Sexual-orientation-related differences in verbal fluency.

This study examined the performance of 60 heterosexual men, 60 gay men, 60 heterosexual women, and 60 lesbians on 3 tests of verbal fluency known to show gender differences: letter, category, and synonym fluency. Gay men and lesbians showed opposite-sex shifts in their profile of scores. For letter fluency, gay men outperformed all other groups; lesbians showed the lowest scores. For category fluency, gay men and heterosexual women jointly outperformed lesbians and heterosexual men. Finally, gay men outperformed all other groups on synonym fluency, whereas lesbians and heterosexual men performed similarly. A difference between heterosexual men and women was demonstrated on category and synonym fluency only. The findings implicate within-sex differences in the functioning of the prefrontal and temporal cortices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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 1 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.     

Within-group differences in sexual orientation and identity.

The purpose of this investigation was to examine within-group differences among self-identified sexual orientation and identity groups. To understand these within-group differences, 2 types of analysis were conducted. First, a sample of 2,732 participants completed the Sexual Orientation and Identity Scale. Cluster analyses were used to identify 3 types of bisexual women, 3 types of bisexual men, 2 types of heterosexual women, and 2 types of gay men. Lesbians and heterosexual men were clustered into singular groupings. In addition, a subsample of 838 participants also completed measures of sexual identity development and lesbian, gay, and bisexual knowledge and attitudes. Within-group differences were found for bisexual men and women, gay men, and heterosexual women along these dimensions. Findings supported the existence of distinct subgroups of bisexual men, bisexual women, gay men, and heterosexual women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective sexual orientation-related differences in object location memory.

The present study examined sexual orientation-related differences in object location memory by using 3 object arrays (testing object exchange, object shift, and novel objects conditions) and 1 metric positional memory array. Heterosexual women and homosexual men significantly outperformed heterosexual men in all 3 object arrays. However, there were no group differences in metric positional memory. Heterosexual males expectedly outperformed the other groups in spatial perception (Judgment of Line Orientation; A. L. Benton, K. D. Hamsher, N. R. Varney, & O. Spreen, 1983). Regression modeling revealed that sexual orientation and spatial perception predicted object exchange performance, whereas recalled childhood gender nonconformity, a robust developmental marker of adult sexual orientation, predicted object shift and novel object performance alone. A measure ascribed to the actions of prenatal androgens, the 2nd to 4th finger length ratio, did not predict object location memory. These data may limit possible developmental pathways for sexual variation in selective forms of spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medical therapy of active Crohn''s disease

To elucidate neurobiological factors related to gender and sexual orientation, event-related brain potentials of 20 heterosexual (HT) men, 20 HT women, 20 homosexual (HM) men, and 20 HM women were examined for neurophysiological differences. Cognitive tasks which typically elicit sex differences were administered. A mental rotation (MR) task assessed spatial ability, and a divided-visual-field lexical-decision/semantic monitoring task (LD/SM) assessed verbal ability and relative degrees of language lateralization. Slow wave activity recorded during MR was greater for HT men than for HT women and gay men. N400 asymmetries recorded during the LD/SM task revealed differences between men and women, but no intrasex differences.     

Sexual orientation and childhood gender nonconformity: Evidence from home videos.

Homosexual adults tend to be more gender nonconforming than heterosexual adults in some of their behaviors, feelings, and interests. Retrospective studies have also shown large differences in childhood gender nonconformity, but these studies have been criticized for possible memory biases. The authors studied an indicator of childhood gender nonconformity not subject to such biases: childhood home videos. They recruited homosexual and heterosexual men and women (targets) with videos from their childhood and subsequently asked heterosexual and homosexual raters to judge the gender nonconformity of the targets from both the childhood videos and adult videos made for the study. Prehomosexual children were judged more gender nonconforming, on average, than preheterosexual children, and this pattern obtained for both men and women. This difference emerged early, carried into adulthood, and was consistent with self-report. In addition, targets who were more gender nonconforming tended to recall more childhood rejection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Specific Sexual Orientation-Related Difference in Navigation Strategy.

