Sexual Orientation
This is chapter 1.2 of Autoheterosexual: Attracted to Being the Other Sex. It explains the basics of sexual orientation.
Many animals have something inside them that compels them to mate with others of their species. This inner drive motivates them to get closer to the object of their affection, court them, and make sexual contact with them.
This motivating force is sexual orientation, and it plays a key role in uniting sperm and egg. Without it, the two might never find each other. The most common sexual orientations are allosexual orientations, meaning they involve attraction to others (“allo” means “other”).
The American Psychological Association has defined sexual orientation as “one’s enduring sexual attraction to male partners, female partners, or both”[i]. Likewise, some sexologists have defined it as “relative sexual attraction to men, to women, or to both”[ii].
This is the mainstream definition of sexual orientation. When asked about their sexual orientation, most people talk about their attraction to men or women.
The DSM-5 and DSM-5-TR both classify this pattern of attraction as “normophilic”, defining it as “sexual interest in genital stimulation or preparatory fondling with phenotypically normal, physically mature, consenting human partners”[iii]. It’s what most people call “normal”, or “vanilla”.
But the vast majority of existing sexual orientations are a flavor other than vanilla. When these nonvanilla sexual orientations rival or outshine someone’s vanilla side, they fall under the heading of paraphilia[iv]. “Para-” is a Greek root with many meanings, some of which are “alongside of”, “beside”, “near”, “resembling”, “beyond”, and “apart from”.
These sexual interests are sometimes described as “kinks” or “fetishes”, but I won’t be using those terms here. Designating a sexual interest as a “kink” or “fetish” makes it seem lesser—less important, less worthy of respect, and less significant overall. This limited erotic framing also underemphasizes the pivotal role that sexuality plays in our emotional lives.
For most people, the object of their affection is an adult human of the other sex. This often leads to love, marriage, and kids, and keeps our species going by starting the cycle anew. But who can say that people with other sexual interests aren’t equally justified in pursuing their form of love, provided it doesn’t harm others?
Describing the most common forms of love as “sexual orientations” and less common forms of love as “paraphilias” elevates certain sexualities over others in a way that doesn’t necessarily apply to our individual lives. When deciding who we are as sexual beings and how we want to structure our lives to accommodate our sexualities, the relative strengths of our various sexual interests often matter more than how common they are.
Therefore, I will use everyday language that makes the same fundamental distinction between “normal” sexuality and all that falls outside of it. Sexuality based on attraction to women, men, or both will be vanilla, and everything else will be nonvanilla.
I’ll also use broad terms that apply no matter what someone is into:
Sexual interest—a sexually motivated interest in a particular type of entity, embodiment, or method of interaction
Sexual orientation—an enduring pattern of preferential sexual or romantic interest in a particular type of entity, embodiment, or method of interaction.
People can be sexually oriented towards other beings based on sex, gender, race, age, health, species, or other attributes. Some are even attracted to nonliving objects[v]. Although some of these types of attraction are uncommon, they are why I use the broad term “entity” in this definition of sexual orientation.
I’m not alone in thinking that the definition of sexual orientation could be broadened. Sexologist Michael Seto proposed a broader conception of sexual orientation, which he defined as “a stable tendency to preferentially orient—in terms of attention, interest, attraction, and genital arousal—to particular classes of sexual stimuli”[vi].
These broader definitions of sexual orientation include the elements of preference (preferring one thing over other things), persistence (stability over time), and an erotic target (the type of thing that draws a person’s sexual interest).
In short, sexual orientation is a stable sexual preference for particular types of things.
Measuring Sexual Orientation
There is no one perfect way to measure sexual orientation.
If a sexologist is trying to measure someone’s sexual preferences, they have two main approaches: they can either ask questions or see how bodies react to stimuli[vii].
When conducting such research, they measure up to four aspects of sexual orientation:
What a person is attracted to (sexual attraction)
How they see themselves sexually (sexual identity)
How they behave sexually (sexual behavior)
Whether there are signs of physical arousal after exposure to erotic stimuli (physiologic arousal)
The first three are measured by asking questions. The last one requires a lab setup, trained technicians, and a lot of man-hours. This is why sexologists usually just ask questions—it’s easier, cheaper, and faster.
But relying on self-reports depends on people knowing themselves well and having nothing to hide. A lot of people are uncomfortable with sex in general, so this approach has obvious flaws.
Some people have a tendency to say what they think will portray themselves in a flattering light. This social desirability bias can affect how they report on their experience and make the data less accurate than it would otherwise be.
