Interaction of fraternal birth order and handedness in the development of male homosexuality

  title={Interaction of fraternal birth order and handedness in the development of male homosexuality},
  author={Ray Blanchard and James M. Cantor and Anthony F Bogaert and S. Marc Breedlove and Lee Ellis},
  journal={Hormones and Behavior},

Figures and Tables from this paper

Sex Ratio of Older Siblings in Heterosexual and Homosexual, Right-Handed and Non-Right-Handed Men

It is suggested that both heterosexual and homosexual non-right-handers contribute to the older brothers × handedness ×-sexual orientation interaction.

Review and theory of handedness, birth order, and homosexuality in men

The maternal immune hypothesis might be extended or modified to account for the apparent interaction of older brothers and handedness, and two possibilities are considered: non- right-handed foetuses are insensitive to the presence of maternal anti-male antibodies, and mothers of non-right-handedfoetuses do not produce anti- male antibodies.

The Sex Ratio of Older Siblings in Non-Right-Handed Homosexual Men

This study tested the prediction, based on prior research, that non-right-handed homosexual men will report fewer than expected older brothers, and the results were significantly lower than the human sex ratio and significantly higher than the expected ratio.

Sexual orientation, handedness, sex ratio and fetomaternal tolerance-rejection.

A new explanation for sexual relationships, sexual orientation, handedness and sibling SR is proposed, where lesbian embryos could induce tolerance from mothers with anti-female factors, and non-right-handedness could induce maternal tolerance, or change the maternal compatibility of "gay" embryos.

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

There was evidence for a relationship among handedness, sexual orientation, and CGN, and mediation analysis revealed that handedness was associated with sexual orientation directly and also indirectly through the mediating factor of CGN.

Birth Order, Sibling Sex Ratio, Handedness, and Sexual Orientation of Male and Female Participants in a BBC Internet Research Project

The results yielded some evidence confirming prior findings that non-right-handedness is associated with homosexuality in men and women, that older brothers increase the odds of homosexuals in men, and that the effect of older brothers on sexual orientation is limited to right-handed men.

Fraternal Birth Order, Handedness, and Sexual Orientation in a Chinese Population

The results showed that homosexual women are more likely to be non-right-handed than heterosexual women, regardless of how sexual orientation was defined, whereas bisexual women areMore likely to been non- right-handedthan heterosexual women whenSexual orientation was assessed via sexual attraction and sexual identity.

Extreme right-handedness, older brothers, and sexual orientation in men.

An elevated rate of extreme right-handedness was found in gay or bisexual men relative to heterosexual men, and it was demonstrated that older brothers moderate the relationship between handedness and sexual orientation.

Fraternal Birth Order, Family Size, and Male Homosexuality: Meta-Analysis of Studies Spanning 25 Years

The fraternal birth order effect is the tendency for older brothers to increase the odds of homosexuality in later-born males and in homosexual subjects with masculine versus feminine gender identities is compared and evidence for the reliability of the effect was consistent.

Interaction of birth order, handedness, and sexual orientation in the Kinsey interview data.

The results demonstrated that handedness moderates the relationship between older brothers and sexual orientation, and suggest that biological explanations of men's sexual orientation are likely relevant across time, as the Kinsey data comprise an older cohort relative to modern samples.



Birth order and ratio of brothers to sisters in transsexuals

  • R. Green
  • Psychology
    Psychological Medicine
  • 2000
Hypotheses explaining the extension of prior findings to this large sample of transsexual males include a progressive maternal immunization to the male foetus either through the H-Y antigen or protein-bound testosterone or alterations in foetal androgen levels in successive pregnancies, all modifying male psychosexual development.

Homosexuality in men and number of older brothers.

The range of possible theories of the birth order phenomenon is restricted to those that can explain not only why older brothers increase the probability of homosexuality in later-born males but also why older sisters neither enhance this effect nor counteract it.

Fraternal Birth Order and Sexual Orientation in Pedophiles

It is shown that fraternal birth order correlates with homosexuality in pedophiles, just as it does in men attracted to physically mature partners, and may prove the first identified universal factor in homosexual development.

Quantitative and theoretical analyses of the relation between older brothers and homosexuality in men.

Sexual orientation and handedness in men and women: a meta-analysis.

The results support the notion that sexual orientation in some men and women has an early neurodevelopmental basis, but the factors responsible for the handedness-sexual orientation association require elucidation.

Handedness, Sexual Orientation, and Gender-Related Personality Traits in Men and Women

  • R. Lippa
  • Psychology
    Archives of sexual behavior
  • 2003
Rates of non–right-handedness were virtually identical for heterosexual men and women, suggesting that sex differences in handedness may result from higher rates of homosexuality in men, and within groups, handedness showed a number of weak but statistically significant associations with sex-typed occupational preferences, self–ascribed masculinity, and self-ascribed femininity, but not with instrumentality or expressiveness.

Familiality of female and male homosexuality

Results were most consistent with the possibility that similar familial factors influence male and female sexual orientation, but further work is needed using large samples and more careful methods before the degree of cofamiliality ofmale and female homosexuality can be resolved definitively.

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

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), which is most likely to occur in men with a high number of older brothers and shorter stature.

Fraternal Birth Order and the Maternal Immune Hypothesis of Male Homosexuality

The maternal immune hypothesis is consistent with a variety of evidence, including the apparent irrelevance of older sisters to the sexual orientation of later born males, the probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-y antigen on the reproductive performance of subsequent male offspring.