Sexual orientation and fluctuating asymmetry in men and women

Femme/Butch/Androgyne Identity and Preferences for Femininity Across Face, Voice, and Personality Traits in Chinese Lesbian and Bisexual Women

Studies indicate that individuals preferring masculinity/femininity in one domain also prefer it in other domains. Heterosexual men and women and gay men have reported consistent preferences for masculinity/femininity across the faces and voices of their preferred sex. This study explored the femininity preferences of 417 Chinese lesbian and bisexual women in terms of face, voice pitch, vocal tract length, and personality traits and explored the effect of sexual self-labels (femme, butch, and androgyne) on these preferences. We found that lesbian and bisexual women showed a stronger preference for feminized faces, voice pitch, vocal tract length, and personality traits than masculinized versions, and these preferences were highly consistent across the four domains. Moreover, femininity preference was moderated by sexual self-labels, with butches preferring more feminine voice pitch, vocal tract length, and personality traits than femmes and androgynes. However, no significant difference was found for facial femininity preferences among different sexual self-labels. These findings present evidence of consistent femininity preference across visual, auditory, and personality traits and suggest that, regardless of sexual orientation, multiple cues may be used together when determining the attractiveness of individuals. Furthermore, these results support the hypothesis that the partner preference of lesbian and bisexual women mirrors that of heterosexual men.

Individual differences in the biological basis of androphilia in mice and men

For nearly 60 years since the seminal paper from W.C Young and colleagues (Phoenix et al., 1959), the principles of sexual differentiation of the brain and behavior have maintained that female-typical sexual behaviors (e.g., lordosis) and sexual preferences (e.g., attraction to males) are the result of low androgen levels during development, whereas higher androgen levels promote male-typical sexual behaviors (e.g., mounting and thrusting) and preferences (e.g., attraction to females). However, recent reports suggest that the relationship between androgens and male-typical behaviors is not always linear - when androgen signaling is increased in male rodents, via exogenous androgen exposure or androgen receptor overexpression, males continue to exhibit male-typical sexual behaviors, but their sexual preferences are altered such that their interest in same-sex partners is increased. Analogous to this rodent literature, recent findings indicate that high level androgen exposure may contribute to the sexual orientation of a subset of gay men who prefer insertive anal sex and report more male-typical gender traits, whereas gay men who prefer receptive anal sex, and who on average report more gender nonconformity, present with biomarkers suggestive of low androgen exposure. Together, the evidence indicates that for both mice and men there is an inverted-U curvilinear relationship between androgens and sexual preferences, such that low and high androgen exposure increases androphilic sexual attraction, whereas relative mid-range androgen exposure leads to gynephilic attraction. Future directions for studying how individual differences in biological development mediate sexual behavior and sexual preferences in both mice and humans are discussed.

Aesthetic as genetic: The epistemological violence of gaydar research

In recent years, “gaydar” has come under increasing scientific scrutiny. Gaydar researchers have found that we can accurately judge sexual orientation at better than chance levels from various nonverbal cues. Why they could find what they did is typically chalked up to gender inverted phenotypic variations in craniofacial structure that distinguish homosexuals. This interpretation of gaydar data (the “hegemonic interpretation”) maintains a construction of homosexuality as both a “natural kind” and an “entitative” category. As a result, culturally and historically contingent markers of homosexuality are naturalized under the guise of gaydar. Of significant relevance to this article’s critique of gaydar research is that the hegemonic interpretation is presented as politically advantageous for LGB people by its authors, an undertheorized assumption that risks sanctioning an epistemological violence with unfortunate, demobilizing sociopolitical consequences. This critique is contextualized within current debates regarding intimate/sexual citizenship and advocates, instead, for a queer political ethic that considers such cultural erasure to be politically untenable.

Handedness is a biomarker of variation in anal sex role behavior and Recalled Childhood Gender Nonconformity among gay men

Developmental theories of the biological basis of sexual orientation suggest that sexually differentiated psychological and behavioural traits should be linked with sexual orientation. Subgroups of gay men delineated by anal sex roles differ according to at least one such trait: gender expression. The present study assessed the hypothesis that handedness, a biologically determined sexually differentiated trait, corresponds to differences in subgroups of gay men based on anal sex role. Furthermore, it assessed whether handedness mediates the association between gender nonconformity and male sexual orientation. Straight and gay men (N = 333) completed the Edinburgh Inventory of Handedness and the Recalled Childhood Gender Nonconformity Scale. Gay men also completed measures of anal sex role preference. As in previous studies, gay men showed greater non-right-handedness and gender nonconformity than straight men. Also, among gay men, bottoms/versatiles (i.e., gay men who take a receptive anal sex role, or who take on both a receptive and insertive anal sex role) were more gender-nonconforming than tops (i.e., gay men who take an insertive anal sex role). In support of the hypothesis, bottoms/versatiles were more non-right-handed than tops and handedness mediated the male sexual orientation and anal sex role differences in Recalled Childhood Gender Nonconformity. Together, these findings suggest that developmental processes linked to handedness underpin variation among men in sexual orientation and gender nonconformity as well as variation among subgroups of gay men that are delineated by anal sex roles.

