Homosexuality

Abstract

Homosexuality, which the Medical Subject Headings thesaurus classifies under sexuality, is the pattern of sexual or romantic attraction to the same sex. Historically it has been the most intensively studied orientation — the marked category whose measurement, development, and biology drove the field — so cognitive psychology treats it not as a condition to be explained away but as a graded position on the same orientation instruments that locate every other pattern. This article reviews how homosexuality is defined and placed at the high pole of a graded orientation scale, the sex difference in category-specific genital arousal that distinguishes homosexual men from homosexual women, what developmental and genetic evidence does and does not establish about its origins, and why its measured prevalence and stability depend on whether attraction, behavior, or identity is the component counted.

Keywords: homosexuality, sexual orientation, Kinsey scale, category-specific arousal, Xq28

Introduction

Homosexuality is the pattern of sexual or romantic attraction to the same sex (Bailey et al., 2016). As a form of sexual orientation it occupies one pole of the orientation spectrum, and from the first systematic surveys onward it has been the pattern research actually set out to measure. Where heterosexuality is the unmarked default a culture treats as needing no account, homosexuality is the marked category — the one whose prevalence, origins, and stability were posed as questions, and around which the instruments of orientation research were largely built.

That history gives homosexuality a particular place in the cognitive psychology of orientation. The seven-point scale, the distinction between attraction, behavior, and identity, the physiological measures of arousal, and the genetic studies of the late twentieth century were all developed, in large part, to pin down same-sex attraction (Kinsey et al., 1948; Hamer et al., 1993). Cognitive psychology inherits those tools and applies them even-handedly: homosexuality is not a deviation from a norm but a graded position on the same scale as every other orientation, measured by the same dissociable components and read against the same evidence on arousal, development, and change (Chivers et al., 2010; Baumeister, 2000).

The Medical Subject Headings thesaurus indexes Homosexuality beneath Sexuality in its classification of behavior, and subdivides it in turn by sex. That placement is a retrieval convenience, not a theoretical claim about kinds of people; this article uses it only to situate homosexuality among related orientations and its own subtypes, and otherwise treats the psychology on its own terms.

Types of Homosexuality

Within the Medical Subject Headings thesaurus, Homosexuality is a heading indexed beneath Sexuality and subdivided into the two direct subtypes in Table 1, defined by the sex of the people involved. The distinction is not incidental to the psychology: the central sex difference in category-specific genital arousal, and the early genetic-linkage evidence, were found in men, while the strongest evidence on fluidity and erotic plasticity comes from women, so the two subtypes carry much of the measurement contrast this article develops. The categories are orthogonal to the dimensions of arousal, development, and fluidity discussed later: placing a person in one does not fix where they fall on those graded measures. The MeSH tree is a classification for literature retrieval, not a theory of how same-sex attraction is organized; it is used here only to name the subtypes a reader is likely to encounter.

Measuring Homosexuality

Homosexuality became a measurable idea the moment orientation was treated as graded rather than categorical. Kinsey, Pomeroy, and Martin (1948) placed people on a seven-point continuum from exclusively heterosexual (0) to exclusively homosexual (6), and homosexuality, in that scheme, is not a single point but the high region — ratings 5 and 6 — where predominantly and exclusively same-sex attraction fall. The scale made two things visible at once: that exclusive homosexuality is a minority pattern occupying the sparse end of the distribution, and that it is nonetheless the end of a continuum, so that a rating of 5 records a predominantly homosexual pattern with incidental other-pole response rather than an all-or-nothing state.

Being the marked, closely questioned pole makes the dissociation of components especially consequential here. Savin-Williams and Ream (2007) showed that attraction, behavior, and identity do not pick out exactly the same people, and the gap is widest away from the heterosexual anchor: some who report same-sex attraction have no same-sex behavior, some who behave have not adopted a same-sex identity, and the three counts of “how many people are homosexual” therefore differ. The measured prevalence of homosexuality is not one number but three, and which one is cited depends on whether attraction, behavior, or identity is the component counted.

Whether orientation needs one dimension or two bears directly on the same-sex pole. Lippa (2020) analyzed interest, personality, and sexual traits across orientation groups and asked whether variation is better captured by one bipolar hetero–homosexual axis or by two partly independent dimensions — other-sex and same-sex attraction considered separately. On the two-dimensional view, homosexuality is high same-sex attraction paired with low other-sex attraction, a positive profile to be measured in its own right rather than the mere mirror image of heterosexuality. Figure 1 shows where the pattern sits on the distribution the scale records.

