Sexual Orientation Affects Neural Responses to Subtle Social Aggression Signals.

The current series of studies are the first to examine brain responses to social aggression signals as a function of male and female sexual orientation. For the first set of studies (1a, 1b), axillary sweat had been collected from 17 heterosexual men and 17 heterosexual women aggressively responding to frustrating opponents (aggression condition) and while playing a construction game (control condition). Sweat samples were pooled according to sex and condition, and presented via a constant flow olfactometer to 17 gay and 23 heterosexual men (Study 1a), and 19 lesbian and 25 heterosexual women (Study 1b). Ongoing EEG was recorded from 61 scalp locations, chemosensory event-related potentials (CSERPs; P2, P3-1, P3-2) were analyzed, and neuronal sources calculated (low resolution electromagnetic tomography). Within the second set of studies (2a, 2b), pictures of males' and females' weak angry and neutral facial expressions were presented to 21 gay and 23 heterosexual men (Study 2a), and 19 lesbian and 26 heterosexual women (Study 2b), and ERPs (N170, P3) were analyzed. Gay men showed larger P3-1 amplitudes than heterosexual men upon presentation of male aggression sweat, accompanied by activation of the right inferior frontal gyrus (IFG, BA 10). Gay men also displayed longer N170 latencies in response to men's compared to women's angry facial expressions, while heterosexual men did not. In women, sexual orientation did not affect the processing of aggression sweat or anger expressions. Gay men showed preferential processing of chemosensory aggression signals (P3-1 amplitudes), indicating fine-tuned socioemotional sensitivity, related to activation of brain areas involved in emotion regulation (IFG). They further process the relative relevance of visual aggression signals (N170 latency). These results were in line with theories proposing a common evolutionary pathway for same-sex attraction and traits easing social integration.

Stability and Change in Sexual Orientation and Genital Arousal over Time.

Longitudinal work suggests that sexual orientation can change over time in men and women. These studies, however, may be susceptible to the bias of self-report. The current study therefore examined self-reported sexual orientation in addition to an objective correlate: genital arousal to erotic videos showing males or females. For 52 men (19 heterosexual, 19 bisexual, 14 homosexual) and 67 women (31 heterosexual, 18 bisexual, 18 homosexual), these measures were taken twice, with approximately 1 year between sessions. For self-reported sexual orientation, women reported lower relative stability (weaker correlation) than men over time, even though women did not change more overall (no stronger mean difference) than men between sessions. Bisexual individuals reported lower relative stability and more mean change than heterosexual and homosexual individuals. For genital arousal, across all groups, response patterns were correlated over time to a similar extent and showed little difference between sessions. Moreover, change in self-reported sexual orientation did not correspond with the change in genital arousal, regardless of sex. Perhaps self-reports overestimate changes in sexual orientation, since these changes were not reflected in physiological sexual response.

Cognitive processing of sexual cues in asexual individuals and heterosexual women with desire/arousal difficulties.

Asexuality is defined as a unique sexual orientation characterized by a lack of sexual attraction to others. This has been challenged, with some experts positing that it is better explained as a sexual dysfunction. Sexual Interest/Arousal Disorder (SIAD) is characterized by absent/reduced sexual interest/arousal paired with personal distress, with two subtypes: acquired and lifelong. Research suggests that while asexuality and acquired SIAD are distinct entities, there may be overlap between asexuality and lifelong SIAD. Findings from studies using eye-tracking and implicit association tasks suggest that these methodologies might differentiate these groups on the basis of their neural mechanisms. However, no study has compared their cognitive processing of sexual cues, and the literature on lifelong SIAD is minimal. The current study tested differences in the cognitive processing of sexual cues between asexual individuals and women with SIAD (lifelong and acquired). Forty-two asexual individuals and 25 heterosexual women with SIAD (16: acquired; 9: lifelong) completed three study components: a visual attention task, a Single Category-Implicit Association Task, and the sex semantic differential. ANOVAs examined group differences in: 1) visual attention to erotic cues, 2) implicit appraisals of sexual words, and 3) explicit appraisals of sex. Women with SIAD displayed a controlled attention preference for erotic images and areas of sexual contact, with longer dwell times to these areas relative to asexual individuals, who did not gaze preferentially at erotic cues. For implicit appraisals, all groups demonstrated negative-neutral implicit associations with sexual words. For explicit appraisals, women with acquired SIAD reported more positive evaluations of sex relative to asexual individuals and women with lifelong SIAD. This project sheds light on key differences between asexuality and low desire, and has implications for best clinical practice guidelines for the assessment of lifelong SIAD.

