Sexual Orientation Differences in Cerebral Asymmetry and in the Performance of Sexually Dimorphic Cognitive and Motor Tasks

With each of the tasks in the present studies we expected to find the reported sex difference between heterosexual women and heterosexual men and we predicted a sexual orientation effect with the performance of homosexual men being similar to that of heterosexual women and different from that of heterosexual men. Study I aimed to replicate earlier findings by recording the performance of a group of homosexual men on a visuospatial task, the Vincent Mechanical Diagrams Test (VMDT), a dot detection divided visual field measure of functional cerebral asymmetry, and on five subtests of the Wechsler Adult Intelligence Scale (WAIS). For each task the profile of scores obtained for the homosexual men was similar to that of heterosexual women in that they scored lower than heterosexual men on the VMDT, they showed less asymmetry, and they recorded a higher Verbal than Performance IQ on the WAIS. In Study 2, a male-biased targeted throwing task favored heterosexual men while, in contrast, on the female-biased Purdue Pegboard single peg condition heterosexual men were outperformed by heterosexual women and homosexual men. On neither of these two tasks did the performances of homosexual men and heterosexual women differ. One task, manual speed, yielded neither sex nor sexual orientation differences. Another, the Purdue Pegboard assemblies condition, revealed a sex difference but no sexual orientation difference. Failure to obtain a sexual orientation difference in the presence of a sex difference suggests that the sexual orientation effect may be restricted to a subset of sexually dimorphic tasks.     

The Cognitive, Behavioral, and Personality Profiles of a Male Monozygotic Triplet Set Discordant for Sexual Orientation

The neurohormonal theory of sexual orientation proposes that homosexual men and homosexual women are exposed prenatally to a hormonal environment that is similar to that of the other sex. Prenatal exposure to an opposite-sex hormonal environment may lead the nervous system to develop in a manner consistent with the opposite sex. If this cross-sex exposure occurs, one prediction would be that the cognitive ability profile of homosexual men would be similar to that of heterosexual women. This study examined a set of male monozygotic triplets, aged 21 years, discordant for sexual orientation: 2 of the triplets were heterosexual, 1 was homosexual. The triplets were administered measures of 23 domains of cognitive ability, as well as measures of sexual orientation and masculinity/femininity. On the measures of cognitive ability, the triplets performed similarly, yet consistent differences were found between the 2 heterosexual triplets and the 1 homosexual cotriplet. Differences having the same pattern were found for the number of Schafer homosexuality signs on the Rorschach, and on a homosexuality scale derived from items on the Minnesota Multiphasic Personality Inventory--2 (MMPI-2). Responses from the homosexual triplet were in a more feminine direction than responses from his 2 heterosexual cotriplets on measures of masculinity-femininity, which included measures derived from Rorschach responses, the MMPI-2 Masculinity-Femininity scale, the Bem Sex Role Inventory, and the Boyhood Gender Conformity Scale. Responses to the 16 Personality Factor Questionnaire also distinguished the 1 homosexual triplet from the 2 heterosexual cotriplets. These findings support the view that the prenatal hormonal environment may have enduring effects on selected behavioral traits.     

Sexual Partner Age Preferences of Homosexual and Heterosexual Men and Women

The sexual age preferences of 192 adults (equal groups of heterosexual men, heterosexual women, homosexual men, and homosexual women) were examined. Participants rated the sexual attractiveness of pictures of 15 male and 15 female faces arranged into five apparent average age categories ranging from 18 to 60 years. It was predicted that homosexual and heterosexual men would prefer younger partners of their preferred sex than would homosexual and heterosexual women and that age preference would not vary with participant age. Both predictions were supported, although homosexual women preferred older partners than expected. Results suggest that age and sex preferences develop independently.     

Sexual and Affective Responses to Same- and Opposite-Sex Stimuli in Heterosexual and Homosexual Men: Assessment and Manipulation of Visual Attention

Affective and cognitive factors play an important role in the activation and regulation of men’s sexual arousal. Barlow (1986) argued that initial affective reactions determine the allocation of attention to sexual stimuli. We applied Barlow’s model to our understanding of the role of sexual arousal in sexual orientation, where sexual arousal patterns have consistently been found to be congruent with self-reported orientation in men, but not in women. Visual attention of 28 heterosexual and 22 homosexual men to same- and opposite-sex erotic stimuli was assessed and experimentally-directed by means of a newly developed software application, while genital (penile rigidity) and affective responses (self-reported and physiological) were measured. In line with previous research, we found “category specificity” in men’s sexual arousal, in that sexual responses were strongest to orientation-congruent stimuli. Also, both homosexual and heterosexual men experienced stronger sexual responses to conditions in which their attention was directed to sexual versus nonsexual content of orientation-congruent stimuli. Only homosexual men manifested higher sexual responses when their visual attention was directed towards the sexual content of orientation-incongruent stimuli. Heterosexual men experienced weaker positive and stronger negative affective responses to orientation-incongruent content, suggestive of potential avoidance or inhibitory mechanisms.     