The first demonstration makes the distribution interactive, letting the reader switch between attraction, behavior, and identity and watch how the measured size of the homosexual minority shifts with the component counted.

Arousal and the Sex Difference

The clearest window on homosexual arousal is the construct of category-specificity: the degree to which genital arousal is selective for one sex. Chivers and colleagues (2010) meta-analyzed studies recording both self-reported and genital arousal and found a large, reliable sex difference. In men, genital response is strongly category-specific and agrees closely with self-reported attraction: a homosexual man shows marked genital arousal to male stimuli and little to female stimuli, and his body and his report tell the same story. In women, including homosexual women, genital response is far less category-specific — substantial arousal is recorded to stimuli of both sexes regardless of stated orientation, and genital and self-reported arousal agree much less well.

This difference reframes what “homosexual arousal” even means, because it means something measurably different in the two sexes. Rieger, Chivers, and Bailey (2005), studying arousal patterns in bisexual men, relied on exactly the male category-specificity that makes genital arousal a usable index of orientation in men; the same method applied to women would be far less diagnostic. For homosexual men, then, the physiological measure and the self-report converge, and genital response can stand in for attraction. For homosexual women, the two measures come apart, and a category-specific genital reading cannot be assumed to track the orientation a woman reports. The sex difference is not a flaw in the instrument but a finding about how same-sex arousal is organized.

The consequence is methodological and it is large: a tool validated on homosexual men does not transfer unchanged to homosexual women. The second demonstration models the contrast directly, letting the reader switch the respondent's sex and watch category-specific genital arousal sharpen for men and flatten for women while self-reported same-sex attraction stays high for both.

Origins and Development

No question in orientation research has been posed more often than the origin of homosexuality, and the theories on offer are theories of orientation in general. Bem (1996) proposed the exotic-becomes-erotic (EBE) developmental theory as an account of both the majority and the minority pattern: childhood temperament channels a child toward sex-typical or sex-atypical activities, which determine which peers feel familiar and which feel different, and the sex experienced as exotic in childhood becomes the object of erotic attraction later. On this account homosexuality is the outcome when a child's preferences are sex-atypical, making the same sex the exotic one. Whatever its empirical standing, EBE is notable for deriving same-sex attraction from the same mechanism it uses for the heterosexual case rather than treating it as a special condition.

The biology has been studied just as intensively. Hamer and colleagues (1993) reported a linkage between DNA markers on the X chromosome — the region Xq28 — and male sexual orientation, an early and much-debated result that framed homosexuality as partly heritable rather than wholly chosen or wholly environmental. Three decades later, Ganna and colleagues (2019) analyzed the genetics of same-sex sexual behavior at the scale of hundreds of thousands of genomes and found no single gene and no simple pattern: many variants each contribute a tiny amount, the genetic influences are spread across the genome, and — crucially — they do not partition people into discrete heterosexual and homosexual kinds. The genetic architecture is polygenic and continuous, which means same-sex attraction is the high end of a graded distribution of the same underlying influences rather than the presence of a dedicated cause. The developmental and genetic pictures converge on one point: there is no special mechanism that produces homosexuality, only particular settings of the mechanisms that produce the whole range of orientation.

Prevalence, Stability, and Fluidity

How common homosexuality is depends, as the measurement section showed, on what is counted — and at the same-sex pole the components spread apart. Savin-Williams and Ream (2007) found that same-sex attraction, behavior, and identity each yield a different count, with attraction the most commonly reported and exclusive same-sex identity the least, so the prevalence of homosexuality is reported as a range rather than a single figure. The dissociation that makes the middle of the scale ambiguous is substantial here too: a person can report same-sex attraction without same-sex behavior or identity, and each combination is counted differently.

Stability is the second measurement theme, and it is sex-differentiated. Baumeister (2000) argued for erotic plasticity: the female sex drive is more responsive to social and situational circumstance than the male, which predicts that same-sex attraction and identity are, on average, held somewhat more flexibly by women than by men. Diamond (2008) followed women over ten years and documented movement in both directions — some women moved toward same-sex attraction and identity and some moved away — while finding that attractions, once established, showed real continuity. Same-sex attraction can therefore be both genuinely stable and, especially in women, open to change, with no contradiction between the two.