Brain structure changes associated with sexual orientation.

Biological sex differences in brain function and structure are reliably associated with several cortico-subcortical brain regions. While sexual orientation (hetero- versus homosexuality) has been similarly linked to functional differences in several phylogenetically-old brain areas, the research on morphological brain phenotypes associated with sexual orientation is far from conclusive. We examined potential cerebral structural differences linked to sexual orientation in a group of 74 participants, including 37 men (21 homosexual) and 37 women (19 homosexual) using voxel-based morphometry (VBM). Gray matter volumes (GMV) were compared with respect to sexual orientation and biological sex across the entire sample using full factorial designs controlling for total intracranial volume, age, handedness, and education. We observed a significant effect of sexual orientation for the thalamus and precentral gyrus, with more GMV in heterosexual versus homosexual individuals, and for the putamen, with more GMV in homosexual + than heterosexual individuals. We found significant interactions between biological sex and sexual orientation, indicating that the significant effect for the putamen cluster was driven by homosexual women, whereas heterosexual women had increased precentral gyrus GMV. Heterosexual men exhibited more GMV in the thalamus than homosexual men. This study shows that sexual orientation is reflected in brain structure characteristics and that these differ between the sexes. The results emphasize the need to include or control for potential effects of participants' sexual orientation in neuroimaging studies. Furthermore, our findings provide important new insights into the brain morphology underlying sexual orientation and likely have important implications for understanding brain functions and behavior.

Heterosexual, gay, and lesbian people's reactivity to virtual caresses on their embodied avatars' taboo zones.

Embodying an artificial agent through immersive virtual reality (IVR) may lead to feeling vicariously somatosensory stimuli on one's body which are in fact never delivered. To explore whether vicarious touch in IVR reflects the basic individual and social features of real-life interpersonal interactions we tested heterosexual men/women and gay men/lesbian women reacting subjectively and physiologically to the observation of a gender-matched virtual body being touched on intimate taboo zones (like genitalia) by male and female avatars. All participants rated as most erogenous caresses on their embodied avatar taboo zones. Crucially, heterosexual men/women and gay men/lesbian women rated as most erogenous taboo touches delivered by their opposite and same gender avatar, respectively. Skin conductance was maximal when taboo touches were delivered by female avatars. Our study shows that IVR may trigger realistic experiences and ultimately allow the direct exploration of sensitive societal and individual issues that can otherwise be explored only through imagination.

Handedness and Birth Order Among Heterosexual Men, Gay Men, and Sao Praphet Song in Northern Thailand.

Previous research has examined handedness and birth order to inform sexual orientation and gender identity/role expression development; however, sexual orientation and gender identity/role expression have rarely been disentangled to provide a more nuanced perspective. In Thailand, we investigated sexual orientation and gender identity simultaneously via comparison of 282 heterosexual men, 201 gay men, and 178 sao praphet song-i.e., androphilic, markedly feminine males recognized as a "third" gender. Handedness was examined as: extremely left-handed, moderately left-handed, ambidextrous, moderately right-handed, or extremely right-handed. Birth order was examined as numbers of older and younger brothers and sisters, by using Berglin's, fraternal, and sororal indices, and by examining the older brother odds ratio and sibling sex ratio. Compared with heterosexual men, gay men and sao praphet song were more likely to be extremely right-handed. Sao praphet song were also more likely to be extremely left-handed than heterosexual and gay men. Heterosexual men and sao praphet song had later sororal birth order compared with the expected Thai population value, suggesting stopping rules influenced when probands' mothers ceased having children. These findings provide new insights and replicate previous findings in a non-Western sample. Regarding handedness, in males, mechanisms related to extreme right-handedness likely influence the development of androphilia, whereas mechanisms related to both extreme right- and extreme left-handedness likely explain the combination of androphilia and feminine gender identity/role expression. Regarding birth order, similar to the conclusions of some prior research, stopping rules pose a challenge for testing the fraternal birth order effect.

Understanding heterosexual women's erotic flexibility: the role of attention in sexual evaluations and neural responses to sexual stimuli.

