Sexual orientation related differences in spatial memory.

The purpose of this study was to investigate and extend previously reported sex differences in object location memory by comparing the performance of heterosexual and homosexual males and females. Subjects were 240 healthy, right-handed heterosexual and homosexual males and females. They were instructed to study 16 common, gender-neutral objects arranged randomly in an array and subsequently tested for object recall, object recognition and spatial location memory. Females recalled significantly more objects than males, although there were no group differences in object recognition. Decomposition of significant interactions between sex and sexual orientation on spatial location memory (controlling for differences in object recall, age and IQ) revealed that heterosexual females and homosexual males scored better than heterosexual males, and no different from each other. There were no differences between homosexual and heterosexual females. The findings suggest that homosexual males and heterosexual females encode, store and retrieve positional and relational information about spatial layouts similarly, pointing to within-sex variations in the neural architecture underlying spatial memory.     

Sexual orientation and neurocognitive ability: A meta-analysis in men and women

The cross-sex-shift hypothesis predicts that homosexual men and women will be similar in certain neurobehavioral traits to their opposite-sex counterparts. Accordingly, it predicts that homosexual men should perform in the direction of heterosexual women, and homosexual women in the direction of heterosexual men, on neurocognitive tests that show normative sex differences. We conducted a meta-analysis on the relationship between sexual orientation and cognitive performance, and tested the effects of potential moderating variables separately by sex. A total of 106 samples and 254,231 participants were included. The meta-analysis revealed that homosexual men performed like heterosexual women in both male-favouring (e.g., spatial cognition) and female-favouring (e.g., verbal fluency) cognitive tests, while homosexual women performed like heterosexual men only in male-favouring tests. The magnitude of the sexual orientation difference varied across cognitive domains (larger for spatial abilities). It was also larger in studies comparing exclusive heterosexuals with exclusive homosexuals compared to studies comparing exclusive heterosexuals with non-exclusive homosexuals for both sexes. The results may narrow down potential sites for sexual orientation-related neural differences.     

Fluctuating asymmetry, second to fourth finger length ratios and human sexual orientation

Sexual orientation in humans may be influenced by levels of prenatal sex steroids which canalise neurodevelopment along sex-typical (heterosexual) or sex-atypical (homosexual) lines. Some evidence for sexual-orientation-related differences in putative somatic markers of prenatal sex hormones supports this view. A competing theory asserts that human homosexuality is due to developmental instability (DI) because it represents a shift from the species-typical pattern of heterosexual orientation. Evidence for elevated rates of non-right handedness among homosexuals provides limited support for this account. The current study tested both theories by examining nine bilateral somatic traits in 120 healthy heterosexual and homosexual men and women in order to compute second to fourth finger length ratios (2D:4D), a measure ascribed to levels of prenatal sex steroids, and fluctuating asymmetry (FA), a measure of DI. Homosexual men and women had significantly lower right hand 2D:4D ratios (even after controlling for handedness, height and weight differences) in comparison to heterosexuals, but sexual orientation did not relate to composite FA scores. The findings constrain the number of possible neurodevelopmental pathways responsible for sexual orientation in humans.     

Neuropsychological development of cognitive abilities: a new research strategy and some preliminary evidence for a sexual orientation model

The organizing action that prenatal sex hormones exert on the brain has been implicated in the aetiology of sex differences in cognitive abilities and cerebral asymmetries. Prenatal sex hormones are known to determine neuroendocrine responses and subsequent adult sexual behaviour in nonhuman animals and these hormones may also influence human sexual orientation. To unify these observations, we elaborate a sexual orientation model of neuropsychological development which predicts that sex differences in neuroendocrine responses, cerebral asymmetries, and cognitive abilities are related to sexual orientation rather than to sex per se. A common problem in the study of sex differences is that biological and sociocultural explanations are confounded. The sexual orientation model suggests a new research strategy, the comparison of homosexual and heterosexual groups, for which explanations in terms of sociocultural factors would be more difficult to sustain. The available evidence supports the model: In terms of a neuroendocrine response, cerebral asymmetry, and cognitive abilities, homosexual males resemble heterosexual females rather than heterosexual males. Our conclusions lead to questions that further research in this area should address, and to a consideration of problems which such research may have to face.     