The Subtlety of Sex-Atypicality

Memories of sex-atypical behavior and interests in childhood usually differ between homosexual and heterosexual people. However, variation within these broad groups has not previously been explored in detail, especially among women. We utilized data from a postal survey of a nationwide sample of Australian adult twins (n = 4,901, age range: 19–52 years). Among men, 15.2% reported homosexual behavior (ever), 11.5% said they had been sexually attracted to the same sex, and 6.4% said they were not heterosexual; the corresponding figures for women were 7.9, 10.6, and 3.5%. A continuous measure of childhood gender nonconformity (CGN) was sensitive to slight variations in homosexual attraction and behavior. In particular, among both men and women who identified as heterosexual, there were significant differences between complete heterosexuals and those who admitted to only one or a few same-sex behaviors but no homosexual attraction. Among men, CGN scores distinguished between heterosexuals who admitted to same-sex behavior only and those who admitted to some homosexual attraction. The sexual subgroups also differed on a measure of gender atypicality in adulthood. Implications for developmental theories of sexuality are discussed.     

Patterns of Sexual Arousal in Homosexual,Bisexual, and Heterosexual Men

The purpose of this study was to determine if self-identified bisexual, heterosexual, and homosexual men show differential genital and subjective arousal patterns to video presentations of bisexual, heterosexual, male homosexual, and lesbian sexual interactions. It was predicted that, relative to heterosexual and homosexual stimuli, bisexual men would show the highest levels of sexual arousal to bisexual erotic material, while this stimulus would induce relatively low levels of response in heterosexual and homosexual men. A sample of 59 men (19 homosexual, 13 bisexual, and 27 heterosexual) were presented with a series of 4-min sexual videos while their genital and subjective sexual responses were measured continuously. Bisexual men did not differ significantly in their responses to male homosexual stimuli (depicting men engaging in sex) from homosexual men, and they did not differ significantly in their responses to heterosexual (depicting two women, without same-sex contact, engaged in sex with a man) and lesbian (depicting women engaging in sex) stimuli from heterosexual men. However, bisexual men displayed significantly higher levels of both genital and subjective sexual arousal to a bisexual stimulus (depicting a man engaged in sex with both a man and a woman) than either homosexual or heterosexual men. The findings of this study indicate that bisexuality in men is associated with a unique and specific pattern of sexual arousal.     

Sexual orientation and performance on sexually dimorphic motor tasks

Performance of homosexual and heterosexual men and women on two motor tasks which reliably demonstrate sex differences in opposite directions was examined. A Throw-to-Target Task and the Purdue Pegboard were administered to undergraduate students matched for age and program of study. A two-way ANOVA (Sex × Sexual Orientation) of the Throw data showed a significant interaction,F(1, 90) = 16.22,p 0.001, and a trend for an effect of sex,F(1, 90) = 3.72,p < 0.06. Heterosexual men outperformed heterosexual women, whereas gay men threw less accurately and lesbians tended to throw more accurately than their heterosexual counterparts. Differences in sports history or hand strength did not account for these effects. Analysis of the Pegboard scores found no interaction or main effect of sexual orientation, but the effect of sex was significant,F(1,63) = 7.01,p 0.02. Regardless of sexual orientation, women outperformed men and this difference remained significant even when a measure of finger size was partialed out. This study provides new evidence suggesting an association between sexual orientation and motor-performance profiles. As with cognitive tasks, the motor-performance profiles of homosexuals are composites of some male-typical and some female-typical abilities. To the extent that sociological factors have been controlled, the study suggests that both sexual orientation and motor/cognitive predispositions may have early biological contributions.This research was supported by a grant from the Medical Research Council, Ottawa, to D. Kimura.     