Many women experience desires, arousal and behavior that run counter to their sexual orientation (orientation inconsistent, 'OI'). Are such OI sexual experiences cognitively and neurobiologically distinct from those that are consistent with one's sexual orientation (orientation consistent, 'OC')? To address this question, we employed a mindful attention intervention-aimed at reducing judgment and enhancing somatosensory attention-to examine the underlying attentional and neurobiological processes of OC and OI sexual stimuli among predominantly heterosexual women. Women exhibited greater neural activity in response to OC, compared to OI, sexual stimuli in regions associated with implicit visual processing, volitional appraisal and attention. In contrast, women exhibited greater neural activity to OI, relative to OC, sexual stimuli in regions associated with complex visual processing and attentional shifting. Mindfully attending to OC sexual stimuli reduced distraction, amplified women's evaluations of OC stimuli as sexually arousing and deactivated the superior cerebellum. In contrast, mindfully attending to OI sexual stimuli amplified distraction, decreased women's evaluations of OI stimuli as sexually arousing and augmented parietal and temporo-occipital activity. Results of the current study constrain hypotheses of female erotic flexibility, suggesting that sexual orientation may be maintained by differences in attentional processing that cannot be voluntarily altered.

Behavioral intention to have risky sex in young men and women: The role of sexual excitation and assertiveness.

Due to the complex role of sexual excitation in risky sexual behaviors, this study aimed to disentangle this phenomenon by jointly analyzing the combined role of three forms of sexual excitation: genital and subjective, and individual´s propensity. Therefore, we examined the relationship between the components of the Dual Control Model, that is, propensity for sexual excitation/inhibition, in addition to genital and subjective arousal, and sexual assertiveness and intention to engage in casual sexual encounters in which sexual risk was implicitly or explicitly present. The sample consisted of 99 heterosexual young adults (55 men and 45 women) with ages ranging from 18 to 32 years. Participants performed an experiment in the laboratory, which involved them watching a sexual clip and then being presented with two erotic excerpts (stories) depicting casual sexual encounters in which there was an existence of implicit and explicit sexual risks. In men, the propensity for sexual inhibition was the most determining variable in preventing them from sexual risk-taking. In women, intention to engage in risky sexual behaviors was better determined by their propensity for sexual excitation and sexual assertiveness in negotiating the use of contraceptive methods. This research highlights the relevance of excitation and inhibition as a trait, in addition to subjective arousal and sexual assertiveness in intention to engage in risky sexual behaviors.

Sexual Arousal Patterns of Mostly Heterosexual Men.

Mostly heterosexual men describe themselves as slightly bisexual, with predominant sexual attraction to women but occasional attraction to men. After "completely heterosexual," "mostly heterosexual" is the most common male sexual orientation, by self-report. However, self-reported bisexual feelings among men can diverge from patterns of genital arousal, an objective measure of sexual interest with high validity. We compared 49 mostly heterosexual and 50 completely heterosexual men's patterns of genital and subjective sexual arousal to male and female erotic stimuli. In addition, we compared these groups on relevant self-report measures pertaining to sexual feelings, identity, and behavior. Results supported increased bisexual arousal with respect to self-report and genital arousal pattern among the mostly heterosexual men, compared with the completely heterosexual men. Furthermore, mostly heterosexual men reported more childhood gender nonconformity, greater male sex partners, and less self-reported disgust or aversion to sex acts with men. "Mostly heterosexual" appears to be a gradation of male sexual orientation associated with unique genital arousal patterns, among other correlates.

Through a glass, darkly: Human digit ratios reflect prenatal androgens, imperfectly.

On average, the length of the index finger (digit 2) divided by the length of the ring finger (digit 4) on the right hand, is greater in women than in men. Converging evidence makes it clear that prenatal androgens affect the development of digit ratios in humans and so are likely responsible for this sex difference. Thus, differences in 2D:4D between groups within a sex may be due to average differences between those groups in prenatal androgen exposure. There have been many reports that lesbians, on average, have a smaller (more masculine) digit ratio than straight women, which has been confirmed by metaanalysis. These findings indicate that lesbians were, on average, exposed to greater prenatal androgen than straight women, which further indicates that greater levels of prenatal androgen predispose humans to be attracted to women in adulthood. Nevertheless, these results only apply to group differences between straight women and lesbians; digit ratios cannot be used to classify individual women as gay or straight.

