Malvina N. Skorska

Facial Structure Predicts Sexual Orientation in Both Men and Women.

Biological models have typically framed sexual orientation in terms of effects of variation in fetal androgen signaling on sexual differentiation, although other biological models exist. Despite marked sex differences in facial structure, the relationship between sexual orientation and facial structure is understudied. A total of 52 lesbian women, 134 heterosexual women, 77 gay men, and 127 heterosexual men were recruited at a Canadian campus and various Canadian Pride and sexuality events. We found that facial structure differed depending on sexual orientation; substantial variation in sexual orientation was predicted using facial metrics computed by a facial modelling program from photographs of White faces. At the univariate level, lesbian and heterosexual women differed in 17 facial features (out of 63) and four were unique multivariate predictors in logistic regression. Gay and heterosexual men differed in 11 facial features at the univariate level, of which three were unique multivariate predictors. Some, but not all, of the facial metrics differed between the sexes. Lesbian women had noses that were more turned up (also more turned up in heterosexual men), mouths that were more puckered, smaller foreheads, and marginally more masculine face shapes (also in heterosexual men) than heterosexual women. Gay men had more convex cheeks, shorter noses (also in heterosexual women), and foreheads that were more tilted back relative to heterosexual men. Principal components analysis and discriminant functions analysis generally corroborated these results. The mechanisms underlying variation in craniofacial structure—both related and unrelated to sexual differentiation—may thus be important in understanding the development of sexual orientation.

Male homosexuality and maternal immune responsivity to the Y-linked protein NLGN4Y

Significance Gay men have, on average, a greater number of older brothers than do heterosexual men, a well-known finding within sexual science. This finding has been termed the fraternal birth order effect. Strong scientific interest in sexual orientation exists because it is a fundamental human characteristic, and because its origins are often the focal point of considerable social controversy. Our study is a major advance in understanding the origins of sexual orientation in men by providing support for a theorized but previously unexamined biological mechanism—a maternal immune response to a protein important in male fetal brain development—and by beginning to explain one of the most reliable correlates of male homosexuality: older brothers. We conducted a direct test of an immunological explanation of the finding that gay men have a greater number of older brothers than do heterosexual men. This explanation posits that some mothers develop antibodies against a Y-linked protein important in male brain development, and that this effect becomes increasingly likely with each male gestation, altering brain structures underlying sexual orientation in their later-born sons. Immune assays targeting two Y-linked proteins important in brain development—protocadherin 11 Y-linked (PCDH11Y) and neuroligin 4 Y-linked (NLGN4Y; isoforms 1 and 2)—were developed. Plasma from mothers of sons, about half of whom had a gay son, along with additional controls (women with no sons, men) was analyzed for male protein-specific antibodies. Results indicated women had significantly higher anti-NLGN4Y levels than men. In addition, after statistically controlling for number of pregnancies, mothers of gay sons, particularly those with older brothers, had significantly higher anti-NLGN4Y levels than did the control samples of women, including mothers of heterosexual sons. The results suggest an association between a maternal immune response to NLGN4Y and subsequent sexual orientation in male offspring.

Tapping generalized essentialism to predict outgroup prejudices.

Psychological essentialism, the perception that groups possess inherent properties binding them and differentiating them from others, is theoretically relevant to predicting prejudice. Recent developments isolate two key dimensions: essentialistic entitativity (EE; groups as unitary, whole, entity-like) and essentialistic naturalness (EN; groups as fixed and immutable). We introduce a novel question: does tapping the covariance between EE and EN, rather than pitting them against each other, boost prejudice prediction? In Study 1 (re-analysis of Roets & Van Hiel, 2011b, Samples 1-3, in Belgium) and Study 2 (new Canadian data) their common/shared variance, modelled as generalized essentialism, doubles the predictive power relative to regression-based approaches with regard to racism (but not anti-gay or -schizophrenic prejudices). Theoretical implications are discussed.

Handedness, sexual orientation, and somatic markers for prenatal androgens: Are southpaws really that gay?

ABSTRACT Background: Some evidence suggests that prenatal androgens influence both handedness and sexual orientation. This study sought to clarify how androgens, handedness, and sexual orientation are interrelated. Methods: Data were obtained from large samples of students enrolled at universities in Malaysia and the US, including self-reported information on handedness, sexual orientation, and five somatic markers of prenatal androgen exposure (2D:4D, height, strength, muscularity, and athletic ability). Factor analysis of these somatic markers yielded two factors: a muscular coordination and a bone growth factor. Results: In women, but not in men, ambidextrousness was more prevalent among those with homosexual tendencies. Modest and often complex associations were found between the androgen factors and handedness. Clear links between the androgen factors and sexual orientation were found, especially for muscular coordination. For males and females, intermediate sex-typical androgen exposure was associated with heterosexual preferences. Conclusions: Ambidextrousness appears to be somewhat more common among females with homosexual tendencies, but left-handedness is nearly as strongly associated with heterosexual preferences, particularly in males, as is right-handedness. Factors indicative of prenatal androgen exposure are associated with sexual orientation in theoretically predictable ways, especially for muscular coordination, but associations between prenatal androgens and handedness are complex.

