A relationship between handedness and sexual orientation has been suggested by a number of researchers, who report that heterosexual individuals are somewhat more likely to be right-handed than are homosexual individuals. The relationship between

handedness In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to and causing it to be stronger, faster or more Fine motor skill, dextrous. The other hand, comparatively often the weaker, less dext ...

and

sexual orientation Sexual orientation is an enduring personal pattern of romantic attraction or sexual attraction (or a combination of these) to persons of the opposite sex or gender, the same sex or gender, or to both sexes or more than one gender. Patterns ar ...

has been suggested within both sexes and may reflect the biological

etiology Etiology (; alternatively spelled aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek word ''()'', meaning "giving a reason for" (). More completely, etiology is the study of the causes, origins ...

; work by

Ray Blanchard Ray Milton Blanchard III ( ; born October 9, 1945) is an American-Canadian sexologist who researches pedophilia, sexual orientation and Transgender, gender identity. He has found that men with more older brothers are more likely to be gay than m ...

has linked the relationship to the

fraternal birth order effect Fraternal birth order, also known as the older brother effect, has been correlated with male sexual orientation, with a significant volume of research finding that the more older brothers a male has from the same mother, the greater the probabilit ...

, which suggests that a man with several older biological brothers is more likely to be homosexual. The psychologist Chris McManus and a team of researchers weighed in on the relationship to homosexuality and concluded:

Studies

Lalumière ''et al''., 2000 meta-analysis

Lalumière ''et al''. conducted a

meta-analysis Meta-analysis is a method of synthesis of quantitative data from multiple independent studies addressing a common research question. An important part of this method involves computing a combined effect size across all of the studies. As such, th ...

of 20 studies with a total of 6,987 homosexual and 16,423 heterosexual participants. They found that homosexual men had a 34% greater odds of not being right-handed, and homosexual women had a 91% greater odds (39% overall).

Williams ''et al''., 2000

In a study involving 382 men (278 homosexual and 104 heterosexual) no significant association emerged between handedness and sexual orientation.

Mustanski ''et al''., 2002 study

Mustanski ''et al''. examined sexual orientation and hand preference in a sample of 382 men (205 heterosexual; 177 homosexual) and 354 women (149 heterosexual; 205 homosexual). Although a significantly higher proportion of homosexual women was found to be left-handed compared to heterosexual women (18% vs. 10%), no significant differences were found between heterosexual and homosexual men with respect to hand preference.

Lippa, 2003 study

Lippa examined sexual orientation and handedness in a sample of 812 men (351 heterosexual; 461 homosexual) and 1,189 women (707 heterosexual; 472 homosexual). Homosexual men were 82% more likely to be non-right-handed than heterosexual men, but no significant differences were found between heterosexual and homosexual women in terms of handedness. When combining men and women into one large sample, homosexual individuals were 50% more likely to be non-right-handed than heterosexual individuals.

Blanchard ''et al''., 2006 study

Blanchard ''et al''. argued that the

(the probability that a boy will be homosexual increases with the number of older brothers who have the same biological mother) appears to be limited to right-handed men. Moreover, the same study indicates that left-handed men without older brothers are more likely to be homosexual than non-right-handed men who have older brothers. As Blanchard ''et al''. said in their report, :The odds of homosexuality is higher for men who have a non-right hand preference or who have older brothers, relative to men with neither of these features, but the odds for men with both features are similar to the odds for men with neither.

BBC survey

In a multinational online survey, it was found that

gay men Gay men are male homosexuals. Some bisexual men, bisexual and homoromantic men may dually identify as ''gay'' and a number of gay men also identify as ''queer''. Historic terminology for gay men has included ''Sexual inversion (sexology), in ...

and lesbians are more likely to be left-handed (13 and 11%, respectively) than heterosexual men and women (11% and 10%, respectively). Bisexuals of both sexes more often described themselves as ambidextrous than gay or heterosexual individuals of the same sex (bisexual men: 12%; gay and heterosexual men: 8%; bisexual women: 16%; lesbians: 12%; heterosexual women: 8%).

Blanchard, 2008 ''Archives of Sexual Behavior'' study

A subsequent study by Blanchard found that both right-handed homosexual men and left-handed heterosexual men had a statistically significant number of older male siblings, but that there was no significant observable effect either for right-handed heterosexual men or for left-handed homosexual men.

Blanchard, 2008 ''Laterality'' study

Blanchard discussed ways in which the

and handedness could be explained in terms of the maternal immune hypothesis. In this, the mother is assumed to grow more immune to male

antigens In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. An ...

with each pregnancy, and thus produce a greater number of "anti-male"

antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...

. He suggests two possibilities: Either that non-right-handed fetuses are less sensitive to the antibodies, or that the mothers of left-handed fetuses do not, for some reason, produce them.

Schwartz ''et al''., 2010 hair whorl study

In a sample including 694 gay men and 894 straight men, it was found that 13.9% of gay men and 15.9% of straight men were not right-handed, a non-significant difference. The study replicated the 'older brother effect' for homosexual men, but unlike Blanchard (2006) (see above), it found that the effect applied to both right-handed and left-handed gay men, being in effect stronger for the latter than for the former.

Kishida and Rahman, 2015

In a sample of 478 heterosexual men and 425 homosexual men, gay men were found to show a significantly greater likelihood of extreme right-handedness and non-right-handedness compared to heterosexual men.

Lee Ellis ''et al''., 2016

Among a sample of university students in

Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...

and the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, it was found that same-sex attraction was linked with left-handedness among women. Among men, no such correlation was found after controlling for ethnicity.

Asexuality

A 2014 Internet study attempted to analyze the relationship between self-identification as

asexual Asexual or Asexuals may refer to: *Asexual reproduction **Asexual reproduction in starfish *Asexuality, the lack of sexual attraction to anyone or lack of interest in or desire for sexual activity. **Gray asexuality, the spectrum between asexualit ...

, handedness and other biological markers, in comparison to individuals of other sexual orientation groups. A total of 325 asexuals (60 men and 265 women), 690 heterosexuals (190 men and 500 women), and 268 non-heterosexuals (64 men and 204 women) completed online questionnaires. The study asserts that asexual men and women were 2.4 and 2.5 times, respectively, more likely to not be right-handed than their heterosexual counterparts.

References

{{Laterality Motor skills Sexual orientation and medicine Sexual orientation and science Handedness