Recalled Separation Anxiety and Gender Atypicality in Childhood: A Study of Canadian Heterosexual and Homosexual Men and Women

The current study tested the hypothesis that elevated childhood separation anxiety is associated with female-typical childhood behavior and identity by comparing retrospective reports of heterosexual and homosexual men and women (N = 399). Participants completed measures of recalled childhood separation anxiety and childhood gender-atypical behavior and identity. Heterosexual men reported significantly less childhood separation anxiety relative to all other groups. Childhood gender atypicality was significantly positively correlated with childhood separation anxiety among homosexual men, but not among members of other participant groups. Discussion focused on the implications of these findings for the proposed hypothesis as well as future directions for research examining the bases of developmental associations among sex, sexual orientation, gender atypicality, and childhood separation anxiety.     

Detection of Sexual Orientation (“Gaydar”) by Homosexual and Heterosexual Women

Although there has been considerable research investigating the ability to identify sexual orientation from static images, or “gaydar,” few studies have considered the role of female sexual orientation or sexual interest (for example, sociosexual orientation) in judgment accuracy. In two studies, we investigated the sexuality detection ability, and masculinity and femininity as cues used in judgment. In Study 1, we recruited heterosexual (N = 55) and homosexual (N = 71) women to rate the sexual orientation of homosexual and heterosexual male and female targets (N = 80: 20 heterosexual men, 20 homosexual men, 20 heterosexual women, and 20 homosexual women). We found that detection accuracy was better than chance levels for both male and female targets and that male targets were more likely to be falsely labeled as homosexual than female targets were. Overall, female faces were more accurately identified as heterosexual or homosexual than male faces and homosexual female raters were biased towards labeling targets as homosexual. Sociosexuality did not influence the accuracy with which targets were identified as heterosexual or homosexual. In Study 2, 100 heterosexual and 20 homosexual women rated the stimulus for masculinity and femininity. Heterosexual women were rated as more feminine and less masculine than homosexual women and homosexual men were rated as more feminine and less masculine than heterosexual men. Sexual orientation of the judges did not affect the ratings. The results were discussed with a reference to evolutionary and cultural influences affecting sexual orientation judgment accuracy.     

Sex-Specificity in the Reward Value of Facial Attractiveness

Studies of the sex-specificity of sexual arousal in adults (i.e., the tendency to respond more strongly to preferred-sex individuals than non-preferred sex individuals) have suggested that heterosexual men, homosexual men, and homosexual women show stronger sex-specific responses than do heterosexual women. Evidence for a similar pattern of results in studies investigating the reward value of faces is equivocal. Consequently, we investigated the effects of (1) sexual orientation (homosexual vs. heterosexual), (2) sex (male vs. female), (3) image sex (preferred-sex vs. non-preferred-sex), and (4) the physical attractiveness of the individual shown in the image on the reward value of faces. Participants were 130 heterosexual men, 130 homosexual men, 130 heterosexual women, and 130 homosexual women. The reward value of faces was assessed using a standard key-press task. Multilevel modeling of responses indicated that images of preferred-sex individuals were more rewarding than images of non-preferred-sex individuals and that this preferred-sex bias was particularly pronounced when more physically attractive faces were presented. These effects were not qualified by interactions involving either the sexual orientation or the sex of our participants, however, suggesting that the preferred-sex bias in the reward value of faces is similar in heterosexual men, homosexual men, heterosexual women, and homosexual women.     

Self-Reported Sexual Desire in Homosexual Men and Women Predicts Preferences for Sexually Dimorphic Facial Cues

Recent studies investigating the relationship between self-reported sexual desire and attraction to same- and opposite-sex individuals have found that homosexual men’s sexual desire is positively correlated with their self-reported attraction to own-sex individuals only, while homosexual women’s sexual desire is positively correlated with their self-reported attraction to both men and women. These data have been interpreted as evidence that sexual desire strengthens men’s pre-existing (i.e., dominant) sexual behaviors and strengthens women’s sexual behaviors in general. Here we show that homosexual men’s (n = 106) scores on the Sexual Desire Inventory-2 (SDI-2) were positively correlated with their preferences for exaggerated sex-typical shape cues in own-sex, but not opposite-sex, faces. Contrary to the hypothesis that sexual desire strengthens women’s preferences for sexual dimorphism generally, homosexual women’s (n = 83) SDI-2 scores were positively correlated with their preferences for exaggerated sex-typical shape cues in opposite-sex faces only. Together with previous research in heterosexual subjects, our findings support the proposal that sexual desire increases the incidence of existing sexual behaviors in homosexual and heterosexual men, and increases the incidence of sexual responses more generally in heterosexual women, although not necessarily in homosexual women.     

