Sexual orientation

• 1. Introduction

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  Sexual orientation is described by the American Psychological Association as an enduring pattern of emotional, romantic, and sexual attractions to men, women, or both sexes. That definition sounds settled. The reality underneath it is anything but. Consider a single sentence that Alfred Kinsey and his colleagues published in 1948. The world is not to be divided into sheep and goats. Not all things are black nor all things white. They were arguing that human desire runs along a continuum, not into two tidy boxes. That claim sits at the heart of a question scientists, sexologists, philosophers, and lawmakers have wrestled with for more than a century. What is sexual orientation, and how would you even measure it? Why do researchers favor biological explanations for it. Why does the prevalence of homosexuality in a population shift depending on which question you ask. And why did a sexologist named John Money decide the older phrase, sexual preference, had to go.

• 2. Identity Versus Behavior

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  John Money introduced the term sexual orientation in place of sexual preference, arguing that attraction is not necessarily a matter of free choice. The word preference, he held, smuggled in the idea of voluntary decision. The American Psychological Association's Committee on Gay and Lesbian Concerns went further. It listed sexual preference as wording that advances a heterosexual bias.

  The distinction matters because orientation, identity, and behavior are three separate things. Orientation, in one phrasing, refers to fantasies, attachments and longings. Sexual identity is an individual's conception of themselves. Behavior is the actual sexual acts a person performs. The three do not always line up.

  Scientists have a vocabulary for the mismatch. When a person's attractions, behaviors, and identity match, researchers call it concordance; when they diverge, discordance. A woman attracted to other women, who calls herself heterosexual and has sexual relations only with men, experiences discordance between her orientation and her identity and behavior. People whose non-heterosexual orientation does not align with their identity are sometimes called closeted.

  The American Psychological Association draws one more line. It distinguishes biological sex, the anatomical and genetic characteristics of being male or female, from gender identity, the psychological sense of being male or female, and from social gender role, the cultural norms that define feminine and masculine behavior. Orientation, in their account, is distinct from all three. By their reckoning, the core attractions that form the basis for adult sexual orientation typically emerge between middle childhood and early adolescence.

• 3. Beyond The Binary

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  Androphilia and gynephilia are terms drawn from behavioral science to describe attraction without fixing a sex or gender onto the person doing the attracting. Androphilia names attraction to masculinity. Gynephilia names attraction to femininity. The point is to identify the object of desire without making assumptions about the subject.

  Psychiatrist Anil Aggrawal explains why this is needed. It is difficult to decide whether a trans man attracted to males is a heterosexual female or a homosexual male, or whether a trans woman attracted to females is a heterosexual male or a lesbian. Any attempt to classify them, he writes, may cause confusion and arouse offense. Better, in such cases, to focus on the object of attraction rather than the sex of the subject.

  Sexologist Milton Diamond pushes the same idea about language. The terms heterosexual, homosexual, and bisexual, he writes, are better used as adjectives, not nouns, and better applied to behaviors, not people. These newer terms, he adds, do not carry the social weight of the former ones.

  Writing about the Samoan fa'afafine, sociologist Johanna Schmidt notes that in cultures recognizing a third gender, a label like homosexual transsexual simply does not align with the local categories. Bruce Bagemihl criticized how the labels heterosexual and homosexual get applied to transgender people, arguing the point of reference becomes solely the individual's genetic sex prior to reassignment. That, he wrote, ignores the person's own sense of gender identity. Other proposed terms reach for finer distinctions still, including gynandromorphophilia and gynemimetophilia for attraction to a person born male with a feminine gender expression.

• 4. The Case For Biology

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  No single controlling cause of sexual orientation has been identified, yet scientists favor biological models. There is considerably more evidence supporting nonsocial, biological causes than social ones, especially for males. Some researchers believe orientation is established at conception.

  Twin studies have pulled in different directions. A 2001 study appeared to exclude genes as a major factor. A 2010 study found homosexuality was explained by both genes and environmental factors. The experimental design of these studies has made them difficult to interpret. In 2012, a genome-wide linkage study of male sexual orientation found significant linkage with genes on chromosome Xq28 and on chromosome 8 in the pericentromeric region. It was the largest study of the genetic basis of homosexuality to that point, published online in November 2014. Then in August 2019, a genome-wide association study of 493,001 individuals concluded that hundreds or thousands of genetic variants underlie homosexual behavior, with 5 in particular significantly associated. That study found no excess signal on Xq28.

  The hormonal theory points elsewhere, to the womb. Just as hormones drive fetal sex differentiation, the theory holds, hormonal exposure shapes the orientation that emerges in the adult. The default developmental pathway for a human fetus is female. The Y chromosome induces the shift toward the male pathway, a process driven by androgens, mainly testosterone and dihydrotestosterone. The newly formed testicles secrete those androgens, which help differentiate the developing fetus, including its brain.

  What is striking is what the evidence rules out. There is no substantive evidence that parenting, early childhood experiences, or sexual abuse influence sexual orientation. Hypotheses about the post-natal social environment are weak, especially for males. The idea that homosexuality resulted from faulty psychological development, as the source puts it, has since been found to be based on prejudice and misinformation.

• 5. The Older Brother Effect

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  The probability of a male growing up to be gay increases with each older brother he has from the same mother. This is the fraternal birth order effect, and the numbers are concrete. The odds rise from roughly 2% for a first-born son to 4% for the second, 6% for the third, and onward, an increase of 38 to 48% with each successive male pregnancy. Scientists estimate that between 15% and 29% of gay men may owe their orientation to this effect.