Measuring how people’s bodies respond to erotic pictures and videos is important because it’s less affected by how well they know themselves or how they want to portray themselves.
Consider the hypothetical situation of a man who arrives at a sexual research facility to get his arousal patterns tested. He says he is only attracted to women, has only been with them, and is heterosexual. But when his genital arousal is measured, his strongest response is to porn depicting men, and he barely responds to porn depicting women.
Based on his self-reported sexual behavior, sexual attraction, and sexual identity, he’s straight. But based on his physical arousal pattern, he’s gay.
What would you say his sexual orientation is? Is he a straight man who just happens to get most strongly aroused from looking at men, or is he actually gay?
I think he’s gay, and I suspect this interpretation is common. People often interpret physical arousal as a fairly clear-cut sign of what someone is into. (By the way, this hypothetical scenario wasn’t actually hypothetical: it happens sometimes[viii]).
This shows one of the pitfalls of relying solely on self-reports when measuring sexual orientation: The way we portray ourselves doesn’t always match reality. Sometimes we are wrong about ourselves.
Sexual Orientation and Hormonal Exposure
Genes and hormone exposure in utero both affect the vanilla sexual orientation that people are likely to have.
The most compelling explanation, the organizational hypothesis[ix], is that hormonal exposure during critical developmental periods influences the sexual differentiation process.
During human fetal development, males and females experience different levels of testosterone[x]. Males have testes that release testosterone, promoting growth of male genitalia. Females lack testes, so they’re exposed to much less testosterone and usually develop female-typical genitalia as a result.
Females and males have different average psychologies[xi]. Since hormones influence the sexual differentiation process, hormonal exposure in the womb can shift people’s gendered psychology in male-typical or female-typical directions. This shift includes sexual orientation, which is why males tend to be masculine and attracted to women, while females tend to be feminine and attracted to men.
Since sexual orientation and gendered psychological traits tend to develop in tandem, homosexuality is associated with a cross-gender shift in mental traits[xii]. On average, homosexual males are more feminine than heterosexual males, and homosexual females are more masculine than heterosexual females[xiii].
The cross-gender psychological shift associated with homosexuality shows up in childhood behavior, self-rated masculinity and femininity, occupation preferences, and many mental traits[xiv]. It even shows up in brain structure[xv].
The influence of hormones seems to extend to nonvanilla sexualities as well. Most nonvanilla sexual interests are consistently found more often in males[xvi], which suggests that masculinization is associated with the development of nonvanilla sexual orientations such as autoheterosexuality.
Easier to Differentiate the Two Types of MTFs
By combining these observations that attractions to women and nonvanilla sexualities both seem to be associated with masculinization, it’s possible to infer that it can be harder to tell apart the two types of FTMs than the two types of MTFs.
To show what I mean, I’ll put a “+” or “-” symbol in parentheses beside traits to indicate positive or negative associations with masculinization:
Homosexual females are attracted to women (+)
Autoandrophilic females have an attraction to men (-) that is autosexual and therefore nonvanilla (+)
From these associations, we can expect that autoandrophilic females will tend to have an intermediate degree of masculinization which exceeds that of heterosexual females yet falls short of homosexual females.
The situation in males is more straightforward:
Homosexual males are attracted to men (-)
Autogynephilic males have an attraction to women (+) that is autosexual and therefore nonvanilla (+)
It follows that we can expect autogynephilic males to usually be about as masculine as typical heterosexual males, or even a bit more so. By contrast, we can expect homosexual males to usually be noticeably more feminine in comparison.
Combining these observations, it seems that the sexualities underlying both types of MTF transgenderism differ far more in terms of associated masculinization than do the sexualities underlying both types of FTM transgenderism. Therefore, it will generally be easier to tell apart the two types of MTFs than the two types of FTMs.
Fraternal Birth Order Effect
In addition to genes and hormones, male homosexuality is also affected by birth order. The more older brothers a male has, the more likely that male is to be gay—a phenomenon known as the fraternal birth order effect (FBOE).
The FBOE is also particularly associated with gender-atypical homosexuality: feminine homosexual males tend to have more older brothers than masculine homosexual males[xvii].
The leading explanation for this effect relates to mothers’ immune systems[xviii]. As females, their immune systems are likely to recognize male-related proteins as “other” and form an immune response to them. With each successive male fetus, this immune response grows stronger, which could inhibit one or more male-related proteins involved in male sexual development. The result could be under-masculinization of a male fetus, leading to androphilia and a cross-sex shift in mental traits.