The Relationship Between Digit Ratio (2D:4D) and Sexual Orientation in Men from China

We examined the relationship between 2D:4D digit ratio and sexual orientation in men from China and analyzed the influences of the components used to assess sexual orientation and the criteria used to classify individuals as homosexual on this relationship. A total of 309 male and 110 female participants took part in a web-based survey. Our results showed that heterosexual men had a significantly lower 2D:4D than heterosexual women and exclusively homosexual men had a significantly higher left 2D:4D than heterosexual men whereas only exclusively homosexual men had a significantly higher right 2D:4D than heterosexual men when sexual orientation was assessed via sexual attraction. The left 2D:4D showed a significant positive correlation with sexual identity, sexual attraction, and sexual behavior, and the right 2D:4D showed a significant positive correlation with sexual attraction. The effect sizes for differences in 2D:4D between homosexual and heterosexual men varied according to criteria used to classify individuals as homosexual and sexual orientation components; the more stringent the criteria (scores closer to the homosexual category), the larger the effect sizes; further, sexual attraction yielded the largest effect size. There were no significant effects of age and latitude on Chinese 2D:4D. This study contributes to the current understanding of the relationship between 2D:4D and male sexual orientation.

Fraternal Birth Order and Extreme Right-Handedness as Predictors of Sexual Orientation and Gender Nonconformity in Men

The present study explored whether there were relationships between number of older brothers, handedness, recalled childhood gender nonconformity (CGN), and sexual orientation in men. We used data from previous British studies conducted in our laboratory (N = 1,011 heterosexual men and 921 gay men). These men had completed measures of demographic variables, number and sex of siblings, CGN, and the Edinburgh Handedness Inventory. The results did not replicate the fraternal birth order effect. However, gay men had fewer "other siblings" than heterosexual men (even after controlling for the stopping-rule and family size). In a sub-sample (425 gay men and 478 heterosexual men) with data available on both sibling sex composition and handedness scores, gay men were found to show a significantly greater likelihood of extreme right-handedness and non-right-handedness compared to heterosexual men. There were no significant effects of sibling sex composition in this sub-sample. In a further sub-sample (N = 487) with data available on sibling sex composition, handedness, and CGN, we found that men with feminine scores on CGN were more extremely right-handed and had fewer other-siblings compared to masculine scoring men. Mediation analysis revealed that handedness was associated with sexual orientation directly and also indirectly through the mediating factor of CGN. We were unable to replicate the fraternal birth order effect in our archived dataset but there was evidence for a relationship among handedness, sexual orientation, and CGN. These data help narrow down the number of possible neurodevelopmental pathways leading to variations in male sexual orientation.

Prenatal Influences on Sexual Orientation: Digit Ratio (2D:4D) and Number of Older Siblings

Prenatal androgen levels are suggested to influence sexual orientation in both sexes. The 2D:4D digit ratio has been found to associate with sexual orientation, but published findings have often been contradictory, which may partly be due to the large ethnic diversity between and within studied populations. In men, number of older brothers has been found to correlate positively with homosexuality. This phenomenon has been explained with a maternal immune reaction, which is provoked only by male fetuses and which gets stronger after each pregnancy. Here we assessed the relationship of sexual orientation to 2D:4D ratios and number of older siblings in Finland, where the population is found to be genetically relatively homogeneous. As in many previous studies, heterosexual men had lower 2D:4D than non-heterosexual men, which supports the notion that non-heterosexual men experience higher androgen levels in utero than population norms. Contrary to previous reports, non-heterosexual women had higher 2D:4D than heterosexual women. Non-heterosexual men had more older brothers and older sisters than heterosexual men. The greater number of older sisters in non-heterosexual men indicates that there are other factors that contribute to the higher birth order of homosexual men than the maternal immunization.

The 2D:4D digit ratio is not a useful marker for prenatal famine exposure: Evidence from the Dutch hunger winter families study

OBJECTIVES

Digit lengths, and in particular the ratio of the 2nd (2D) to 4th (4D) digit (2D:4D), are stable in adulthood and have been linked to characteristics thought to have developmental origins, but little research has focused on early life determinants of these measures. We examined whether exposure to acute famine during specific periods of gestation was associated with 2D, 4D or the 2D:4D ratio.

METHODS

We studied men and women (1) born in one of three hospitals in western Netherlands whose mothers were exposed to a limited period of famine immediately prior to or during the pregnancy (n = 337); (2) born in the same hospitals to mothers not exposed to famine during the pregnancy (n = 271) or same-sex siblings of individuals in Groups 1 and 2 (n = 295). We measured 2D and 4D on both hands using calipers and computed the 2D:4D ratio.

