A British study suggests that sexual orientation in women may be influenced by the level of prenatal exposure to testosterone. Explanations.
What is the relationship between finger length and sexual orientation? Put like this, the question seems crazy. Researchers in psychology from the University of Essex (United Kingdom) have just shown the probable existence of such a link. their work, appeared in Archives of Sexual Behavior, suggest that women’s sexual orientation could be partly a matter of… testosterone.
The key to the mystery lies in Manning’s index. Defined as the length ratio between the index and ring fingers, this ratio is considered a marker of prenatal exposure to male hormones. The more a fetus is exposed to testosterone during the first weeks of its development, the more it tends to have a low Manning index (index shorter than the ring finger). To put it simply, we speak of a “masculinized” (low) or “feminized” (high) index.
Show your fingers
In this study, researchers looked at the sexual orientation of twins. More specifically, the psychologists selected twins – 14 pairs of men and 18 of women – one of whom was heterosexual and the other was not. The underlying hypothesis was the following: if prenatal exposure to androgens plays a role in sexual orientation in adulthood, the Manning index must differ within siblings.
And that’s what the measurements have shown, at least in women. As a trend, the 18 heterosexual twins in the experiment had a more “feminized” Manning index than their homosexual (15 of them) or bisexual (the other 3) sisters. A slight difference, to the point that it was significant… only for the left hand. In men, nothing of the sort has been demonstrated.
Not much choice
Taken in isolation, this type of study on very small numbers is not of great value. But it corroborates the results of previous similar research on sexual orientation, including in twins (Hall & Love, 2003).
“Research suggests that our sexuality is determined in utero and depends on how much androgen our bodies are exposed to or how our bodies respond to these hormones,” valued psychologist Tuesday Watts, who conducted the experiment. “Individuals exposed to higher levels of testosterone are more likely to be homosexual or bisexual.”
A final remark: the effects measured on the Manning index express statistical differences of small magnitude. No need to stare at anyone’s fingers to try to read their preferences: it would be doomed to failure!
.
