The Length of Your Fingers Could Indicate Your Sexuality

Stock image of a woman displaying her fingers iStock

The length of your finger could provide clues to your sexuality, according to a study published in the journal Archives of Sexual Behavior.

In women, the index (second) finger and ring (fourth) fingers are typically of similar length, while in men there is usually a greater difference between the two (shorter index fingers and longer ring fingers).

Previous studies have suggested that there may be a link between prenatal hormone levels and differences in finger length, with those exposed to higher levels of the hormone testosterone more likely to have "male-typical hands". In the womb, both males and females are exposed to testosterone.

For their research, a team from the University of Essex in the U.K. examined sets of identical twins (14 male and 18 female) with different sexual orientations.

"We are interested in investigating the factors that contribute to such a fundamental difference between these genetically identical individuals," Tuesday Watts, lead author of the study from Essex's Department of Psychology, told Newsweek. "The motivation for this study was to investigate whether differences in the level of exposure to testosterone during early development, was linked to the difference in the twins' sexual orientation."

The researcher observed variations in the hands of their participants. Among the female twins, the bisexual or lesbian sisters were found to have significantly more "male-typical" finger length ratios on average compared to their straight counterparts. Meanwhile, among the male twins, the bisexual or gay brothers had more "male-typical" hands than the straight ones—contrary to what the researchers expected—although the difference was not significant.

"Because identical twins, who share 100 percent of their genes, can differ in their sexual orientations, factors other than genetics must account for the differences," the authors wrote in the study.

For example, different exposure or reactions to "male hormones" (androgens)—such as testosterone—in the womb, unique to each twin pair, could contribute to their differing sexual orientations, particularly for the females.

"Research suggests that our sexuality is determined in the womb and is dependent on the amount of male hormone we are exposed to or the way our individual bodies react to that hormone, with those exposed to higher levels of testosterone being more likely to be bisexual or homosexual," the authors wrote. "Because of the link between hormone levels and difference in finger lengths, looking at someone's hands could provide a clue to their sexuality."

The latest study is not the first to suggest a link between finger length and sexuality. However, it is important to stress, that the evidence is currently not strong enough to accurately predict whether someone is gay, straight or bisexual by looking at the ratio between their fingers.

"This does not allow the identification of someone's sexual orientation by looking at their fingers," Watts said. Importantly, the effects reported in our work and other work only apply in general or on average, rather than to every individual. That is, there are and will be lesbians with "female-typical" ratios. Because of such individual differences, I could not envision ever being able to reliably predict someone's sexual orientation simply by looking at their hands."

"[Furthermore], findings for males are quite inconsistent," she said. "Some work has shown that gay men have more "male-typical" ratios than straight men; other work has shown the opposite pattern; and still further work has shown no difference at all. As such, it is not clear whether there is any real difference in the level of testosterone exposure between straight and gay men or how testosterone exposure might map on to sexual orientation differences."

According to David Puts, a professor in the Department of Anthropology at Pennsylvania State University, who was not involved in the latest research, the study adds to a growing body of evidence indicating that prenatal sex hormones, especially male hormones such as testosterone, play a role in the development of later sexual orientation.

"This is an active area of research, and we're learning more all of the time, but data are increasingly showing that hormones are likely to play a major role in the development of sexual orientation," he told Newsweek.

"In particular, the very large sex difference in prenatal male hormones appears likely to be responsible for the sex difference in sexual orientation (most biological females are attracted to males, and most biological males are attracted to females).

"Male fetuses develop testes, and female fetuses develop ovaries. Testes produce much higher levels of androgens, and like all hormones, androgens travel throughout the body in the bloodstream to influence the development of diverse parts of the body, including the brain," said Puts.

"Biological females and males with endocrine disorders in which prenatal androgen action is affected—for example, biological females whose bodies produced elevated prenatal androgen levels—are also more likely to have non-heterosexual sexual orientations," said Puts.

While the large differences between the sexes in prenatal exposure to male hormone may explain why most biological females are attracted to males and most biological males are attracted to females, smaller variations in prenatal androgen action may account for variation within the sexes, Puts explained. For example, the present study suggests that, within women, elevated androgens increase the likelihood of non-heterosexual orientation.

"[However], the present results also suggest that higher-than-average male androgen levels may increase the likelihood of non-heterosexual orientation in men as well, when taken together with prior research, this interpretation is less certain," Puts said.

"This is not only because previous studies find very mixed associations between male sexual orientation and digit ratios, but also because other biomarkers of early androgen signalling have been unrelated or even related in the opposite direction," Puts said.

This article has been updated to include additional comments from David Puts.

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