RESULTS

Mean 2D and 4D lengths were 73.5 (SD 5.1) and 75.0 (5.4) mm, respectively. The 2D:4D ratio was 0.981 (SD 0.030). Both 2D and 4D were associated with male gender and height (all P < 0.001), and weakly with BMI. The 2D:4D ratio was 0.0070 (95% confidence interval 0.0017, 0.0123) lower among males as compared with females, and was not significantly associated with height (0.0002 per cm; 95% -0.0001, 0.0005). The 2D:4D ratio was not significantly associated with exposure to famine, overall (-0.0010, 95% CI 0.0030, 0.0050) or within any period of gestation.

CONCLUSIONS

The 2D:4D ratio is not significantly affected by prenatal exposure to famine and therefore is not a useful marker for generalized prenatal undernutrition.

Scientometric analysis and bibliography of digit ratio (2D:4D) research, 1998-2008

A scientometric analysis of modern research on the second-to-fourth digit ratio (2D:4D), a widely studied putative marker for prenatal androgen action, is presented. In early 2009, this literature totalled more than 300 publications and, since its initiation in 1998, has grown at a rate slightly faster than linear. Key findings included evidence of publication bias and citation bias, incomplete coverage and outdatedness of existing reviews, and a dearth of meta-analyses in this field. 2D:4D research clusters noticeably in terms of researchers, institutions, countries, and journals involved. Although 2D:4D is an anthropometric trait, most of the research has been conducted at psychology departments, not anthropology departments. However, 2D:4D research has not been predominantly published in core and specialized journals of psychology, but rather in more broadly scoped journals of the behavioral sciences, biomedical social sciences, and neurosciences. Total citation numbers of 2D:4D papers for the most part were not larger than their citation counts within 2D:4D research, indicating that until now, only a few 2D:4D studies have attained broader interest outside this specific field. Comparative citation analyses show that 2D:4D research presently is commensurate in size and importance to evolutionary psychological jealousy research, but has grown faster than the latter field. In contrast, it is much smaller and has spread more slowly than research about the Implicit Association Test Fifteen conjectures about anticipated trends in 2D:4D research are outlined, appendixed by a first-time bibliography of the entirety of the published 2D:4D literature.

A critical re-evaluation of the association between 2D:4D ratios and fluctuating asymmetry in humans

BACKGROUND

Both asymmetry and the second and fourth digit ratio (2D:4D) relate to various aspects of human life history. Higher asymmetry with extreme 2D:4D ratios have suggested a link between both processes, indicating that early development determines levels of developmental instability. However, most observed associations may be biased because combinations of the digit lengths are used as both dependent and independent variables.

AIM

The present study explored the usefulness of asymmetry in digits 2 and 4 to study this association.

SUBJECTS AND METHODS

A combination of literature review, a small simulation study, and a study of 2D:4D ratios and asymmetry in a total of 100 young males and females is presented.

RESULTS

Using asymmetry in digits 2 and 4 results in bias and increased type I error rates, leading to stronger associations between asymmetry and 2D:4D ratios. In spite of low sample sizes, significant associations between asymmetry measured in hands and face and 2D:4D ratios were detected for asymmetries in digits 2 and 4 only.

CONCLUSIONS

Using asymmetry in digits 2 and/or 4 causes bias. Excluding such results, there is currently little evidence of any association between asymmetry and digit ratios. Future studies should carefully select traits to investigate these correlations further.

Sexual orientation matters in sexual medicine

INTRODUCTION

Homosexuality is a topic that needs to be integrated into the knowledge base of the practitioner of sexual medicine.

AIM

To present to the reader a summary of the current literature on homosexuality and sexual orientation and address specifically issues that pertain to the relationship sexual orientation and sexual medicine practice.

MAIN OUTCOME MEASURES

The information is presented in a continued medical education format, with a series of evaluation questions at the end of the activity. Methods. A review of the literature is presented and organized according to the authors' judgment of the value of the information as to provide the reader with an inclusive panorama of the issues covered.

RESULTS

Current concepts, debates, and need for further research are presented.

CONCLUSIONS

The professional of sexual medicine needs to be aware of the various topics reviewed in this article as his or her involvement in the area of sexuality can create the expectation on the part of the patients of knowingness of all aspects of human sexuality. Sexual orientation is a complex area but considerable understanding has fortunately been achieved in many issues in reference to homosexuality and heterosexuality.

Fluctuating asymmetry and sexual orientation in men and women

The present study measured handedness and bodily fluctuating asymmetry (FA), two markers of developmental instability, in 89 heterosexual and 78 gay men and women. Asymmetry in ear breadth, ear length, ankle breadth, second digit length, fourth digit length, and two composite indices were calculated for each participant and a modified Edinburgh Inventory was used to assess handedness. Results showed that, for men, there was a significant positive correlation between three measures of FA and sexual orientation scores (SOS). As ear breadth FA and two composite FA scores increased so did SOS on a modified Kinsey scale (where 0 indicated exclusive heterosexuality and 6 indicated exclusive homosexuality). No significant relationships were found between SOS and FA for women. Similarly, sexual orientation was not related to handedness for either sex. The theoretical implications of the present results are discussed.