, we do not yet know what they are.

Biology and Sexual Orientation

The lack of evidence for environmental causes of homosexuality has motivated researchers to explore possible biological influences. They have considered evidence of homosexuality in other species, gay-straight brain differences, genetics, and prenatal hormones.

SAME-SEX ATTRACTION IN OTHER SPECIES

In Boston's Public Gardens, caretakers have solved the mystery of why a much-loved swan couple's eggs never hatch. Both swans are female. In New York City's Central Park Zoo, penguins Silo and Roy spent several years as devoted same-sex partners. At least occasional same-sex relations have been observed in several hundred species (Bagemihl, 1999). Grizzlies, gorillas, monkeys, flamingos, and owls are all on the long list. 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). Some degree of homosexual behavior seems a natural part of the animal world.

GAY-STRAIGHT BRAIN DIFFERENCES

Researcher Simon LeVay (1991) studied sections of the hypothalamus (a brain structure linked to emotion) taken from deceased heterosexual and homosexual people. As a gay man, LeVay wanted to do“something connected with my gay identity." To avoid biasing the results, he did a blind study, without knowing which donors were gay or straight. After 9 months of peering through his microscope at a hypothalamus cell cluster that seemed to come in different sizes, 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."

It should not surprise us that brains differ with sexual orientation. Remember, everything psychological is simultaneously 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 via 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 found between the 7 to 10 percent of male sheep that display same-sex attraction and the 90+ percent attracted to females (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).

Since LeVay's discovery, other researchers have reported additional gay-straight brain activity differences. One is 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. They showed the arousal response only to a female hormone sample. In a similar study, lesbians' responses differed from those of straight women (Kranz & Ishai, 2006; Martins et al., 2005).

GENETIC INFLUENCES

Three lines of evidence suggest a genetic influence on sexual orientation. FAMILYSTUDIES Researchers have speculated about possible reasons why“gay genes" might persist in the human gene pool, given that same-sex couples cannot naturally reproduce. One possible answer is kin selection. Recall from Module 15 the evolutionary psychology reminder that many of our genes also reside in our biological relatives. Perhaps, then, gay people's genes live on through their supporting the survival and reproductive success of their nieces, nephews, and other relatives (who also carry many of the same genes). Gay men make generous uncles, suggests one study of Samoans (Vasey & VanderLaan, 2010).

An alternative“fertile females" theory suggests that maternal genetics may also be at work (Bocklandt et al., 2006). Homosexual men tend to have more homosexual relatives on their mother's side than on their father's (Camperio-Ciani et al., 2004, 2009; Zietsch et al., 2008). And the relatives on the mother's side also produce more offspring than do the maternal relatives of heterosexual men. Perhaps the genes that dispose women to be strongly attracted to men, and therefore to have more children, also dispose some men to be attracted to men (LeVay, 2011). TWIN STUDIES Twin studies indicate that genes influence sexual orientation. Identical twins (who have identical genes) are somewhat more likely than fraternal twins (whose genes are not identical) to share a homosexual orientation (Alanko et al., 2010; Langstrüm et al., 2008, 2010). However, because sexual orientation differs in many identical twin pairs (especially female twins), other factors must also playa role. FRUIT FLY STUDIES Laboratory experiments on fruit flies have altered a single gene and changed the flies' sexual orientation and behavior (Dickson, 2005). During courtship, females acted like males (pursuing other females) and males acted like females (Demir & Dickson, 2005). With humans, it's likely that multiple genes, possibly in interaction with other influences, shape sexual orientation. In search of such genetic markers, one study financed by the U.S. National Institutes of Health is analyzing the genes of more than 1000 gay brothers. PRENATAL INFLUENCES

Twins share not only genes, but also a prenatal environment. Two sets of findings indicate that prenatal environment matters.

First, in humans, a critical period for brain development seems to fall between the middle of the second and fifth months after conception (Ellis & Ames, 1987; Gladue, 1990; Meyer-Bahlburg, 1995). Exposure to the hormone levels typically experienced by female fetuses during this period may predispose a person (female or male) to 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).

Second, the mother's immune system may playa role in the development of sexual orientation. Men who have older brothers are somewhat more likely to be gay-about one-third more likely for each additional older brother (Blanchard, 1997, 2008; 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 (see FIGURE 53.3). The reason for this curious effect – called the older-brother or fraternal birth-order homosexuality effect – is unclear. But the explanation does seem biological. The effect does not occur among adopted brothers (Bogaert, 2006). Researchers suspect the mother's immune system may have a defensive response to substances produced by male fetuses. After 4 each pregnancy with a male fetus, the maternal antibodies may become stronger and may 2 prevent the fetal brain from developing in a typical male pattern.

GAY-STRAIGHT TRAIT DIFFERENCES

On several traits, gays and lesbians appear to fall midway between straight females and males (TABLE 53.1 ; see also LeVay, 2011; Rahman & Koerting, 2008). Gay men tend to be shorter and lighter than straight men – a difference that appears even at birth. Women in same-sex marriages were mostly heavier than average at birth (Bogaert, 2010; Frisch & Zdravkovic, 2010). Data from 20 studies have also revealed handedness differences: Homosexual participants were 39 percent more likely to not be right-handed (Blanchard, 2008; Lalumiere et al., 2000).

Gay-straight spatial abilities also differ. On mental rotation tasks such as the one illustrated in FIGURE 53.4 (Vandenberg & Kuse, 1978), straight men tend to outscore straight women but the scores of gays and lesbians fall between those of straight men and women (Rahman et al., 2003). But straight women and gays both outperform straight men at remembering objects' spatial locations in tasks like those found in memory games (Hassan & Rahman, 2007).

* * *

The consistency of the brain, genetic, and prenatal findings has swung the pendulum toward a biological explanation of sexual orientation (LeVay, 2011; Rahman & Koerting, 2008) . 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."

Before You Move On

ASK YOURSELF: What have been your best and worst experiences during adolescence? How have your experiences been influenced by environmental factors, such as your cultural context, and how have they been influenced by your inborn traits?

TEST YOURSELF: How has the transition from childhood to adulthood changed in Western cultures in the last century or so?