A crossover interaction between sex, sexual orientation, and handedness

The distribution of handedness scores was analysed in 1414 heterosexual, bisexual, and homosexual men and women. Hand preference was assessed by a questionnaire that distinguishes consistently right-handed from partially or completely left-handed individuals, and sexual orientation was measured by the Kinsey scales. As expected from population-based studies, heterosexual men were, on average, more left-handed than heterosexual women. By contrast, gay men were more right-handed than lesbians or heterosexual men, and lesbians were more left-handed than gay men or heterosexual women. This crossover interaction suggests that a common variable influences sex, sexual orientation, and hand preference.     

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

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.     

Cerebral sex dimorphism and sexual orientation

The neurobiology of sexual orientation is frequently discussed in terms of cerebral sex dimorphism (defining both functional and structural sex differences). Yet, the information about possible cerebral differences between sex‐matched homo and heterosexual persons is limited, particularly among women. In this multimodal MRI study, we addressed these issues by investigating possible cerebral differences between homo and heterosexual persons, and by asking whether there is any sex difference in this aspect. Measurements of cortical thickness (Cth), subcortical volumes, and functional and structural resting‐state connections among 40 heterosexual males (HeM) and 40 heterosexual females (HeF) were compared with those of 30 homosexual males (HoM) and 30 homosexual females (HoF). Congruent with previous reports, sex differences were detected in heterosexual controls with regard to fractional anisotropy (FA), Cth, and several subcortical volumes. Homosexual groups did not display any sex differences in FA values. Furthermore, their functional connectivity was significantly less pronounced in the mesial prefrontal and precuneus regions. In these two particular regions, HoM also displayed thicker cerebral cortex than other groups, whereas HoF did not differ from HeF. In addition, in HoM the parietal Cth showed “sex‐reversed” values, not observed in HoF. Homosexual orientation seems associated with a less pronounced sexual differentiation of white matter tracts and a less pronounced functional connectivity of the self‐referential networks compared to heterosexual orientation. Analyses of Cth suggest that male and female homosexuality are not simple analogues of each other and that differences from heterosexual controls are more pronounced in HoM.     

Performance Differences Between Adult Heterosexual and Homosexual Men on the Digit-Symbol Substitution Subtest of the WAIS-R

Previous evidence suggests that sexual orientation influences performance on a number of cognitive functions known to be sexually dimorphic. This investigation examined the performance of 240 right-handed subjects (60 heterosexual men, 60 homosexual men, 60 heterosexual women and 60 homosexual women) on one of the most commonly used neuropsychological tests to show normative sex differences, the Digit-Symbol Substitution test of the WAIS-R. Analysis of scaled Digit-Symbol scores revealed that heterosexual women and homosexual men outperformed heterosexual men. The magnitude of these differences were modest by standard criteria. No differences were found between heterosexual and homosexual women. The findings implicate within-sex variation in one test that relies on intact executive function.     

Performance differences between adult heterosexual and homosexual men on the Digit-Symbol Substitution subtest of the WAIS-R

Previous evidence suggests that sexual orientation influences performance on a number of cognitive functions known to be sexually dimorphic. This investigation examined the performance of 240 right-handed subjects (60 heterosexual men, 60 homosexual men, 60 heterosexual women and 60 homosexual women) on one of the most commonly used neuropsychological tests to show normative sex differences, the Digit-Symbol Substitution test of the WAIS-R. Analysis of scaled Digit-Symbol scores revealed that heterosexual women and homosexual men outperformed heterosexual men. The magnitude of these differences were modest by standard criteria. No differences were found between heterosexual and homosexual women. The findings implicate within-sex variation in one test that relies on intact executive function.     