Using Sexual Selection Theories to Examine Contextual Variation in Heterosexual Women's Orientation Toward High Heels.

High heels are symbols of female sexuality and are "costly signals" if the risks of wearing them are offset by improving women's attractiveness to men. From a functionalist perspective, the costs versus benefits of wearing heels may vary according to personal and contextual factors, such as her effectiveness at competing for mates, or at times when such motives are stronger. Here, we examined potential differences between women (self-rated attractiveness, dyadic versus solitary sexual desire, women's age, competitive attitudes toward other women) and contextual variation (priming mating and competitive motives) in their responses to high heels. Study 1 (N = 79) and Study 2 (N = 273) revealed that self-rated attractiveness was positively related to orientation toward heeled shoes. When examining responses to two very attractive shoes (one higher heel, one lower heel) in Study 2, dyadic sexual desire, but not solitary sexual desire or intrasexual competitiveness, predicted their inclination to buy the higher-heeled shoe. In Study 3 (N = 142), young women chose high heels when primed with free choice of a designer shoe (95% CI [53.02 mm, 67.37 mm]) and preferred a heel 22 mm (0.87") higher than older women (Study 4, N = 247). Contrary to predictions, priming mating or competitive motives did not alter women's preference toward a higher heel (Studies 3 and 4). Our studies suggest that attractive women augment their physical appeal via heels. High heels may be a subtle indicator of dyadic sexual desire, and preferences for heels are stronger at times in the lifespan when mating competition is relatively intense.

Neural Responses to Sexual Stimuli in Heterosexual and Homosexual Men and Women: Men's Responses Are More Specific.

Patterns of genital arousal in response to gendered sexual stimuli (i.e., sexual stimuli presenting members of only one sex at a time) are more predictive of men's than of women's sexual orientations. Additional lines of evidence may shed light on the nature of these differences. We measured neural activation in homosexual and heterosexual men and women using fMRI while they viewed three kinds of gendered sexual stimuli: pictures of nude individuals, pictures of same-sex couples interacting, and videos of individuals self-stimulating. The primary neural region of interest was the ventral striatum (VS), an area of central importance for reward processing. For all three kinds of stimuli and for both VS activation and self-report, men's responses were more closely related to their sexual orientations compared with women's. Furthermore, men showed a much greater tendency to respond more positively to stimuli featuring one sex than to stimuli featuring the other sex, leading to higher correlations among men's responses as well as higher correlations between men's responses and their sexual orientations. Whole-brain analyses identified several other regions showing a similar pattern to the VS, and none showed an opposite pattern. Because fMRI is measured identically in men and women, our results provide the most direct evidence to date that men's sexual arousal patterns are more gender specific than women's.

An Exploratory Study on the Central Nervous Correlates of Sexual Excitation and Sexual Inhibition.

The Sexual Inhibition/Sexual Excitation Scales (SIS/SES) measure sexual excitation and sexual inhibition proneness. We used SIS and SES scores of 62 heterosexual teleiophilic men (Mage 34.3, SD = 9.9) to predict brain activation levels during the presentation of male and female visual sexual stimuli in a magnetic resonance imaging (MRI) scanner. Statistical analyses revealed significant correlations. SES and SIS1 scores were positively associated with brain activation in various brain regions during the presentation of both male and female stimuli. SIS2 turned out to be a weaker predictor of brain activation, still revealing one significant correlation in the right lateral orbitofrontal cortex. Significant regions for SES and SIS1 were, among others, primary and supplementary motor areas, the caudate nucleus, the dorsal anterior cingulate cortex, anterior insula, and prefrontal areas. Our study can be seen as an exploratory investigation of SIS and SES with means of functional brain imaging. The results provide a promising contribution to the assertion of neurophysiological systems of sexual inhibition and excitation proneness.

Mu-Suppression as an Indicator of Empathic Processes in Lesbian, Gay, and Heterosexual Adults.

