Of course, in addition to the obvious physical changes of puberty, the natural outcomes of this process include increased sexual drive and feelings of sexual attraction. Most children begin experiencing feelings of sexual attraction sometime during late childhood or early adolescence. The object of their attraction is usually a member of the opposite sex, but some youngsters are attracted to people of the same sex. A person's sexual orientation is his or her tendency to be attracted to people of the same sex (homosexual orientation), of the opposite sex (heterosexual orientation), or of both sexes (bisexual orientation). Why an individual develops a specific sexual orientation is a matter of great debate, as you are probably well aware. The basic issue is the same question we have discussed so often: What are the relative influences of nature (genetics and biology) and nurture (the environment in which a child develops), and how do these two factors interact?

Researchers estimate that from 2 to 10% of adults in the United States identify themselves as gay, lesbian, or bisexual (Patterson, 1995; Savin-Williams & Diamond, 2004; Savin - Williams & Ream, 2007). One study of young men who described themselves as homosexual or bisexual found that these men recalled experiencing feelings of same-sex attraction by the age of 10 and had their first homosexual experiences at around 14 (Savin-Williams, 1995).

Some differences between homosexual and heterosexual individuals are apparent during childhood. For example, homosexual men and women report having had cross-gender interests (e.g., preferring toys, activities, or clothing typically associated with the opposite sex) during childhood more often than heterosexuals. Children with gender identity disorder (in which a person is dissatisfied and uncomfortable with his or her biological sex) dress and behave in ways that are more typical of the opposite sex. These children are significantly more likely to develop a homosexual orientation than children without the disorder (Bailey & Zucker, 1995; Zucker & Bradley, 1995).

One model describes the development of a homosexual identity as progressing through four stages (Troiden, 1988):

  • Stage 1: Sensitization. In this stage, which usually occurs before puberty, a child has a general feeling of being different from his or her same-sex peers.
  • Stage 2: Identity confusion. Usually first experienced during adolescence, this stage involves a conflict between a teenager's prior self-image and his or her current feelings of same-sex arousal (or lack of heterosexual arousal).
  • Stage 3: Identity assumption. This stage often begins during the early twenties. The person defines and accepts himself or herself as homosexual and associates regularly with homosexual peer groups.
  • Stage 4: Commitment. This stage begins when the person enters a same-sex emotional and sexual relationship. The person adopts homosexuality "as a way of life," views a homosexual identity as a valid and satisfying self-identity, and may "come out" to others (Troiden, 1988, p. 110).

The developmental progression described in stage models such as this one seems to be more accurate for males than females in that fewer women report feeling different from same-sex peers during childhood, and more report first experiencing same-sex attraction after reaching adulthood rather than during adolescence (Diamond & Savin-Williams, 2000; Ruble et al., 2006). And while stage models imply that a homosexual identity remains stable once it is achieved, recent research indicates that there may be more changes over time than a stage model would predict, with shifts in sexual orientation both toward and away from same-sex attraction and behavior (Savin-Williams & Ream, 2007).

Descriptions of different childhood characteristics of heterosexual and homosexual individuals are interesting and indicate that orientations may begin to develop early in life—but they do not explain why children have these characteristics. There is increasing evidence that sexual orientation is influenced to some extent by biological factors. One source of evidence comes from case studies of children who are sexually reassigned during early infancy, with boys raised as girls, or vice versa. Though rare, this happens because of prenatal problems in the development of sex organs or accidents during circumcision. Despite early reports that these children grew up to be well-adjusted members of their assigned gender, follow-up studies found that many reverted to their biological sex in terms of sexual orientation, described themselves as bisexual, or experienced sexual dysfunction related to gender identity (Byne, 2006; Money & Ehrhardt, 1972; Mustanski, Chivers, & Bailey, 2002). In addition, twin studies have found a genetic influence. There is a higher concordance in homosexuality in identical than in fraternal twins, with heritability estimates ranging from .14 to .76 (Bailey & Pillard, 1991; Mustanski et al., 2002). Genetics studies identified a location on the X chromosome shared more often by brothers who were both homosexual than by heterosexual brothers (Hamer, 1999).

Prenatal hormone levels also play a role. For example, there is a relationship between abnormal prenatal hormone levels and later behavior, personality characteristics, and sexual orientation. Girls exposed to higher-than-normal prenatal levels of androgens (male hormones) tend to show traits and preferences more typical of males, and males exposed to lower-than-normal-levels of androgens show more female-typical patterns and choices (Berenbaum & Snyder, 1995; Dittman et al., 1990; Meyer-Bahlburg et al., 1995; Mustanski et al., 2002). And autopsy studies have found that some areas of the brains of homosexual men are more similar to those of heterosexual women than to the brains of heterosexual men. Remember, however, that differences in brain structure could result from biological factors or from differences in experience (LeVay, 1993; Mustanski et al., 2002).

But even a strong biological or genetic influence on a behavior does not mean that the environment is unimportant. The same twin studies that found moderate-to-strong heritability estimates also found estimates of the influence of nonshared environment that ranged from .14 to .73. There is also ample evidence that reinforcement, punishment, and observational learning influence gender-related behaviors and preferences.

One interesting theory tries to integrate the findings on biological and environmental influences (Bern, 1996, 2000). According to this exotic becomes erotic theory, adolescents begin to see exotic, or very different, attributes and behaviors as erotic, or sexually attractive. In this process biology exerts an indirect influence through temperamental characteristics such as activity level and aggressiveness. First, in the preschool and elementary school years, children who are by nature active and aggressive enjoy more active, rough, and energetic activities and peers—that is, more typically male interests and activities. Children with less active and less aggressive tendencies gravitate toward a more female-typical pattern. The key factor, according to this theory, is not a child's overall activity level and degree of aggressiveness, but how different the child feels from his or her own or opposite-sex peers during childhood. During childhood each group will tend to view the other as different (exotic) and undesirable, and these perceptions will cause arousal. Children interpret this arousal as dislike, discomfort, or sometimes even anger or fear. Puberty then changes things—a lot! At this point youngsters cognitively reinterpret the arousal and gradually come to experience it as attraction. As a result, most adolescents develop sexual attraction toward members of the group they have not identified themselves as belonging to.

Notice that this theory tries to explain both heterosexual and homosexual development. The groups that form during early and middle childhood are based not on gender but on traits like activity level and aggressiveness. More active and aggressive girls are more likely to identify with boys early on; less active and less aggressive boys are more likely to identify with girls. Some evidence supports the exotic becomes erotic theory. Gender segregation during early and middle childhood is very strong, and young children often describe the opposite sex as undesirable and different ("yucky," to use one 6-year-old's word). And, as we noted earlier, homosexual men and women report higher levels of childhood cross-gender play and preferences, as well as feelings of being different from others of their gender (Bailey & Zucker, 1995; Ruble et al., 2006). However, others have suggested that the process may work in the opposite way. That is, rather than behavioral differences leading to a feelings of being different from others of the same sex, it may be that feelings of being different lead to progressively more atypical gender behavior and a homosexual self-concept (Carver, Egan, & Perry, 2004; Hammack, 2005; Nicolosi & Byrd, 2002; Ruble et al., 2006). Clearly, the development of sexual identity is complex and more research is needed.