A person’s sexual orientation is his or her physical, mental, emotional, and sexual attraction to a particular sex (male or female). Sexual orientation is typically divided into at least four categories: heterosexuality, the attraction to individuals of the other sex; homosexuality, the attraction to individuals of the same sex; bisexuality, the attraction to individuals of either sex; and asexuality, no attraction to either sex. Heterosexuals and homosexuals may also be referred to informally as “straight” and “gay,” respectively. The United States is a heteronormative society, meaning it assumes sexual orientation is biologically determined and unambiguous. Consider that homosexuals are often asked, “When did you know you were gay?” but heterosexuals are rarely asked, “When did you know that you were straight?” (Ryle 2011).

According to current scientific understanding, individuals are usually aware of their sexual orientation between middle childhood and early adolescence (American Psychological Association 2008). They do not have to participate in sexual activity to be aware of these emotional, romantic, and physical attractions; people can be celibate and still recognize their sexual orientation. Homosexual women (also referred to as lesbians), homosexual men (also referred to as gays), and bisexuals of both genders may have very different experiences of discovering and accepting their sexual orientation. At the point of puberty, some may be able to announce their sexual orientations, while others may be unready or unwilling to make their homosexuality or bisexuality known since it goes against U.S. society’s historical norms (APA 2008).

Alfred Kinsey was among the first to conceptualize sexuality as a continuum rather than a strict dichotomy of gay or straight. He created a six-point rating scale that ranges from exclusively heterosexual to exclusively homosexual. See the figure below. In his 1948 work Sexual Behavior in the Human Male, Kinsey writes, “Males do not represent two discrete populations, heterosexual and homosexual. The world is not to be divided into sheep and goats … The living world is a continuum in each and every one of its aspects” (Kinsey 1948).

The Kinsey scale indicates that sexuality can be measured by more than just heterosexuality and homosexuality.

Later scholarship by Eve Kosofsky Sedgwick expanded on Kinsey’s notions. She coined the term “homosocial” to oppose “homosexual,” describing nonsexual same-sex relations. Sedgwick recognized that in U.S. culture, males are subject to a clear divide between the two sides of this continuum, whereas females enjoy more fluidity. This can be illustrated by the way women in the United States can express homosocial feelings (nonsexual regard for people of the same sex) through hugging, handholding, and physical closeness. In contrast, U.S. males refrain from these expressions since they violate the heteronormative expectation that male sexual attraction should be exclusively for females. Research suggests that it is easier for women violate these norms than men, because men are subject to more social disapproval for being physically close to other men (Sedgwick 1985).

There is no scientific consensus regarding the exact reasons why an individual holds a heterosexual, homosexual, or bisexual orientation. Research has been conducted to study the possible genetic, hormonal, developmental, social, and cultural influences on sexual orientation, but there has been no evidence that links sexual orientation to one factor (APA 2008). Research, however, does present evidence showing that homosexuals and bisexuals are treated differently than heterosexuals in schools, the workplace, and the military. In 2011, for example, Sears and Mallory used General Social Survey data from 2008 to show that 27 percent of lesbian, gay, bisexual (LGB) respondents reported experiencing sexual orientation-based discrimination during the five years prior to the survey. Further, 38 percent of openly LGB people experienced discrimination during the same time.

Much of this discrimination is based on stereotypes and misinformation. Some is based on heterosexism, which Herek (1990) suggests is both an ideology and a set of institutional practices that privilege heterosexuals and heterosexuality over other sexual orientations. Much like racism and sexism, heterosexism is a systematic disadvantage embedded in our social institutions, offering power to those who conform to hetereosexual orientation while simultaneously disadvantaging those who do not. Homophobia, an extreme or irrational aversion to homosexuals, accounts for further stereotyping and discrimination. Major policies to prevent discrimination based on sexual orientation have not come into effect until the last few years. In 2011, President Obama overturned “don’t ask, don’t tell,” a controversial policy that required homosexuals in the US military to keep their sexuality undisclosed. The Employee Non-Discrimination Act, which ensures workplace equality regardless of sexual orientation, is still pending full government approval. Organizations such as GLAAD (Gay & Lesbian Alliance Against Defamation) advocate for homosexual rights and encourage governments and citizens to recognize the presence of sexual discrimination and work to prevent it. Other advocacy agencies frequently use the acronyms LBGT and LBGTQ, which stands for “Lesbian, Gay, Bisexual, Transgender” (and “Queer” or “Questioning” when the Q is added).

Sociologically, it is clear that gay and lesbian couples are negatively affected in states where they are denied the legal right to marriage. In 1996, The Defense of Marriage Act (DOMA) was passed, explicitly limiting the definition of “marriage” to a union between one man and one woman. It also allowed individual states to choose whether or not they recognized same-sex marriages performed in other states. Imagine that you married an opposite-sex partner under similar conditions—if you went on a cross-country vacation the validity of your marriage would change every time you crossed state lines. In another blow to same-sex marriage advocates, in November 2008 California passed Proposition 8, a state law that limited marriage to unions of opposite-sex partners.

Over time, advocates for same-sex marriage won several court cases, laying the groundwork for legalized same-sex marriage across the United States, including the June 2013 decision to overturn part of DOMA in Windsor v. United States, and the Supreme Court’s dismissal of Hollingsworth v. Perry, affirming the August 2010 ruling that found California’s Proposition 8 unconstitutional. Same-sex marriage became legal nationwide on June 26, 2015, when the United States Supreme Court ruled in Obergefell v. Hodges that state-level bans on same-sex marriage were unconstitutional. The court ruled that the denial of marriage licenses to same-sex couples and the refusal to recognize those marriages performed in other jurisdictions violated the Due Process and the Equal Protection clauses of the Fourteenth Amendment of the Constitution.