Do homosexual persons use health care services more frequently than heterosexual persons: findings from a Dutch population survey

Use of health care services has been suggested to be lower among homo- or bisexual persons than among heterosexual persons, due to a lack of trust in the health care system. However, population-based studies on differences in health care utilization according to sexual orientation are scarce. The purpose of the current study was to explore differences in health care utilization and confidence in health care between heterosexual, bisexual and homosexual persons. A survey of a random sample of patients of Dutch general practices (n = 9684) gathered data on socio-demographic variables, sexual orientation, health status, confidence in health care and health care utilization. Differences in health care utilization between homo- or bisexual persons and heterosexual persons were analyzed with logistic regression analysis, in which we statistically adjusted for socio-demographics and health status. Reported health was lower among homosexual men and women as compared to heterosexual persons. There were no sexual orientation-related differences in confidence in health care. Controlling for health status, it appeared that gay men more frequently used mental and somatic health care than heterosexual men, and that lesbian or bisexual women more frequently used mental health care than heterosexual women. We found a higher rate of health care use among homosexual and bisexual persons as compared to heterosexual persons, that could only be partly explained by differences in health status. To gain a better understanding of our findings, data on the predisposition to use health services among homosexual and bisexual men and women is needed.     

Correlates of sexual orientation in the German Democratic Republic

From 5469 participants of a sexual inquiry in the German Democratic Republic, 90 homosexual and 107 heterosexual women and men were selected, aged 16–30. A comparison was made concerning aspects of leisure time and sexual life. Some differences appear with regard to leisure time between homosexual and heterosexual women and men. The importance of love and sexuality is as great for young homosexuals as it is for young heterosexuals, but the mode and quantity of their specific sexual activities differ. Homosexual women appear to be more sexually active than heterosexual women on some study parameters.     

Mate Retention Behavior of Men and Women in Heterosexual and Homosexual Relationships

Comparing the behavior of heterosexual and homosexual persons can provide insight into the origins of heterosexual sex differences in psychology. Evidence indicates that, aside from sexual partner preference, the mating psychology of homosexual men is sex-typical whereas that of homosexual women tends to be more sex-atypical. The current study examined one aspect of mating psychology, mate retention behavior, and tested whether homosexual men and women were sex-typical or sex-atypical for those mate retention tactics where heterosexual men and women differed. Men and women in heterosexual and homosexual relationships were asked to provide information regarding their partners' mate retention behavior by using the Mate Retention Inventory Questionnaire. Heterosexual men and women differed significantly for six of the 19 mate retention tactics considered. With respect to the six mate retention tactics where heterosexual sex differences existed, homosexual men behaved in a sex-typical manner for five of the tactics, whereas homosexual women behaved in a sex-atypical manner for all six tactics. We discuss the significance of these findings for explaining the origins of the mate retention behavior of heterosexual men and women. In addition, we consider what the pattern of sex-typical and sex-atypical mating psychology among homosexual men and women, respectively, suggests in regard to sex differences in the development of mating psychology and the development of homosexual persons.     

Coping Styles as Mediator of Sexual Orientation-Related Health Differences

The higher prevalence of health problems in homosexual compared to heterosexual populations is usually understood as a consequence of minority stress. We hypothesized that differential rates of health problems also could result from sexual orientation-related differences in coping styles. We explored this using data collected in a general population-based study (N = 9684) via face-to-face interviews. A higher prevalence of both mental and physical health problems, as assessed with individual questions, the GHQ-12, and checklists, was observed in homosexual compared to heterosexual men and women. Coping style was related to sexual orientation in men, but not in women. Compared to heterosexual men, homosexual men more strongly applied emotion-oriented and avoidance coping strategies. Emotion-oriented coping mediated the differences in mental and physical health between heterosexual and homosexual men. Findings suggest the importance of further exploration of the development and use of emotion-oriented and avoidance coping by homosexual men.     

