Most definitions of sexual orientation include a psychological component, such as the direction of an individual's erotic desire, or a behavioral component, which focuses on the sex of the individual's sexual partner/s. Some definitions include both components. Some people prefer simply to follow an individual's self-definition or identity.
Some scholars of sexology, anthropology and history have argued that social categories such as heterosexual and homosexual are not universal. Different societies may consider other criteria to be more significant than sex, including the respective age of the partners, whether partners assume an active or a passive sexual role, and their social status.
Sexual identity and sexual behavior are closely related to sexual orientation, but they are distinguished, with identity referring to an individual's conception of themselves, behavior referring to actual sexual acts performed by the individual, and orientation referring to "fantasies, attachments and longings. Individuals may or may not express their sexual orientation in their behaviors. People who have a homosexual sexual orientation that does not align with their sexual identity are sometimes referred to as closeted.
Sexual identity may also be used to describe a person's perception of his or her own sex, rather than sexual orientation. The term sexual preference has a similar meaning to sexual orientation, but is more commonly used outside of scientific circles by people who believe that sexual orientation is, in whole or part, a matter of choice.
From at least the late nineteenth century in Europe, there was speculation that the range of human sexual response looked more like a continuum than two or three discrete categories. 28-year-old Berlin sexologist Magnus Hirschfeld published a scheme in 1896 that measured the strength of an individual's sexual desire on two independent 10-point scales, A (homosexual) and B (heterosexual). A heterosexual individual may be A0, B5; a homosexual individual may be A5, B0; An asexual would be A0, B0; and someone with an intense attraction to both sexes would be A9, B9.
The Kinsey scale measures sexual orientation from 0 (exclusively heterosexual) to 6 (exclusively homosexual), with an additional category, X, for those with no sexual attraction to either women or men. Unlike Hirschfeld's scale, the Kinsey scale is one-dimensional. Simon LeVay wrote, "it suggests (although Kinsey did not actually believe this) that every person has the same fixed endowment of sexual energy, which he or she then divides up between same-sex and opposite-sex attraction in a ratio indicative of his or her own sexual orientation.
The degree in which sexuality can change varies from person to person. The Centre for Addiction and Mental Health has said "For some people, sexual orientation is continuous and fixed throughout their lives. For others, sexual orientation may be fluid and change over time. Research by Lisa Diamond has shown the sexual orientation is more fluid among bisexual women than lesbians.
Other organizations disagree with Fritz Klein. The American Psychological Association has stated that homosexuality "is not changeable." In 2001, the United States Surgeon General David Satcher issued a report maintaining that "there is no valid scientific evidence that sexual orientation can be changed.
Some people distinguish between
Mainstream medical organizations have made clear that ”sexual behavior does not necessarily equate to sexual orientation.“
The earliest writers on sexual orientation usually understood it to be intrinsically linked to the subject's own sex. For example, it was thought that a typical female-bodied person who is attracted to female-bodied persons would have masculine attributes, and vice versa. This understanding was shared by most of the significant theorists of sexual orientation from the mid nineteenth to early twentieth century, such as Karl Heinrich Ulrichs, Richard von Krafft-Ebing, Magnus Hirschfeld, Havelock Ellis, Carl Jung and Sigmund Freud, as well as many gender variant homosexual people themselves. However, this understanding of homosexuality as sexual inversion was disputed at the time, and through the second half of the twentieth century, gender identity came to be increasingly seen as a phenomenon distinct from sexual orientation. Transgender and cisgender people may be attracted to men, women, or both, although the prevalence of different sexual orientations is quite different in these two populations (see sexual orientation of transwomen). An individual homosexual, heterosexual or bisexual person may be masculine, feminine, or androgynous, and in addition, many members and supporters of lesbian and gay communities now see the "gender-conforming heterosexual" and the "gender-nonconforming homosexual" as negative stereotypes. However, studies by J Michael Bailey and KJ Zucker have found that a majority of gay men and lesbians report being gender-nonconforming during their childhood years.
The majority of transgender people today identify with the sexual orientation that corresponds with their gender; meaning that a transwoman who is solely attracted to women would often identify as a lesbian. Female-attracted transmen often consider themselves straight men, yet some participate in the lesbian community.
For these reasons, the terms gynephilia and androphilia are occasionally (but increasingly) used when referring to the sexual orientation of transgender and intersex people (and occasionally, cisgender people), because rather than focusing on the sex of the subject, they only describe that of the object of their attraction. The third common term that describes sexual orientation, bisexuality, makes no claim about the subject's sex or gender identity. (See also Pansexuality)
Sexual orientation sees greater intricacy when non-binary understandings of both sex (male, female, or intersex) and gender (man, woman, transgender, third gender, or gender variant) are considered. Sociologist Paula Rodriguez Rust (2000) argues for a more multifaceted definition of sexual orientation:
The multiple aspects of sexual orientation and the boundary-drawing problems already described create methodological challenges for the study of the demographics of sexual orientation. Determining the frequency of various sexual orientations in real-world populations is difficult and controversial.