Self-reported empathy differs with gender and sexual orientation. The current study investigated whether mu-suppression, reflecting brain activity especially related to state empathy, also is modulated by gender and sexual orientation. Pictures of painful and non-painful actions were presented to 20 lesbians, 20 gay men, 20 heterosexual men and 20 heterosexual women, while EEG was recorded. Individual peak frequencies of mu-activity (electrodes C3, C4) were detected within the 6-11 Hz band for each participant, and mu-suppression indices were calculated. Further, verbal indicators of state empathy (pain ratings) and compassion were assessed. Only heterosexual individuals showed the typical pattern of enhanced mu-suppression in response to painful relative to non-painful pictures. Lesbian women and gay men did not show a differential mu-response. Moreover, they felt less compassion compared to heterosexual individuals. In line with this finding, the more compassion the participants reported, the stronger the mu-suppression in response to painful relative to non-painful pictures was. Pain ratings did not vary with sexual orientation. The lesser compassion reported by lesbian women and gay men is discussed as a mediator of their non-differential mu-suppression response. It is hypothesized that this pattern might relate to gay men and lesbian women tending to perceive the anonymous depicted actors as outgroup members, hence showing less compassion and reduced mu-suppression. As empathy is often related to negative feelings (empathic stress), a clear distinction between individuals to empathize with versus individuals not to emphasize with may well be an adaptive feature in same-sex oriented individuals.

Incidence of surrogacy in the USA and Israel and implications on women's health: a quantitative comparison.

PURPOSE: Gestational surrogacy (GS) has been researched in multiple qualitative studies. In contrast, quantitative aspects of the practice are conspicuously understudied. The present article assesses and compares the incidence of GS in the USA and Israel, two industrialized countries that have maintained active commercial surrogacy practice, for over two decades. METHOD: The article is a secondary analysis of GS figures published by the Israeli Parliament's Centre for Research and Information (2018) and by the USA's Centers for Disease Control (2016) and related professional publications. Each dataset is analyzed in reference to the respective country, so as to devise local incidence scores that are then juxtaposed in inter-country comparison. RESULTS: The incidence of GS rises steeply in both countries. Though US surrogates are contracted by local and international, heterosexual and gay, and partnered and single intended parents, the relative incidence of GS is lower in the USA than in Israel, where only local heterosexual couples could contract a gestational surrogate. An exceptionally high rate of multiple births was observed in both settings, suggesting some overlooking of professional recommendations for elective single-embryo transfer. CONCLUSION: GS incidence appears to resemble the ratio between the countries' respective fertility rates. The paper underscores two main risks facing gestational surrogates: the risk of not conceiving and not being paid and the risk of carrying a multiple pregnancy, which is extremely prevalent in GS pregnancies, and sustaining the short- and long-term health complications that are more prevalent in such pregnancies.

Father support is protective against the negative effects of perceived discrimination on CRP among sexual minorities but not heterosexuals.

BACKGROUND: Exposure to sexual orientation-related discrimination among sexual minorities may lead to elevated levels of C-reactive protein (CRP) as compared to their heterosexual counterparts. However, little is known about factors that may buffer the association between discrimination and CRP among sexual minorities versus heterosexuals. The current study examined if the association between discrimination, sexual orientation, and CRP differed across levels of social support from one's father/father-figure or mother/mother-figure between sexual minorities and heterosexuals. METHODS: Data came from Wave IV of the National Longitudinal Study of Adolescent to Adult Health (Add Health). The sample sizes for father support and mother support was 3167 and 3575, respectively. Participants ranged in age from 24 to 33 years. Stratified linear regression models examined if father and mother support moderated the association between discrimination and CRP among sexual minorities and heterosexuals. RESULTS: Father support significantly moderated the association between discrimination and CRP among sexual minorities but not heterosexuals. Sexual minorities with higher father support and who experienced discrimination had lower CRP as compared to those with lower father support and who experienced discrimination. Mother support did not moderate the association between discrimination and CRP among either sexual minorities or heterosexuals. CONCLUSION: Father support may mitigate the negative effects of stress from discrimination on CRP among sexual minorities. Future research should further examine the potential differential role that father support may play in reducing cardiovascular risk among sexual minorities versus heterosexuals who experience discrimination.

Relationship Context Moderates Couple Congruence in Ratings of Sexual Arousal and Pain During Vaginal Sensations in the Laboratory.

