Sex and Sexual Orientation

As mentioned in the introduction, sex assigned at birth refers to how one’s anatomy, physiology, hormones, and genetics are classified. Gender identity is a person’s sense of their own gender, or sociocultural classification (i.e., man, woman, or another gender) based on, or in opposition to, their sex assigned at birth (i.e., male, female, or intersex). Sexual orientation is an enduring pattern of romantic or sexual attraction (or a combination of these) to persons of the opposite sex or gender, the same sex or gender, or to both sexes or more than one gender. These attractions are generally subsumed under heterosexuality, homosexuality, and bisexuality, while asexuality (the lack of sexual attraction to others) is sometimes identified as the fourth category.)

According to the American Psychological Association, sexual orientation “also refers to a person’s sense of identity based on those attractions, related behaviors, and membership in a community of others who share those attractions.”^[1] As a sexual orientation, heterosexuality is “an enduring pattern of emotional, romantic, and/or sexual attractions” to persons of the opposite sex; someone who is heterosexual is commonly referred to as straight.^[2] As a sexual orientation, homosexuality is “an enduring pattern of emotional, romantic, and/or sexual attractions” to people of the same sex. The most common terms for homosexual people are lesbian for females and gay for males, but gay also commonly refers to both homosexual females and males. Bisexuality is romantic attraction, sexual attraction, or sexual behavior toward both males and females. It may also be defined as romantic or sexual attraction to people of any sex or gender identity, which is also known as pansexuality. Varying definitions and strong social norms about sexuality can make sexual orientation difficult to quantify.

While the majority of people identify as heterosexual, there is a sizable population of people within the United States who identify as either homosexual or bisexual. Research suggests that somewhere between three and 10% of the population identifies as homosexual (Kinsey, Pomeroy, & Martin, 1948; LeVay, 1996; Pillard & Bailey, 1995).

Figure 1. Between three and 10% of the adult population identifies as homosexual. (credit: Till Krech)

Issues of sexual orientation have long fascinated scientists interested in determining what causes one individual to be heterosexual while another is homosexual. For many years, people believed that these differences arose because of different socialization and familial experiences. However, research has consistently demonstrated that family backgrounds and experiences are very similar among heterosexuals and homosexuals (Bell, Weinberg, & Hammersmith, 1981; Ross & Arrindell, 1988).

Genetic and biological mechanisms have also been proposed, and the balance of research evidence suggests that sexual orientation has an underlying biological component. For instance, over the past 25 years, research has demonstrated gene-level contributions to sexual orientation (Bailey & Pillard, 1991; Hamer, Hu, Magnuson, Hu, & Pattatucci, 1993; Rodriguez-Larralde & Paradisi, 2009), with some researchers estimating that genes account for at least half of the variability seen in human sexual orientation (Pillard & Bailey, 1998). Other studies report differences in brain structure and function between heterosexuals and homosexuals (Allen & Gorski, 1992; Byne et al., 2001; Hu et al., 2008; LeVay, 1991; Ponseti et al., 2006; Rahman & Wilson, 2003a; Swaab & Hofman, 1990), and even differences in basic body structure and function have been observed (Hall & Kimura, 1994; Lippa, 2003; Loehlin & McFadden, 2003; McFadden & Champlin, 2000; McFadden & Pasanen, 1998; Rahman & Wilson, 2003b). In aggregate, the data suggest that to a significant extent, sexual orientations are something with which we are born.

Although the field once stigmatized non-heterosexual orientations, we now know that homosexuality and bisexuality are in no way related to mental health. Sexual orientation is neither chosen nor changed. Scientists do not know the exact cause of sexual orientation, but they theorize that it is caused by a complex interplay of genetic, hormonal, and environmental influences, and do not view it as a choice. Although no single theory on the cause of sexual orientation has yet gained widespread support, scientists favor biologically based theories. There is considerably more evidence supporting nonsocial, biological causes of sexual orientation than social ones, especially for males. While some people believe that homosexual activity is unnatural, scientific research shows that homosexuality is a normal and natural variation in human sexuality and is not in and of itself a source of negative psychological effects. There is insufficient evidence to support the use of psychological interventions to change sexual orientation.