During spatial navigation, women typically navigate an environment using a landmark strategy, whereas men typically use an orientation strategy. To examine the as yet unknown effects of sexual orientation on these normative sex differences, this study required 80 healthy heterosexual and homosexual adult men and women to provide directions from experimental maps for 4 routes. The frequency and type of strategy used by each participant were computed. Expected sex differences were demonstrated, and a robust cross-sex shift was shown by homosexual men in using landmarks. This remained after controlling for differences in mental rotation, directional sense, and general intelligence. The findings may limit the number of putative neurodevelopmental pathways responsible for sex differences in navigation strategy utility. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental Instability Is Associated With Neurocognitive Performance in Heterosexual and Homosexual Men, but Not in Women.

Little is known about the neurodevelopmental nature of human cognitive abilities. This investigation presents evidence consistent with a hypothesis that interindividual and within-sex cognitive variations are associated with vulnerabilities to environmental sources of developmental stress. A large sample of healthy heterosexual and homosexual men and women (N=240) completed a series of visuospatial and verbal tests. A composite fluctuating asymmetry (FA) measure was computed from the lengths of the finger digits. In heterosexual men, higher FA scores were associated with poorer line orientation judgment; and in homosexual men, with poorer verbal fluency and perceptual speed. No associations were found in heterosexual or homosexual women. These results suggest that developmental instability is linked to neurocognitive integrity in men, but not in women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual orientation-related differences in prepulse inhibition of the human startle response.

Prepulse inhibition (PPI) refers to a reduction in the startle response to a strong sensory stimulus when this stimulus is preceded by a weaker stimulus--the prepulse. PPI reflects a nonlearned sensorimotor gating mechanism and also shows a robust gender difference, with women exhibiting lower PPI than men. The present study examined the eyeblink startle responses to acoustic stimuli of 59 healthy heterosexual and homosexual men and women. Homosexual women showed significantly masculinized PPI compared with heterosexual women, whereas no difference was observed in PPI between homosexual and heterosexual men. These data provide the first evidence for within-gender differences in basic sensorimotor gating mechanisms and implicate the known neural substrates of PPI in human sexual orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dermatoglyphic asymmetry and sexual orientation in men.

Dermal ridges on the fingertips are formed early in fetal life and remain unchanged throughout the life span. The researchers examined dermatoglyphic characteristics (total ridge count and directional ridge asymmetry) in homosexual and heterosexual men. There was no difference between the 2 groups of men in total ridge count, but more gay men demonstrated leftward asymmetry than did nongay men. Although this effect was not accounted for by differences in hand preference, an association was observed between leftward dermatoglyphic asymmetry and an increased incidence of adextrality in homosexual men, but not in heterosexual men. These findings are consistent with a biological contribution to sexual orientation and indicate that such an influence may occur early in prenatal life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gender and sexual orientation differences in sexual response to sexual activities versus gender of actors in sexual films.

In this study, the authors investigated the hypothesis that women's sexual orientation and sexual responses in the laboratory correlate less highly than do men's because women respond primarily to the sexual activities performed by actors, whereas men respond primarily to the gender of the actors. The participants were 20 homosexual women, 27 heterosexual women, 17 homosexual men, and 27 heterosexual men. The videotaped stimuli included men and women engaging in same-sex intercourse, solitary masturbation, or nude exercise (no sexual activity); human male-female copulation; and animal (bonobo chimpanzee or Pan paniscus) copulation. Genital and subjective sexual arousal were continuously recorded. The genital responses of both sexes were weakest to nude exercise and strongest to intercourse. As predicted, however, actor gender was more important for men than for women, and the level of sexual activity was more important for women than for men. Consistent with this result, women responded genitally to bonobo copulation, whereas men did not. An unexpected result was that homosexual women responded more to nude female targets exercising and masturbating than to nude male targets, whereas heterosexual women responded about the same to both sexes at each activity level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is homophobia associated with homosexual arousal?