Can Some Gay Men and Lesbians Change Their Sexual Orientation? 200 Participants Reporting a Change from Homosexual to Heterosexual Orientation

Position statements of the major mental health organizations in the United States state that there is no scientific evidence that a homosexual sexual orientation can be changed by psychotherapy, often referred to as reparative therapy. This study tested the hypothesis that some individuals whose sexual orientation is predominantly homosexual can, with some form of reparative therapy, become predominantly heterosexual. The participants were 200 self-selected individuals (143 males, 57 females) who reported at least some minimal change from homosexual to heterosexual orientation that lasted at least 5 years. They were interviewed by telephone, using a structured interview that assessed same sex attraction, fantasy, yearning, and overt homosexual behavior. On all measures, the year prior to the therapy was compared to the year before the interview. The majority of participants gave reports of change from a predominantly or exclusively homosexual orientation before therapy to a predominantly or exclusively heterosexual orientation in the past year. Reports of complete change were uncommon. Female participants reported significantly more change than did male participants. Either some gay men and lesbians, following reparative therapy, actually change their predominantly homosexual orientation to a predominantly heterosexual orientation or some gay men and women construct elaborate self-deceptive narratives (or even lie) in which they claim to have changed their sexual orientation, or both. For many reasons, it is concluded that the participants' self-reports were, by-and-large, credible and that few elaborated self-deceptive narratives or lied. Thus, there is evidence that change in sexual orientation following some form of reparative therapy does occur in some gay men and lesbians.     

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.     

Interaction of older brothers and sex-typing in the prediction of sexual orientation in men

Numerous studies indicate that homosexual men have, on average, more older brothers than do heterosexual men. One explanation of the older brother effect comes from D. J. Bem (1996), who argued that an increased number of older brothers in homosexual men can result if older brothers enhance a feminine boy's sense of being different from (and hence his attraction to) other males. Thus, he argued that an interaction between older brothers and sex-typing will occur, such that when a boy is high in femininity, number of older brothers may strongly predict a homosexual orientation; and when a boy is low in femininity, number of older brothers may not or may only weakly predict a homosexual orientation. In this study, the relations among sibling characteristics (e.g., older brothers), childhood sex-typing, and sexual orientation were examined using a database of a large sample of homosexual and heterosexual men (N > 1,000) archived at the Kinsey Institute (A. P. Bell, M. S. Weinberg, & S. K. Hammersmith, 1981a). No significant Older Brother × Sex-Typing interaction effect was observed. These results join other recent evidence that postnatal (e.g., learning/environmental) mechanisms probably do not underlie the older brother effect in men.     

Psychophysiological assessment of sex offenders in a security hospital

A study on the sexual orientation and responsiveness of sexual offenders in a maximum security hospital who had been referred to the Psychology Department for sexual assessment is described. Correlations between felt sexual arousal ratings and penis diameter increase were calculated to assess validity, but a high proportion of detained patients gave results which could be interpreted as indicating defensiveness or faking. Groups of sexual offenders (against women, girls, boys, and men), nonsexual attackers of women, and typical heterosexuals were compared on their profiles of response to films showing consenting adult heterosexual, adult homosexual, and boy homosexual activity, girl abduction, and girl rape. Groups did not differ on the consenting heterosexual activity film, but typical heterosexuals and nonsexual attackers of women showed significantly less response to the film of girl abduction (p<0.001) and rape (p<0.001] than did groups of sex offenders generally. This research was carried out while the authors were in the Special Hospital Research Unit at Broadmoor Hospital, Crowthorne, Berks. The views expressed in this article must not be taken as representing those of any Institution or Government Department.     

Shape Differences Between the Faces of Homosexual and Heterosexual Men

Previous studies have shown that homosexual men differ from heterosexual men in several somatic traits and lay people accurately attribute sexual orientation based on facial images. Thus, we may predict that morphological differences between faces of homosexual and heterosexual individuals can cue to sexual orientation. The main aim of this study was to test for possible differences in facial shape between heterosexual and homosexual men. Further, we tested whether self-reported sexual orientation correlated with sexual orientation and masculinity–femininity attributed from facial images by independent raters. In Study 1, we used geometric morphometrics to test for differences in facial shape between homosexual and heterosexual men. The analysis revealed significant shape differences in faces of heterosexual and homosexual men. Homosexual men showed relatively wider and shorter faces, smaller and shorter noses, and rather massive and more rounded jaws, resulting in a mosaic of both feminine and masculine features. In Study 2, we tested the accuracy of sexual orientation judgment from standardized facial photos which were assessed by 80 independent raters. Binary logistic regression showed no effect of attributed sexual orientation on self-reported sexual orientation. However, homosexual men were rated as more masculine than heterosexual men, which may explain the misjudgment of sexual orientation. Thus, our results showed that differences in facial morphology of homosexual and heterosexual men do not simply mirror variation in femininity, and the stereotypic association of feminine looking men as homosexual may confound judgments of sexual orientation.