Gender Identity

Many people conflate sexual orientation with gender identity because of stereotypical attitudes that exist about homosexuality. In reality, these are two related, but different, issues. Gender identity refers to one’s sense of being male or female. Generally, our gender identities correspond to our chromosomal and phenotypic sex, but this is not always the case. When individuals do not feel comfortable identifying with the gender associated with their sex assigned at birth, then they experience gender dysphoria. Gender dysphoria, which we explore in the next section, is a diagnostic category in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) that describes individuals who do not identify as the gender that most people would assume they are. This dysphoria must persist for at least six months and result in significant distress or dysfunction to meet DSM-5 diagnostic criteria. In order for children to be assigned this diagnostic category, they must verbalize their desire to become the other gender.

Cisgender is an umbrella term used to describe people whose sense of personal identity and gender corresponds with their birth sex, while transgender is a term used to describe people whose sense of personal identity does not correspond with their birth sex. Approximately 1.4 million U.S. adults or 0.6% of the population are transgender according to a 2016 report.^[3]

Many people who are classified as gender dysphoric seek to live their lives in ways that are consistent with their own gender identity. This involves dressing in opposite-sex clothing and assuming an opposite-sex identity. These individuals may also undertake transgender hormone therapy in an attempt to make their bodies look more like the opposite sex, and in some cases, they elect to have surgeries to alter the appearance of their external genitalia to resemble that of their gender identity (Figure 6). Transgender people who attempt to alter their bodies through medical interventions such as surgery and hormonal therapy are called transsexual individuals. They may also be known as male-to-female (MTF) or female-to-male (FTM). Not all transgender individuals choose to alter their bodies: many will maintain their original anatomy but may present themselves to society as another gender.

Figure 2. Chaz Bono, a transgender male, is a well-known person who transitioned from female to male. (a) In the 1970s, the world knew Chaz as Chastity Bono, the daughter of the famous entertaining duo Sonny and Cher; here young Chastity is pictured with Sonny. (b) Later in life, Chaz transitioned to align his physical body with his gender identity. (credit b: modification of work by "dvsross"/Flickr)

Cultural Factors in Sexual Orientation and Gender Identity

Gender is deeply cultural. Like race, it is a social construction with real consequences, particularly for those who do not conform to gender binaries. In order to describe gender as a concept, we need to expand the language we use to describe gender beyond “masculine” or “feminine.” Gender identity, or the way that one thinks about gender and self-identifies, can be woman, man, or genderqueer.

Gender expression, or how one demonstrates gender (based on traditional gender role norms related to clothing, behavior, and interactions) can be feminine, masculine, androgynous, or somewhere along a spectrum. Although gender has traditionally been considered in binary terms (male or female), increasingly gender is being seen as a spectrum; however, our vocabulary is still limited in terms of the ways in which we describe gender identity.

Issues related to sexual orientation and gender identity are very much influenced by sociocultural factors. Even the ways in which we define sexual orientation and gender vary from one culture to the next. While in the United States exclusive heterosexuality is viewed as the norm, there are societies that have different attitudes regarding homosexual behavior. In fact, in some instances, periods of exclusively homosexual behavior are socially prescribed as a part of normal development and maturation. For example, in parts of New Guinea, young boys are expected to engage in sexual behavior with other boys for a given period of time because it is believed that doing so is necessary for these boys to become men (Baldwin & Baldwin, 1989).

There is a two-gendered culture in the United States. We tend to classify an individual as either male or female. However, in some cultures there are additional gender variants resulting in more than two gender categories. For example, in Thailand, you can be male, female, or kathoey. A kathoey is an individual who would be described as intersexed or transgender in the United States (Tangmunkongvorakul, Banwell, Carmichael, Utomo, & Sleigh, 2010).