That change is one instance of a general capacity. Mock and Eibach (2012) reported over a ten-year adult span that most people's identity was stable, with change concentrated among those not exclusively heterosexual, and Diamond (2016) argued that sexual fluidity — situation-dependent change layered on an underlying orientation — is a general human capacity rather than a female peculiarity. For the measurement of homosexuality this means same-sex attraction is a stable but not immutable position on a continuum that admits movement. The third demonstration makes the pattern visible, letting the reader watch how the stability of an orientation component varies across the scale and differs by sex.

Worked Example

Consider two people assessed with the tools above. The first is a man who reports strong attraction to men, whose sexual history is with men, who identifies as gay, and who shows, in a laboratory, marked genital arousal to male stimuli and little to female stimuli. The second is a woman who reports strong attraction to women, whose history and identity are likewise same-sex, but who shows substantial genital arousal to stimuli of both sexes. Are both homosexual? On every component that defines orientation the answer for each is plainly yes — and the laboratory readings, which look so different, are exactly what the evidence predicts.

For the man, attraction, behavior, and identity place him at the exclusively homosexual anchor, and his genital arousal is category-specific, so the physiological measure converges with the other three (Chivers et al., 2010). For the woman, the same three components place her at the same anchor, but her genital arousal is non-specific — and that is precisely what female category-specificity predicts, so a non-specific reading is uninformative about her orientation rather than evidence against it (Rieger et al., 2005). The same non-specific reading means opposite things in the two cases only because male and female genital response are organized differently. Table 2 lays the measures side by side.

The example makes the article's point exact. Three components define orientation and agree in both people, so both are homosexual without qualification; the fourth measure converges for the man and is silent for the woman, not because they differ in orientation but because genital arousal is category-specific in men and weakly so in women. A model that did not carry that sex difference would misread the woman's non-specific arousal as ambiguity, when it is the expected and uninformative signal of a measure that does not apply to women the way it applies to men (Chivers et al., 2010).

Discussion

The cognitive psychology of homosexuality is the discipline of measuring same-sex attraction on the same graded instruments as any other orientation, rather than treating it as a condition apart. Located on the Kinsey continuum it is the high-rating region of a single scale (Kinsey et al., 1948); described two-dimensionally it is a positive profile of high same-sex and low other-sex attraction (Lippa, 2020); and it is subject to exactly the questions about arousal, development, and stability asked of the heterosexual majority.

Integrating the findings dissolves several apparent puzzles. The sex difference in category-specific arousal means same-sex arousal is organized differently in men and women, so a genital measure that indexes orientation in homosexual men is uninformative in homosexual women rather than contradictory (Chivers et al., 2010; Rieger et al., 2005). The developmental and genetic evidence explains same-sex attraction by particular settings of general mechanisms, not by a dedicated cause: the Xq28 linkage and the later genome-wide work point to a polygenic, continuous architecture with no single determinant (Bem, 1996; Hamer et al., 1993; Ganna et al., 2019). And homosexuality can be at once a stable orientation and open to change, because stability varies by component and by sex (Baumeister, 2000; Diamond, 2008; Mock & Eibach, 2012). The comprehensive review by Bailey and colleagues (2016) reaches the same integrative conclusion: orientation is real, early-emerging, and substantially stable across its range, and homosexuality is the high-frequency region of the same-sex end of that range rather than a separate kind of thing. As a monosexual pattern — attraction directed at a single sex — exclusive homosexuality is measured on exactly the instruments that locate its exclusive-heterosexual counterpart, the two differing in frequency and direction, not in the kind of measurement they require.

None of this reduces homosexuality to any single measure. The point of the cognitive analysis is the opposite: by specifying which component is in view and how it is assessed, it explains why the most-studied orientation yields a prevalence that is a range, an arousal signature that differs by sex, and a stability that is real without being absolute.

Current Directions

The most consequential recent movement is the replacement of the categorical picture of orientation with a genuinely dimensional one, and the genetics of homosexuality are where that shift has been most decisive. Ganna and colleagues (2019) established that the genetics of same-sex behavior are polygenic and continuous, with no variant that sorts people into discrete groups — a finding that retired the search for a single “gay gene” that Hamer and colleagues (1993) had seemed to open with the Xq28 linkage a generation earlier. Same-sex attraction, on the current picture, is the high end of a smooth distribution of many small influences, not a population defined by the presence of one gene. The study makes explicit that this dissolves the categorical boundary in both directions: there is no genetic line around homosexuality any more than around heterosexuality.