Some scientists hypothesize that a male-related protein called NLGN4Y plays a role. One study found that mothers of homosexual males had more antibodies against this protein than mothers of heterosexual males, and both groups of mothers had more antibodies than mothers without sons[xix].
Scientists have estimated that 15–29% of cases of male homosexuality can be attributed to the FBOE[xx]. However, research also indicates there’s a second type of maternal immune response that contributes to homosexuality in both sexes[xxi], which suggests the true proportion of homosexual males who owe their orientations to maternal immune factors is likely even higher[xxii].
These influences of birth order might also influence female homosexuality. Researchers have found evidence suggesting that homosexuality in both sexes is influenced by birth order[xxiii], and that although older brothers raise the odds of homosexuality more than older sisters, older siblings of either sex increase the odds of homosexuality among later-born siblings.
The “Where” and “What” of Sexual Orientation
Autosexual orientations cause attractions to being.
Since autosexual orientations create attractions to being particular types of things, these orientations can also be thought of as attractions to various types of embodiment (e.g., being a particular gender, race, age, or species).
It’s theorized that autosexual orientations result when someone’s sexuality gets directed towards the self (auto) instead of others (allo). It’s a difference of location, not type. The “where” is different, not the “what”[xxiv].
The “what” (woman, man, minor, animal, etc.) is known as an erotic target. The “where” is that erotic target’s location.
The formal names for sexual orientations usually use Greek roots to describe the where and what of love by utilizing a “location-type-love” naming structure:
Location (“allo-”, “auto-”, “ambi-”)
Erotic target, or type (“gyne”, “andro”, “pedo”, “zoo”, etc.)
Love (“-philia”)
I’ll demonstrate how these location prefixes work with gynephilia, a love of women.
A love of others as women is allogynephilia. However, attractions to others are so common that “allo” is often left out for brevity.
A love of self as a woman is autogynephilia.
A love of both self and others as women is ambigynephilia. Ambigynephilia is co-occurring allogynephilia and autogynephilia.
Autosexual Trans Identities
Autosexual orientations are the most common cause of cross-identities (identities that are incongruent with one’s default physical form). These are usually called trans identities. “Trans” means “across” or “on the other side of”.
Cross-gender identity is the most common type of trans identity, but other types exist, too. Autosexual cross-identities take this general form:
For any dimension of sexual attraction X, autosexual attraction to embodying X can lead to X euphoria, X dysphoria, or a trans-X identity.
I’ll use the sexual dimension of race as an example.
Someone with autosexual attraction to being a particular race can have positive feelings (race euphoria) in response to perceptions of embodying that race. They can also have negative feelings (race dysphoria) when they perceive a shortcoming in their racial embodiment. Working in tandem, these positive and negative race-based feelings influence the development of a transrace identity.
People who are autosexual in one dimension of their sexuality are often autosexual in other dimensions of their sexuality. This is why people with rarer types of trans identity are far more likely to be transgender than those who don’t have any trans identities at all.
For example, there are people who identify as dragons, werewolves, monsters, or other mythical nonhuman entities. People who identify in this way are otherkin. These identities are transspecies in nature because they cross in the dimension of species.
Roughly a third of otherkin are transgender. In a sexual context, otherkin usually enjoy being treated as the same type of entity they identify as. They are also likely to be that same type of entity in their sexual fantasies.
This high rate of transgenderism in otherkin and the common underlying interest in erotic cross-embodiment suggests that autosexuality underlies both transgender and transspecies identity.
In Sum:
Sexual orientation is a motivational system that drives sexual behavior. It originated as a way to unite sperm and egg. People are usually sexually attracted to adult humans of the other sex, but the specific love object can be just about any type of entity.
In the womb, both genes and hormones influence the development of mental traits and vanilla sexual orientations. Psychological traits and orientations tend to move together in tandem, so homosexuality is associated with a cross-gender shift in mental traits.
Some cases of male homosexuality can be attributed to the fraternal birth order effect—the finding that the greater the number of older brothers a male has, the more likely that male is to be gay. Feminine gay males tend to have more older brothers than masculine gay males, which suggests that this cause of male homosexuality may be especially responsible for the kind of gender-atypical male homosexuality that can lead to transgenderism. Some research suggests that birth order also affects the development of homosexuality in females.
Sexologists usually measure sexual orientation by asking questions about sexual identity, sexual behavior, or sexual attraction. Some sexologists measure physical arousal in the lab to collect data that’s less biased by shortcomings of self-knowledge (or the common human tendency to present oneself in a flattering light).
Sexual orientation is a motivational system that drives sexual behavior. It originated as a way to unite sperm and egg. People are usually sexually attracted to adult humans of the other sex, but the specific object of attraction can be just about any type of entity.