In the oft-cited and oft-criticized Sexual Behavior in the Human Male (1948) and Sexual Behavior in the Human Female (1953), by Alfred C. Kinsey et al., people were asked to rate themselves on a scale from completely heterosexual to completely homosexual. Kinsey reported that when the individuals' behavior as well as their identity are analyzed, most people appeared to be at least somewhat bisexual – i.e., most people have some attraction to either sex, although usually one sex is preferred. According to Kinsey, only a minority (5-10%) can be considered fully heterosexual or homosexual. Conversely, only an even smaller minority can be considered fully bisexual (with an equal attraction to both sexes).
Kinsey's methods have been criticized as flawed, particularly with regard to the randomness of his sample population, which included a large number of prison inmates. Nevertheless, Paul Gebhard, subsequent director of the Kinsey Institute for Sex Research, reexamined the data in the Kinsey Reports and concluded that accounting for major statistical objections barely affected the results. Most modern scientific surveys find that the majority of people report a mostly heterosexual orientation. However, the relative percentage of the population that reports a homosexual orientation varies with differing methodologies and selection criteria. Most of these statistical findings are in the range of 2.8 to 9% of males, and 1 to 5% of females for the United States — this figure can be as high as 12% for some large cities and as low as 1% percent for rural areas). In gay villages such as The Castro in San Francisco, California, the concentration of self-identified homosexual people can exceed 40%.
Estimates for the percentage of the population that are bisexual vary widely, at least in part due to differing definitions of bisexuality. Some studies only consider a person bisexual if they are nearly equally attracted to both sexes, and others consider a person bisexual if they are at all attracted to the same sex (for otherwise mostly heterosexual persons) or to the opposite sex (for otherwise mostly homosexual persons). A small percentage of people are not sexually attracted to anyone (asexuality).
Dr. Angela Pattatucci, a clinical biologist said, "["Lifestyle"] is idiotic when applied to sexual orientation – would you refer to lefthandedness as an 'alternative lifestyle? – but the problem is that through misuse by the media and in political rhetoric it's become ubiquitous.... When reporters use it, it is simply intellectual laziness. But some people adore that word, and the reason is probably in many cases, I'm very sorry to say, that it is such an inaccurate description of homosexuality, implying that sexual orientation is something one chooses, something frivolous or faddish, determined by what you do, as opposed to an internal orientation that is a component of what you are."
Simon LeVay, a neuroscientist, has argued against scientists, including Dean Hamer, who claim that genetic research has proven that sexual orientation is not a choice. Referring to Hamer's testimony at a 1993 trial challenging Colorado's Amendment 2, which would have rescinded anti-discrimination laws prohibiting discrimination against homosexuals, LeVay wrote, "...the pressures of the trial drove the expert witnesses to take somewhat more extreme or simplified positions than they might otherwise have done. Hamer, for example, said at one point: "Since people don't choose their genes, they couldn't possibly choose their sexual orientation. The same goes for the question about changing. People can't change their genes. So that part of sexuality that is genetically influenced, of course, cannot be easily changed." This goes beyond the data in two respects. First, it seems to deny any possibility of choice even if the genetic influence is only partial. Yet it is possible to construct a hypothesis whereby both "gay genes" and a desire to be homosexual are necessary for a person actually to become homosexual. Second, it equates genetic loading with immutability, a connection that is open to challenge."
Because sexual orientation is complex and multi-dimensional, some academics and researchers, especially in Queer studies, have argued that it is a historical and social construction. In 1976 the historian Michel Foucault argued that homosexuality as an identity did not exist in the eighteenth century; that people instead spoke of "sodomy", which referred to sexual acts. Sodomy was a crime that was often ignored but sometimes punished severely (see sodomy law).
Foucault further argued that it was in the nineteenth century that homosexuality came into existence as practitioners of emerging sciences and arts sought to classify and analyze different forms of sexuality. Finally, Foucault argues that it was this emerging discourse that allowed some to claim homosexuality as a human identity.
Heterosexuality and homosexuality are terms often used in European and American cultures to encompass a person’s entire social identity, which includes self and personality. In Western cultures some people speak meaningfully of gay, lesbian, and bisexual identities and communities. In other cultures, homosexuality and heterosexual labels don’t emphasize an entire social identity or indicate community affiliation based on sexual orientation.
Some historians and researchers argue that the emotional and affectionate activities associated with sexual-orientation terms such as gay and straight change significantly over time and across cultural boundaries. For example, in many English-speaking nations it is assumed that same-sex kissing, particularly between men, is a sign of homosexuality, whereas various types of same-sex kissing are common expressions of friendship in other nations. Also, many modern and historic cultures have formal ceremonies expressing long-term commitment between same-sex friends, even though homosexuality itself is taboo within the culture.