Sexual orientation-related differences in allocentric spatial memory tasks

Spatial memory in mammals, including humans, appears highly sexually dimorphic. The present investigation sought to examine if spatial learning and spatial memory in humans is also linked to sexual orientation. This was achieved by using virtual reality versions of two classic paradigms developed in animal models of hippocampal functioning, the Morris Water Maze (MWM) and Radial Arm Maze (RAM). Here, we show that in contrast to heterosexual men, and in congruence with heterosexual women, homosexual men displayed significantly greater search latencies (spatial learning) during a virtual Morris Water Maze. During a virtual 8-arm Radial Arm Maze, heterosexual males had significantly shorter search latency than heterosexual females, and did not differ from homosexual males. Statistical modeling revealed that variations in neurodevelopmental markers previously associated with human sexual orientation (2nd to 4th finger length ratios and older fraternal siblings) differentially predicted MWM probe trial performance and RAM search latencies only. These data may limit the number of possible neurodevelopmental pathways responsible for sexual variation in components of spatial learning and memory.     

Relationship history and relationship attitudes in gay males and lesbians: attachment style and gender differences

OBJECTIVE: The objective of the present study was to assess the applicability of attachment theory to the relationships of gay males and lesbians, with particular emphasis on parental relationships, relationship satisfaction, sexual attitudes and 'coming out' as being homosexual. METHODS: Gay males (n = 77) and lesbians (n = 100) completed questionnaires assessing attachment style, working models of attachment, early relationships with parents and relationship history, status and functioning. A comparison sample of heterosexual participants completed measures of attachment style and relationship history. RESULTS: Relative frequencies of attachment styles were similar for homosexual and heterosexual samples. Contrary to previous research using largely heterosexual respondents, no link between early parenting and attachment style was found. However, homosexual males reported more positive early relationships with mothers than did females. Associations of attachment style with working models, relationship variables and sexual attitudes largely supported those based on heterosexual samples. Gender and attachment style differences were found in reported effects of 'coming out' on relationships with parents. CONCLUSIONS: Overall, the results suggest that insecure attachment may not be over-represented in gay and lesbian samples, but that insecurity is associated with less relationship satisfaction and with problems related to the disclosure of sexual orientation. The implications of these findings for research and clinical practice are addressed.     

Brain response to visual sexual stimuli in heterosexual and homosexual males

Although heterosexual and homosexual individuals clearly show differences in subjective response to heterosexual and homosexual sexual stimuli, the neurobiological processes underlying sexual orientation are largely unknown. We addressed the question whether the expected differences in subjective response to visual heterosexual and homosexual stimuli may be reflected in differences in brain activation pattern. Twenty-four healthy male volunteers, 12 heterosexuals and 12 homosexuals, were included in the study. BOLD signal was measured while subjects were viewing erotic videos of heterosexual and homosexual content. SPM02 was used for data analysis. Individual sexual arousal was assessed by subjective rating. As compared to viewing sexually neutral videos, viewing erotic videos led to a brain activation pattern characteristic for sexual arousal in both groups only when subjects were viewing videos of their respective sexual orientation. Particularly, activation in the hypothalamus, a key brain area in sexual function, was correlated with sexual arousal. Conversely, when viewing videos opposite to their sexual orientation both groups showed absent hypothalamic activation. Moreover, the activation pattern found in both groups suggests that stimuli of opposite sexual orientation triggered intense autonomic response and may be perceived, at least to some extent, as aversive.     

A cognitive profile of homosexual men compared to heterosexual men and women

Matched groups of homosexual men, heterosexual men, and heterosexual women (n=38 per group) were tested on three measures of spatial ability and two measures of fluency that typically reveal sex differences. For the three spatial tests and one of the fluency tests, the mean performance of homosexual men fell between those of the heterosexual men and women. The pattern of cognitive skills of homosexual men was different from that of heterosexual men: homosexual men had lower spatial ability relative to fluency. The cognitive pattern of homosexual men was not significantly different from that of heterosexual women. In addition, the results suggest that homosexual men classified on the basis of hand preference may form two subgroups that differ in cognitive pattern. These findings are compatible with the hypothesis that there is a neurobiological factor related to sexual differentiation in the etiology of homosexuality.     