In the womb, both genes and hormones influence the development of mental traits and vanilla sexual orientations. Psychological traits and orientations tend to move together in tandem, so homosexuality is associated with a cross-gender shift in mental traits.
Formal names for sexual attractions have a “where-what-love” naming structure that describes the “where” and “what” of love. They list the location first (self or other), followed by erotic target (woman, man, child, wolf, etc.), and end with love (philia). Attraction to others is so common that the location is often left unmentioned (e.g., “androphilia” instead of “alloandrophilia”).
Autosexual orientations are the most common cause of cross-identities (trans identities). Depending on whether sexual attraction is in the dimension of gender, age, race, or species, it will lead to a different type of trans identity. For any dimension of attraction X, autosexual attraction to embodying X can lead to X euphoria, X dysphoria, or a cross-X identity.
[i] VandenBos, APA Dictionary of Psychology (2nd Ed.)., 974.
[ii] Bailey et al., “Sexual Orientation, Controversy, and Science,” 45.
[iii] American Psychiatric Association and American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, 685; “Diagnostic and Statistical Manual of Mental Disorders : Fifth Edition Text Revision DSM-5-TRTM,” 779.
[iv] American Psychiatric Association and American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, 685.
[v] Marsh, “Love among the Objectum Sexuals.”
[vi] Seto, “The Puzzle of Male Chronophilias,” 1.
[vii] Bailey et al., “Sexual Orientation, Controversy, and Science,” 48,49.
[viii] Bailey, “Reply to Feinstein and Galupo and to Zivony.”
[ix] Bailey et al., “Sexual Orientation, Controversy, and Science,” 69–72.
[x] Bailey et al., 70.
[xi] Del Giudice, Booth, and Irwing, “The Distance Between Mars and Venus”; Kajonius and Johnson, “Sex Differences in 30 Facets of the Five Factor Model of Personality in the Large Public (N = 320,128)”; Eagly and Revelle, “Understanding the Magnitude of Psychological Differences Between Women and Men Requires Seeing the Forest and the Trees.”
[xii] LeVay, Gay, Straight, and the Reason Why, 164.
[xiii] Lippa, “Interest, Personality, and Sexual Traits That Distinguish Heterosexual, Bisexual, and Homosexual Individuals”; Lippa, “Sex Differences and Sexual Orientation Differences in Personality”; Lippa, “Sexual Orientation and Personality.”
[xiv] Bailey and Zucker, “Childhood Sex-Typed Behavior and Sexual Orientation: A Conceptual Analysis and Quantitative Review”; Allen and Robson, “Personality and Sexual Orientation”; Lippa, “Sex Differences and Sexual Orientation Differences in Personality”; Lippa, “Sexual Orientation and Personality”; Peters, Manning, and Reimers, “The Effects of Sex, Sexual Orientation, and Digit Ratio (2D.”
[xv] Savic and Lindström, “PET and MRI Show Differences in Cerebral Asymmetry and Functional Connectivity between Homo- and Heterosexual Subjects.”
[xvi] Bártová et al., “The Prevalence of Paraphilic Interests in the Czech Population”; Dawson, Bannerman, and Lalumière, “Paraphilic Interests,” 12; Baur et al., “Paraphilic Sexual Interests and Sexually Coercive Behavior,” 4.
[xvii] Blanchard, “Fraternal Birth Order, Family Size, and Male Homosexuality,” 10.
[xviii] VanderLaan et al., “Birth Weight and Two Possible Types of Maternal Effects on Male Sexual Orientation,” 26.
[xix] Bogaert et al., “Male Homosexuality and Maternal Immune Responsivity to the Y-Linked Protein NLGN4Y.”
[xx] Blanchard and Bogaert, “Proportion of Homosexual Men Who Owe Their Sexual Orientation to Fraternal Birth Order”; Cantor and Bogaert, “How Many Gay Men Owe Their Sexual Orientation to Fraternal Birth Order?”
[xxi] Blanchard, “Fertility in the Mothers of Firstborn Homosexual and Heterosexual Men,” 555.
[xxii] Blanchard, “A Possible Second Type of Maternal–Fetal Immune Interaction Involved in Both Male and Female Homosexuality,” 1510.
[xxiii] Ablaza, Kabátek, and Perales, “Are Sibship Characteristics Predictive of Same Sex Marriage?”
[xxiv] Freund and Blanchard, “Erotic Target Location Errors in Male Gender Dysphorics, Paedophiles, and Fetishists,” 562.