The authors investigated the role of homosexual arousal in exclusively heterosexual men who admitted negative affect toward homosexual individuals. Participants consisted of a group of homophobic men (n?=?35 ) and a group of nonhomophobic men (n?=?29); they were assigned to groups on the basis of their scores on the Index of Homophobia (W. W. Hudson & W. A. Ricketts, 1980). The men were exposed to sexually explicit erotic stimuli consisting of heterosexual, male homosexual, and lesbian videotapes, and changes in penile circumference were monitored. They also completed an Aggression Questionnaire (A. H. Buss & M. Perry, 1992). Both groups exhibited increases in penile circumference to the heterosexual and female homosexual videos. Only the homophobic men showed an increase in penile erection to male homosexual stimuli. The groups did not differ in aggression. Homophobia is apparently associated with homosexual arousal that the homophobic individual is either unaware of or denies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural correlates of sexual arousal in homosexual and heterosexual men.

Men exhibit much higher levels of genital and subjective arousal to sexual stimuli containing their preferred sex than they do to stimuli containing only the nonpreferred sex. This study used event-related functional magnetic resonance imaging to investigate how this category-specific pattern would be reflected in the brains of homosexual (n = 11) and heterosexual (n = 11) men. Comparisons of activation to preferred sexual stimuli, nonpreferred sexual stimuli, and sports stimuli revealed large networks correlated with sexual arousal, spanning multiple cortical and subcortical areas. Both homosexual and heterosexual men exhibited category-specific arousal in brain activity. Within the amygdala, greater preference-related activity was observed in homosexual men, but it is unclear whether this is a cause or a consequence of their sexuality. In a subsequent analysis of regions hypothesized to support arousal, both participant groups demonstrated widespread increases in evoked activity for preferred stimuli. Aggregate data from these regions produced significant differences between stimulus types in 16 out of 22 participants. Significant activational differences matched reported sexual orientation in 15 of these 16 participants, representing an advance in psychophysiological measures of arousal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Education and MMPI Mf scores in homosexual and heterosexual males.

Investigated the relationship between MMPI Mf, Hsx, and education in 64 heterosexual and 49 homosexual men. Ss were obtained from a variety of sources, were generally older than college students, and averaged between 2 and 3 yr. of college education. The groups differed significantly on Mf, Hsx, and Kinsey self-ratings. MMPI scale differences were found on F, K, D, Pd, Pa, Pt, Sc, and Si. Correlations of .20 and .27 were found between education and the Mf and Hsx scores. Data indicate that Mf was a better discriminator between the homosexual and heterosexual groups than Hsx, and was less contaminated by educational bias. It is concluded that the relationship between educational level and Mf appears to be more complex than generally assumed. (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age preferences and mate choice among homosexuals and heterosexuals: A case for modular psychological mechanisms.

Age preferences expressed by homosexuals and heterosexuals in 783 singles ads were compared. In line with earlier cross-cultural findings, heterosexual women at all ages tend to prefer men from their own age to several years older. Heterosexual men change with age; young men show an interest in both older and younger women, but older men express progressively stronger interest in women younger than themselves. Homosexual men's preferences were very similar to those of heterosexual men and homosexual women showed a pattern somewhat between that of heterosexual women and men. Results combine with previous literature to suggest that homosexual choice is not a simple and general reversal of heterosexual roles, and fit with an emerging view that sexual behavior is controlled by a number of independently evolved psychological mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Childhood sex-typed behavior and sexual orientation: A conceptual analysis and quantitative review.

This article reviewed research examining the association between childhood sex-typed behavior and sexual orientation. Prospective studies suggest that childhood cross-sex-typed behavior is strongly predictive of adult homosexual orientation for men; analogous studies for women have not been performed. Though methodologically more problematic, retrospective studies are useful in determining how many homosexual individuals displayed cross-sex behavior in childhood. The relatively large body of retrospective studies comparing childhood sex-typed behavior in homosexual and heterosexual men and women was reviewed quantitatively. Effect sizes were large for both men and women, with men's significantly larger. Future research should elaborate the causes of the association between childhood sex-typed behavior and sexual orientation and identify correlates of within-orientation differences in childhood sex-typed behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hair whorl direction and sexual orientation in human males.