Sexual Orientation, Objective Height, and Self-Reported Height

Studies that have used mostly self-reported height have found that androphilic men and women are shorter than gynephilic men and women, respectively. This study examined whether an objective height difference exists or whether a psychosocial account (e.g., distortion of self-reports) may explain these putative height differences. A total of 863 participants, recruited at a Canadian university, the surrounding region, and through lesbian, gay, bisexual, and transgender (LGBT) events across Canada, self-reported their height and had their height measured. Androphilic men were shorter, on average, than gynephilic men. There was no objective height difference between gynephilic, ambiphilic, and androphilic women. Self-reported height, statistically controlling for objective height, was not related to sexual orientation. These findings are the first to show an objective height difference between androphilic and gynephilic men. Also, the findings suggest that previous studies using self-reported height found part of a true objective height difference between androphilic and gynephilic men. These findings have implications for existing biological theories of men’s sexual orientation development.

Pubertal onset and anal sex role among gay men.

Developmental theories of sexual orientation largely center on sexual differentiation processes. One hypothesis is that low prenatal androgens are associated with same-sex attraction in men. Using indirect measures of androgens (e.g., height, weight, pubertal onset), this hypothesis has received mixed support, suggesting there may be subgroups of gay men who differ in their developmental biology. Here we assessed whether subgroups of gay men (n = 312) based on anal sex role (ASR) preference and behavior differ in pubertal onset, weight, height, and/or body hair compared with heterosexual men (n = 127). Gay men with a top ASR had an earlier pubertal onset, were taller, and had more body hair compared with other gay men (bottom ASR, versatile ASR) and heterosexual men. Also, gay men with a bottom ASR were intermediate in their pubertal onset between gay men with a top ASR and heterosexual men, and they reported less body hair compared with these same groups. These results are consistent with the hypothesis that there are subgroups of gay men who differ in aspects of biological development that contribute to their sexual orientation. Furthermore, our results indicate earlier pubertal onset in gay men is associated with increased masculine somatic traits.

Prenatal Androgens in Men’s Sexual Orientation: Evidence for a More Nuanced Role?

Breedlove (2017) provides a thoughtful review of prenatal hormone theory (Ellis&Ames1987) and thedevelopment of sexual orientation.Specifically,Breedlovearguesthatprenatalandrogen exposureseemstobeinvolvedinthedevelopmentofsexualorientation in women largely based on findings that pertain to relative finger lengths (e.g., lesbianshavea lowerand thusmoremasculine 2D:4D finger length ratio than heterosexual women; Grimbos, Dawood,Burriss,Zucker,&Puts, 2010;Williamset al., 2000),but also based on evidence pertaining to the auditory system (i.e., lesbians haveweaker and thusmoremasculinized, otoacoustic emissions than heterosexual women; McFadden, 2011). For men, the existingresearch,especiallywhenconsidering2D:4Dratios(butalso otoacousticemissions), seemsto indicate thatadecrease inexposure toprenatalandrogens isnot related to thedevelopmentof sexualorientation.Thisconclusionstemsinpartfromanimalresearchdemonstrating how testosterone is related to sexual behavior in male animals (e.g., ‘‘Testosterone permits the behavior to be displayed, but does not explain variance in that behavior,’’Breedlove, 2017), and from the existing literature on 2D:4D ratios inmen,which has generally foundinconclusiveornull evidenceofanassociationbetween 2D:4D ratios and sexual orientation in men (Grimbos et al., 2010; Williams et al., 2000). We agree that there seems to bemore evidence of a straightforward association between prenatal hormones and sexual orientation inwomen.We also agree that there is evidence suggesting that amorenuancedor complexassociationbetweenprenatal hormones and sexual orientation exists inmen.However, there is also someevidence suggestingunder-androgenizationmight still occur ingaymen.Thus,wepropose thataprenatalhormoneassociation for the development of sexual orientation in men is complex, with some gay men experiencing hyper-androgenization, othergaymenexperiencingtypicallevelsofandrogensduringdevelopment, andstill othergaymenexperiencinghypo-or lowandrogenization. This complex association is shown in some studies in the research literature examining biomarkers other than 2D:4D (orones incombinationwith2D:4D) in relation to sexualorientation inmen. In thisCommentary,we focusonsuchwork that suggests that there is often a complex association between biomarkersofprenatalandrogensandsexualorientationinmen.Indeed, in somerecentwork,wefoundacomplexassociationbetweenfacial structure and sexual orientation in men, with some results suggesting that lowandrogenizationmight explain at least part of the association. Our study on the relationship between facial structure and sexual orientation(Skorska,Geniole,Vrysen,McCormick,&Bogaert,2015) showedthatgaymendifferedfromheterosexualmenon11facialfeatures at the univariate level and three on a unique,multivariate level. There was a mixture of facial features that differed in a sex atypical way, facial features that differed in a sex typical way, and facial features thatdifferedinwaysthatwereunrelatedtosex(seeTable3in Skorska et al., 2015). Using discriminant function analysis (which includeddatafrombothmenandwomen) to reduce thevariousfacial structure predictors based on their common associations, we further showed that there seemed to be two functions that summarized the data:onefunctionthatwasrelatedtosexualdifferentiationandonethat wasunrelatedtosexualdifferentiation(seeFig. 2 inSkorskaetal., 2015). To us, this suggests that prenatal hormones—including low androgenization—are still one plausible explanation for at leastsomeoftherelationshipbetweenfacialstructureandsexual orientation inmen, even if it cannot explain all the variation and even if we did not explicitly measure prenatal hormone levels. As afinal commentonSkorskaet al. (2015), however,wealso & Malvina N. Skorska mskorska@brocku.ca

Sexual Orientation: Biological Influences

This article is a revision of the previous edition by E. Stein, volume 21, pp. 13995–13998,