  Ray Blanchard and Anthony Bogaert are credited with discovering the effect in the 1990s. The proposed mechanism is biological, not social, because the effect appears only with older biological brothers, not with step-brothers or adoptive brothers. It is called the maternal immunization hypothesis. Cells from a male fetus enter the mother's circulation during pregnancy carrying Y-proteins thought to play a role in masculinizing the brain. The mother's immune system builds antibodies to these proteins. Released on future male fetuses, those antibodies interfere with masculinization, leaving brain regions in a default female-typical arrangement.

  Biochemical support arrived in 2017. Researchers found that mothers of gay sons, especially those with older brothers, had significantly higher levels of antibodies to the NLGN4Y Y-protein than mothers of heterosexual sons. The effect carries odd caveats. It does not likely apply to first-born gay sons, and it is nullified if the man is left-handed. J. Michael Bailey and Jacques Balthazart argue the effect shows orientation is heavily influenced by prenatal biological mechanisms rather than unidentified factors in socialization.

• 6. Measuring The Continuum

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  Karl Heinrich Ulrichs proposed one of the earliest classification schemes in the 1860s, in pamphlets he published privately. Meant only to describe males, it sorted them into dionings, urnings, and uranodionings, categories that map onto the modern heterosexual, homosexual, and bisexual. An urning could be subdivided by degree of effeminacy, into a manly Mannling or an effeminate Weibling.

  Berlin sexologist Magnus Hirschfeld took the idea toward numbers. In 1896 he published a scheme measuring sexual desire on two independent 10-point scales, A for homosexual and B for heterosexual. A heterosexual person might be A0, B5. An asexual person would be A0, B0. Someone intensely attracted to both sexes would be A9, B9.

  Then came the Kinsey scale, the Heterosexual-Homosexual Rating Scale, first published in Sexual Behavior in the Human Male in 1948 by Alfred Kinsey, Wardell Pomeroy, and Clyde Martin. It ran from 0, exclusively heterosexual, to 6, exclusively homosexual, with the middle ratings capturing every blend in between. Masters and Johnson later found those middle ratings, 2 through 4, genuinely hard to assign for people with many experiences of both kinds.

  Critics had other complaints. Weinrich and colleagues argued the scale lumped together people who differed along separate dimensions. Kinsey collapsed overt experience and psychic reaction into one score, losing information. A third objection was that the scale treated heterosexuality and homosexuality as a tradeoff on one axis, when they might be better measured as two independent scales. Fritz Klein answered with the Klein Sexual Orientation Grid, introduced in his 1978 book The Bisexual Option, which assessed seven dimensions of sexuality at three points in life: past, present, and ideal. The Sell Assessment of Sexual Orientation went further still, with 12 questions measuring homosexuality and heterosexuality separately, and treating sexual attraction as the most important signal of all.

• 7. A Number That Bends

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  Assessing sexual attraction yields the greatest prevalence of homosexuality in a population, two to three times the proportion that reports same-sex behavior or a gay, lesbian, or bisexual identity. The number you get depends entirely on which question you ask. Laumann and colleagues, in 1994, found that among U.S. adults considered homosexual on one dimension, only 20% were homosexual on all three, while 70% qualified on just one.

  The numbers also bend across place and sex. The source records attraction rates as high as 21% among female adolescents in Norway and 17% among female adults in Australia, alongside far lower identity figures in the same populations. In Western cultures, surveys find on average that about 93% of men and 87% of women identify as completely heterosexual, with 2% of men and 0.5% of women identifying as completely homosexual.

  Diamond's longitudinal work shows the figures move within a single life. Over seven years, two-thirds of the women she followed changed their sexual identity at least once. One told her, I'm mainly straight but I'm one of those people who, if the right circumstance came along, would change my viewpoint.

  The stakes of the number are political, not merely academic. In the 1970s, Bruce Voeller, chair of the National Gay and Lesbian Task Force, popularized the claim that homosexuality runs at 10% of the population, reached by averaging a 13% figure for men and a 7% figure for women. He used it to convince politicians and the public that, in his words, we are everywhere. Knowing how much of a population is gay, the source notes, shapes whether that population is politically easy to ignore.

• 8. Invention Or Constant

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  Michel Foucault argued in The History of Sexuality, in 1976, that homosexuality as an identity did not exist in the eighteenth century. People then spoke of sodomy, which referred to acts rather than a kind of person. Sexuality, he wrote, is an invention of the modern state, the industrial revolution, and capitalism. That is the social constructionist case, and it has sharp opponents.

  The philosopher of science Michael Ruse holds that the constructionist approach rests on a selective reading of the historical record, one that confuses the existence of homosexual people with how they are labeled or treated. Other scholars argue for significant continuities between ancient and modern homosexuality. The disagreement is not abstract. In some cultures, sexuality is defined not by the sex of one's partner but by sexual role, whether one penetrates or is penetrated, with the passive role tied to femininity and the active to masculinity.

  An investigation of a small Brazilian fishing village found three categories for men: those who have sex only with men in a passive role, those who have sex only with women, and those who have sex with both in an active role. Only the consistently passive group was recognized by locals as distinct. Same-sex kissing between men, read as a sign of homosexuality in many English-speaking nations, is a common expression of friendship elsewhere.

  Professor Michael King draws out why any of this reaches a courtroom. The conclusion reached by scientists, he stated, is that sexual orientation is formed early in life and resistant to change, evidence that undermines suggestions that orientation is a choice. Law professor David Cruz, writing in 1999, complicated even that. Sexual orientation, he noted, might refer to a variety of different attributes, and it is not clear that one conception is most suited to all social, legal, and constitutional purposes.