Hair whorl direction is a somatic feature that is organized early during neurodevelopment and unlikely to be influenced by social factors. This study aimed to replicate a widely reported association by A. J. S. Klar (2003) between counterclockwise hair whorl direction and homosexuality in men, using more objective methodology. The authors took digital photographs of parietal surface hair whorls from 100 heterosexual men and 100 homosexual men who were predominantly right-handed. These images were rated for clockwise and counterclockwise direction (for which no more than 1 hair whorl was present) by 2 raters unaware of sexual orientation. The authors found no significant difference between heterosexual and homosexual men in hair whorl direction, but the authors did replicate the fraternal birth order effect (more older brothers for homosexual men). Number of older sisters was positively correlated with counterclockwise hair whorls in heterosexual men. These data were discussed in relation to prenatal factors assumed to play a role in the neurodevelopment of male homosexuality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Homophobia and physical aggression toward homosexual and heterosexual individuals.

This study examined the relationship between homophobia (defined as self-reported negative affect, avoidance, and aggression toward homosexuals) and homosexual aggression. Self-identified heterosexual college men were assigned to homophobic (n?=?26) and nonhomophobic (n?=?26) groups on the basis of their scores on the Homophobia Scale (HS; L. W. Wright, H. E. Adams, & J. A. Bernat, 1999). Physical aggression was examined by having participants administer shocks to a fictitious opponent during a competitive reaction time (RT) task under the impression that the study was examining the relationship between sexually explicit material and RT. Participants were exposed to a male homosexual erotic videotape, their affective reactions were assessed, and they then competed in the RT task against either a heterosexual or a homosexual opponent. The homophobic group reported significantly more negative affect, anxiety, and anger-hostility after watching the homosexual erotic videotape than did the nonhomophobic group. Additionally, the homophobic group was significantly more aggressive toward the homosexual opponent, but the groups did not differ in aggression toward the heterosexual opponent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contingent negative variation (CNV) and erotic preference in self-declared homosexuals and in child sex offenders

Contingent negative variation (CNV) was recorded bilaterally from central electrodes using a "match/mismatch" paradigm in (Study 1) samples of heterosexual men (N = 6), gay men (N = 10) and lesbian women (N = 14) and (Study 2) in samples of child sex offenders (N = 34) and heterosexual control men (N = 19). Sexual orientation was assessed using the Multidimensional Scale of Sexuality (MSS) and the Human Sexuality Questionnaire (HSQ). Separate CNV averages were formed for each condition of stimulation: for Study 1, slides of adult male and female nudes; for Study 2, slides of child, pubescent and adult male and female nudes. Penile plethysmographic (PPG) data were also obtained from 15 of the child sex offender sample while they viewed stimuli of the same categories as were used in the CNV recording. On the basis of their PPG responses to children, child sex offenders were classified as either "pedophiles" or "non-pedophiles". In Study 1 significant Group x Sex (of slide) and Group x Electrode interactions indicated that: (i) heterosexual men (but neither homosexual group) showed significantly larger CNVs to female than to male slides; (ii) both homosexual groups showed significantly asymmetrical (R > L) CNVs. In Study 2, controls showed significantly greater CNVs to adult females than to both adult males and female children. Child sex offenders showed no significant differences in CNV to male and female slides for any age. "Non-pedophiles" showed significantly larger CNVs to female adults than to female children, but "pedophiles" did not. It is concluded that CNV has promise as a measure of both deviant and non-deviant sexual preference.     

The interaction of fraternal birth order and body size in male sexual orientation.

A late fraternal birth order has been demonstrated numerous times in homosexual men. Body size has been less studied with regard to the development of sexual orientation and has demonstrated contradictory results. In this research, the relations among fraternal birth order, body size, and sexual orientation were examined in a Canadian sample of homosexual and heterosexual men. An interaction between fraternal birth order and height was observed, with a homosexual orientation most likely to occur in men with a high number of older brothers and shorter stature. No significant interactive effects were observed for weight. The results suggest that the mechanism underlying the fraternal birth order phenomenon has an effect on physical development that lasts and is detectable into adulthood (i.e., adult stature). (PsycINFO Database Record (c) 2010 APA, all rights reserved)