Genital pain is a social experience that needs to be studied as a dyadic interaction between partners. The present study relied on a sample of 42 heterosexual couples to examine the level of congruence between both partners' ratings of pain and sexual arousal in response to experimentally induced vaginal pressure that served as a simulation of vaginal sensations during penetration. We also inferred the men's ability to estimate their partner's level of pain and sexual arousal. Because the relationship has shown to influence pain estimations, we considered the moderating role of perceived partner responsiveness and relationship satisfaction. We found higher disagreement in pain ratings when vaginal pressure was induced in the context of a sexual film compared to a neutral film, with men overestimating the level of pain in women. Also sexual arousal ratings diverged between partners, with men underestimating their partners' level of sexual arousal during the induction of vaginal pressure, regardless of whether they were watching a sexual or neutral film. Importantly, the level of congruence between actual and estimated ratings of pain and sexual arousal depended on how relationally satisfied men and women were and how validated and supported women felt by their male partner. These results make an important contribution to the growing literature on the social determinants of sexual pain experiences.

What drives female objectification? An investigation of appearance-based interpersonal perceptions and the objectification of women.

Previous research finds that both men and women perceive sexualized women as lacking in certain human qualities such as mental capacity and moral status. The mechanism underlying this effect, however, is unclear. The present two studies test how appearance-based judgements affect the degree to which a broad sample of women are objectified. In Study 1 (N = 279), full-body images of women wearing different clothing outfits were rated by male and female participants on perceived attractiveness, sexual intent and age. In Study 2, male and female participants (N = 1,695) viewed these same images from Study 1 and rated them on two dimensions of objectification (agency and patiency). We analyzed associations between these dimensions of objectification and the averaged appearance-based perceptions from Study 1. We find that women perceived as more open to casual sex are attributed less mental capacity and less moral status. We also find that participants tend to associate attractiveness with greater mental and moral status in women, but we find only limited evidence that perceived age influences objectification. Our findings suggest that although positive attractiveness biases may mitigate the amount a woman is objectified, greater female objectification may be prompted by observers' negative stereotypes of promiscuous women.

Beliefs About Gender Predict Faking Orgasm in Heterosexual Women.

The majority of women have faked an orgasm at least once in their lives. In the current study, we assessed how women's worldviews about gender relate to their faking orgasm behavior. A survey of 462 heterosexual women from the UK (Mage=38.38 years) found that those who espoused anti-feminist values-that is, those high in hostile sexism-had faked significantly more orgasms over their lifetime. In contrast, those who espoused ostensibly positive but restrictive ideas of gender relations-that is, those high in benevolent sexism-had faked significantly fewer orgasms over their lifetime. Furthermore, the more that women believed female orgasm was necessary for men's sexual gratification, the more likely they were to have faked an orgasm at least once in their lives compared to women who had never faked an orgasm. These effects were small to moderate and emerged after controlling for demographics, sexual history, ease of orgasm, and previously established psychological correlates of faking orgasm, including suspected partner infidelity and intrasexual competition.

Human Papillomavirus Viral Load and Transmission in Young, Recently Formed Heterosexual Couples.

BACKGROUND: We studied the association between human papillomavirus (HPV) viral load (VL) and HPV concordance. METHODS: The HITCH cohort study included young, heterosexual, recently formed, sexually active couples. Questionnaires and genital samples were collected at 0 and 4 months. Samples were tested for HPV DNA by polymerase chain reaction (PCR; Linear Array). VLs of HPV6/11/16/18/31/42/51 were quantified using type-specific real-time PCR. Correlations between VL and type-specific HPV prevalence and incidence were evaluated using multilevel, mixed-effects linear/logistic regression models. RESULTS: We included 492 couples. VLs were higher in penile than vaginal samples. VL at subsequent visits correlated significantly within men (r, 0.373), within women (r, 0.193), and within couples (r range: 0.303-0.328). Men with high VL had more type-specific persistent HPV infections (odds ratio [OR], 4.6 [95% confidence interval {CI}, 2.0-10.5]). High VL in men was associated with prevalent (OR, 5.3 [95% CI, 2.5-11.2]) and incident (OR, 6.7 [95% CI, 1.5-30.7]) type-specific HPV infections in their partner. Women's VL was associated with type-specific HPV prevalence in their partner at the same (OR, 5.9) and subsequent (OR, 4.7) visit. CONCLUSIONS: Persistent HPV infections have limited VL fluctuations. VL between sex partners are correlated and seem predictive of transmission episodes.