Biosocial factors, sexual orientation and neurocognitive functioning

It has been proposed that sexual orientation related differences in cognitive performance are either due to the actions of prenatal factors early in development or the influence of gender role learning. This study examined the performance of 240 healthy, right-handed heterosexual and homosexual males and females (N = 60 per group) on a battery of cognitive tasks comprising mental rotation, judgement of line orientation (JLO), verbal fluency, perceptual speed and object location memory. Measures were also taken of the psychological gender, birth order, sibling sex composition and the 2nd to 4th finger length ratios of the right and left hands. A series of stepwise regression analyses revealed that sex and sexual orientation were the strongest predictors of cognitive performance, with IQ also contributing considerable variance. Psychological gender (M/F scores) added a small, but significant, amount of variance to mental rotation and perceptual speed scores in addition to these main factors, but prenatal hormone related indices, such as 2nd to 4th finger ratios, birth order and sibling sex composition added no independent predictive power. These findings are discussed in relation to biosocial influences on cognitive differences between heterosexuals and homosexuals.     

Gender differences in memory processing of female facial attractiveness: evidence from event-related potentials

ABSTRACT

High rates of agreement in the judgment of facial attractiveness suggest universal principles of beauty. This study investigated gender differences in recognition memory processing of female facial attractiveness. Thirty-four Chinese heterosexual participants (17 females, 17 males) aged 18–24 years (mean age 21.63 ± 1.51 years) participated in the experiment which used event-related potentials (ERPs) based on a study-test paradigm. The behavioral data results showed that both men and women had significantly higher accuracy rates for attractive faces than for unattractive faces, but men reacted faster to unattractive faces. Gender differences on ERPs showed that attractive faces elicited larger early components such as P1, N170, and P2 in men than in women. The results indicated that the effects of recognition bias during memory processing modulated by female facial attractiveness are greater for men than women. Behavioral and ERP evidences indicate that men and women differ in their attentional adhesion to attractive female faces; different mating-related motives may guide the selective processing of attractive men and women. These findings establish a contribution of gender differences on female facial attractiveness during memory processing from an evolutionary perspective.     

Neural attention and evaluative responses to gay and lesbian couples

The goal of the current study was to examine whether differential neural attentional capture and evaluative responses for out-group homosexual relative to in-group heterosexual targets occur during social categorization. To this end, 36 heterosexual participants were presented with pictures of heterosexual and homosexual couples in a picture-viewing task that was designed to assess implicit levels of discomfort toward homosexuality and explicit evaluations of pleasantness toward the images. Neural activity in the form of electroencephalogram was recorded during the presentation of the pictures, and event-related potentials resulting from these stimuli were examined. Participants also completed questionnaires that assessed the degree to which they socialized with gays and lesbians. Results demonstrated that relative to straight couples, larger P2 amplitude was observed in response to gay but not to lesbian couples. However, both gay and lesbian couples yielded a larger late positive potential than straight couples. Moreover, the degree to which participants differentially directed early neural attention to out-group lesbian versus in-group straight couples was related to their familiarity with homosexual individuals. This work, which provides an initial understanding of the neural underpinnings of attention toward homosexual couples, suggests that differences in the processing of sexual orientation can occur as early as 200 ms and may be moderated by familiarity.     

Sexual behavior in adolescent and adult females with congenital adrenal hyperplasia.

As part of a comprehensive interview study, 34 female patients with congenital adrenal hyperplasia (CAH) plus 14 control sisters (ages 11-41 yr.) reported on their psychosexual development and sexual orientation (90 items). Fewer patients than sisters had ever experienced love relationships and sexual activities with male partners (p < 0.05 to 0.001). Twenty percent of the patients and none of the sisters wished for and/or had had homosexual relationships; in the patients > 21 yr 44% expressed this interest (p < 0.07). For most items, patients with the salt-wasting variant of CAH (SW) differed more clearly from the sisters than the simple-virilizing patients (SV). For two scales "indicating" homosexual (HOM) and heterosexual orientation (HET) and for two indices of HOM/HET differences), the patients also revealed relatively stronger homosexual and/or weaker heterosexual interests than the sisters (p < 0.05 to 0.001). Here, too, the SW/sister differences were more clear-cut. These results corroborate earlier reports on both delays in reaching psychosexual milestones and increased rates of bisexual/homosexual fantasies and experiences in CAH women.     