That reframing turns the measurement themes of this article into an active research agenda. If orientation is dimensional (Lippa, 2020), then same-sex attraction deserves the two-dimensional, component-specific measurement that distinguishes it as a positive profile rather than scoring it as the absence of heterosexuality. If erotic plasticity and fluidity are real and sex-differentiated (Baumeister, 2000; Diamond, 2016), then the stability of same-sex attraction is a quantity to be estimated separately for women and men. And the robust sex difference in category-specific arousal (Chivers et al., 2010) leaves open a basic question the field is still pursuing: why same-sex genital arousal is so sharply selective in homosexual men and so diffusely non-selective in homosexual women, and what that implies for every instrument built to measure orientation from the body.

Common Misconceptions

“Homosexuality is a single thing with a single cause.”

A genome-wide study of hundreds of thousands of people found same-sex behavior to be polygenic and continuous, with no single gene and no genetic boundary; the earlier Xq28 linkage, even taken at face value, described a contribution to male orientation, not a determinant (Hamer et al., 1993; Ganna et al., 2019).

“A woman who is aroused by both sexes in the lab cannot really be lesbian.”

In women, genital arousal is only weakly category-specific, so non-specific arousal is the expected reading for homosexual women and is uninformative about orientation; the category-specific inference holds only for men (Chivers et al., 2010).

“Everyone is either exclusively homosexual or exclusively heterosexual.”

The Kinsey scale is a seven-point continuum; homosexuality occupies its high region (ratings 5–6), and ratings between the poles record graded and mixed patterns rather than a forced choice between two categories (Kinsey et al., 1948).

“There is one true number for how common homosexuality is.”

Prevalence depends on the component counted: same-sex attraction, behavior, and identity yield different figures, because the components dissociate and a person can report one without the others (Savin-Williams & Ream, 2007).

Glossary

Attraction.

The felt pull of sexual or romantic interest toward a sex; the component of orientation that defines homosexuality and the one on which it is most commonly reported.

Category-specificity.

The degree to which genital arousal is selective for one sex; strong in homosexual men, weak in homosexual women, and the central sex difference in how same-sex arousal is read.

Component (of orientation).

One of the separable aspects of orientation — attraction, arousal, fantasy, behavior, or identity — that are correlated but can give different answers for one person.

Concordance (of components).

The degree to which a person's separable orientation components agree; at the same-sex pole concordance is substantial but lower than at the heterosexual anchor.

Erotic plasticity.

The responsiveness of the sex drive to social and situational circumstance; proposed to be greater in women than men, which predicts that same-sex attraction and identity are held somewhat more flexibly by women.

Exotic-becomes-erotic (EBE) theory.

Bem's developmental account in which childhood temperament determines which sex feels familiar and which exotic, and the exotic sex later becomes the object of attraction; it derives the homosexual outcome from sex-atypical temperament.

Homosexuality.

The pattern of sexual or romantic attraction to the same sex; in cognitive psychology, the high region of the orientation scale rather than a condition set apart from it.

Kinsey scale.

A seven-point continuum from exclusively heterosexual (0) to exclusively homosexual (6); homosexuality occupies its high region, ratings 5 and 6.

Monosexual.

Attracted to a single sex; exclusive homosexuality is the low-frequency monosexual pattern, exclusive heterosexuality the high-frequency one.

Polygenic.

Influenced by many genes of individually small effect; the genome-wide architecture found for same-sex behavior, which rules out a single determining gene.

Prevalence.

The share of a population with a given orientation; for homosexuality it is a minority on every component, and its exact size differs by whether attraction, behavior, or identity is counted.

Sexual fluidity.

Situation- and relationship-dependent change in attraction or identity layered on an underlying orientation; a general capacity that applies to same-sex attraction, more pronounced in women.

Sexuality.

The multidimensional construct — attraction, arousal, fantasy, behavior, and identity — under which MeSH classifies homosexuality and its sibling orientations.

Stability.

The tendency of an orientation component to persist across time; same-sex attraction is, on longitudinal evidence, genuinely stable yet on average less fixed than exclusive heterosexual attraction, especially in women.

Xq28.

A region at the tip of the long arm of the X chromosome reported in 1993 to show linkage with male sexual orientation; an early, much-debated result later subsumed by polygenic findings.

Key Researchers

J. Michael Bailey

is a professor of psychology at Northwestern University whose comprehensive review synthesized the measurement, development, and biology of sexual orientation across the heterosexual–homosexual range.