Evidence of familial nature of male homosexuality

We recruited 51 predominantly homosexual and 50 predominantly heterosexual men as index subjects for a family study of sexual orientation. The sexual orientation of siblings (115 sisters and 123 brothers) was ascertained in two ways: via interview with the index subjects and via interview of and/or mailed questionnaire to the siblings themselves. Index subjects' knowledge of the sexual orientation of their siblings was, for the most part, quite accurate. Moreover, heterosexual index men had about as many homosexual brothers as would be predicted given national prevalence figures for homosexuality, but homosexual index men had about four times as many homosexual brothers, although in both cases most brothers were heterosexual. There was no significant difference between the index groups in number of homosexual sisters. We conclude that there is a significant familial component to male homosexuality.     

Reversed temporal region asymmetries of P300 topography in left- and right-handed schizophrenic subjects.

The auditory P300 evoked potential was recorded in 36 subjects: left- (LH) and right-handed (RH) schizophrenic males and LH and RH normal controls. LH and RH normals showed no asymmetry in P300 scalp topography. LH and RH schizophrenics, however, showed lateralized asymmetries in temporal scalp regions: left < right P300 voltage asymmetry in RH schizophrenics and left > right P300 voltage asymmetry in LH schizophrenics. These data suggest that the schizophrenic pathology of P300 neural generators is lateralized according to handedness and provide the first evidence that LH and RH schizophrenics can be dissociated based on left-right voltage asymmetries in P300 topography. These findings further emphasize the need for control of handedness in P300 studies of schizophrenia.     

Same-sex sexual behavior and psychiatric disorders: findings from the Netherlands Mental Health Survey and Incidence Study (NEMESIS)

BACKGROUND: It has been suggested that homosexuality is associated with psychiatric morbidity. This study examined differences between heterosexually and homosexually active subjects in 12-month and lifetime prevalence of DSM-III-R mood, anxiety, and substance use disorders in a representative sample of the Dutch population (N = 7076; aged 18-64 years). METHODS: Data were collected in face-to-face interviews, using the Composite International Diagnostic Interview. Classification as heterosexual or homosexual was based on reported sexual behavior in the preceding year. Five thousand nine hundred ninety-eight (84.8%) of the total sample could be classified: 2.8% of 2878 men and 1.4% of 3120 women had had same-sex partners. Differences in prevalence rates were tested by logistic regression analyses, controlling for demographics. RESULTS: Psychiatric disorders were more prevalent among homosexually active people compared with heterosexually active people. Homosexual men had a higher 12-month prevalence of mood disorders (odds ratio [OR] = 2.93; 95% confidence interval [CI] = 1.54-5.57) and anxiety disorders (OR = 2.61; 95% CI = 1.44-4.74) than heterosexual men. Homosexual women had a higher 12-month prevalence of substance use disorders (OR = 4.05; 95% CI = 1.56-10.47) than heterosexual women. Lifetime prevalence rates reflect identical differences, except for mood disorders, which were more frequently observed in homosexual than in heterosexual women (OR = 2.41; 95% CI = 1.26-4.63). The proportion of persons with 1 or more diagnoses differed only between homosexual and heterosexual women (lifetime OR = 2.61; 95% CI = 1. 31-5.19). More homosexual than heterosexual persons had 2 or more disorders during their lifetimes (homosexual men: OR = 2.70; 95% CI = 1.66-4.41; homosexual women: OR = 2.09; 95% CI = 1.07-4.09). CONCLUSION: The findings support the assumption that people with same-sex sexual behavior are at greater risk for psychiatric disorders.