Faculty page - Google Scholar - Wikipedia

Roy F. Baumeister

is a social psychologist, professor emeritus at Florida State University and at the University of Queensland, whose concept of erotic plasticity holds that the female sex drive is more socially flexible than the male, predicting that female same-sex identity is held less rigidly than male.

ORCID - Google Scholar - Wikipedia

Daryl J. Bem

is a professor emeritus of psychology at Cornell University whose exotic-becomes-erotic theory offers a single developmental account of how both the minority homosexual pattern and the majority heterosexual one arise from early temperament.

Faculty page - Wikipedia

Meredith L. Chivers

is a professor of psychology at Queen's University whose research established that genital arousal is strongly category-specific in homosexual men but far less so in women regardless of orientation.

ORCID - Faculty page - Wikipedia

Lisa M. Diamond

is a distinguished professor of psychology and gender studies at the University of Utah whose decade-long longitudinal research established sexual fluidity, documenting movement both toward and away from same-sex attraction and identity.

Faculty page - Wikipedia

Dean H. Hamer

is an American geneticist, emeritus at the U.S. National Cancer Institute, whose 1993 study reported a linkage between DNA markers on the X chromosome (Xq28) and male sexual orientation — the most-cited early genetic study of homosexuality.

Wikipedia

Alfred C. Kinsey

(1894–1956) founded the Institute for Sex Research at Indiana University and devised the graded scale of orientation on which exclusive homosexuality occupies the high pole (rating 6).

Wikipedia

Richard A. Lippa

is a professor emeritus of psychology at California State University, Fullerton whose analyses asked whether two independent dimensions, rather than a single hetero–homosexual axis, best represent variation in orientation, treating homosexuality as a positive profile.

Faculty page

Ritch C. Savin-Williams

is a professor emeritus of developmental psychology at Cornell University whose research on the prevalence and stability of orientation components established how same-sex attraction, behavior, and identity emerge and diverge in youth.

ORCID - Faculty page - Google Scholar

Frequently Asked Questions

What is homosexuality?

In research, homosexuality is the pattern of sexual or romantic attraction to the same sex. Cognitive psychology treats it as the high region of the orientation spectrum rather than as a condition set apart, and studies it on the same graded instruments used for every other orientation (Bailey et al., 2016).

Where does homosexuality fall on the Kinsey scale?

At the high end: ratings 5 (predominantly homosexual, with incidental other-pole response) and 6 (exclusively homosexual), which together hold a small share of the distribution (Kinsey et al., 1948). Homosexuality is a graded region of the scale, not a single point.

How common is homosexuality?

There is no single figure. Same-sex attraction, behavior, and identity each give a different count, with attraction the most commonly reported and exclusive same-sex identity the least, because the components dissociate and a person can report one without the others (Savin-Williams & Ream, 2007).

Is homosexual arousal the same in men and women?

No. Genital arousal is strongly category-specific in homosexual men, tracking the sex they are attracted to, but only weakly category-specific in homosexual women, who show substantial genital response to stimuli of both sexes regardless of stated orientation (Chivers et al., 2010). It is the central sex difference in how same-sex arousal is measured.

What determines whether someone is homosexual?

No single cause. Developmental accounts such as the exotic-becomes-erotic theory derive same-sex attraction from early temperament (Bem, 1996), and genome-wide evidence shows orientation to be polygenic and continuous, with no single gene and no genetic boundary around homosexuality (Hamer et al., 1993; Ganna et al., 2019).

Is there a “gay gene”?

No. An early study reported linkage between a region of the X chromosome (Xq28) and male orientation (Hamer et al., 1993), but a genome-wide analysis of hundreds of thousands of people later found same-sex behavior to be influenced by many genes of tiny effect, with no single determining gene (Ganna et al., 2019).

Is homosexual orientation stable over time?

Same-sex attraction is genuinely stable for most people, and most adults' identity does not change (Savin-Williams & Ream, 2007; Mock & Eibach, 2012). It is, on average, somewhat less fixed than exclusive heterosexual attraction, and more open to change in women than in men (Baumeister, 2000; Diamond, 2008).

Why was homosexuality studied so much more than heterosexuality?

Because it was the marked category — the pattern whose prevalence, origins, and stability were posed as open questions, while the heterosexual majority was treated as needing no account. Many of the field's core instruments were built to measure same-sex attraction, and cognitive psychology now applies them even-handedly across the whole scale (Lippa, 2020).

References