By Sally Raskoff

Do you think you can tell a person’s sexual orientation just by looking at them? A recent New York Magazine article by David France suggests that there are physical characteristics that indicate one’s sexual orientation as straight, gay or lesbian. Lately, research has focused on such markers as a person’s finger length, fingerprint density, the direction that hair swirls on one’s head, and left or right handedness.

According the researchers France cites, finger length, or, more specifically, the ratio of the second digit (index or pointer finger) to the fourth digit (ring finger), can indicate sexual orientation for both men and women, although in opposite patterns. Men with a smaller ratio (index fingers are shorter than their ring fingers) would indicate a heterosexual orientation while men with a larger ratio (index fingers longer than their ring fingers) would indicate a homosexual orientation. Alternatively, women with a larger ratio, those deemed heterosexual, would have longer index fingers and women with a smaller ratio (index finger shorter than their ring finger) would be lesbian.

Did you stop reading here to look at your fingers or your hair? I did when I first heard the story on NPR’s Talk of the Nation.

The article has received a lot of media attention (including from Comedy Central’s The Colbert Report) which seemed to assume that these patterns are real and reliable. Thus the public who hears about this research might assume that one can identify people’s sexual orientation by their relative finger lengths and hair swirls.

As a sociologist, this news story has me wondering what the researchers actually said and, if indeed these are valid and reliable findings, how strong are these supposed patterns?

Looking up related peer-reviewed research on my campus library’s webpage, I found many articles relating to these issues. Many of them do find statistically significant differences in these characteristics between those who identify as heterosexual, gay, or lesbian; but it took me a while to find the details on the strength of these patterns. But depending on the characteristic in question, the significance of these patterns is not overwhelming.

Let’s start with handedness. A study published in 2003 by Richard Lippa found that homosexual men have an 82% greater chance than heterosexual men of being non-right handed (left handed or ambidextrous). This is a statistically significant difference based on his research finding that 11.4% of heterosexual men and 19.0% of homosexual men are non-right-handed. His findings for  women were not significant.

Regarding the finger length issue, studies have found differences depending on gender, ethnicity, and which hand one is looking at. A comprehensive analysis of this research published in 2005 highlights that in the five studies they analyzed, there is more variation in the finger length ratio among heterosexual people than there is among homosexual people.

Many of these studies are done to assess whether genetics or in-utero conditions have a greater effect on human development. Another study of finger length used a sample of identical twins (who of course have identical genes) to assess the role of genetics versus the “prenatal environment.” The researchers tested seven twin pairs who were “discordant” for sexual orientation (one twin was heterosexual and the other homosexual in orientation), and five twin pairs who have “concordant” (the same) sexual orientation. Their findings did indicate a statistically significant difference in ratios for both the left and right hands, with the heterosexual twins having greater ratios between their second and fourth fingers than their homosexual twins.

If you look closely at the twin data, however, you’ll see that the differences in ratios are not overwhelming. In the analysis of data from five previous studies, the ratios for each gender group were also not overwhelmingly different across sexual orientation groups.

All in all, my journey into the actual research did show that there are some interesting physical differences across groups. However, those patterns can easily be misinterpreted and applied in inappropriate ways. Just because the researchers found statistically significant differences does not mean that having a particular finger ratio indicates homosexuality. For example, in the handedness study, while gay men may have a higher chance of being non-right-handed compared to straight men, it does not follow that left-handed men are gay– keep in mind that less than 20% of men in either group are non-right handed!

Studies on finger length ratios and the other characteristics alleged to be associated with sexual orientation are vulnerable to the same kind of interpretation error. If you look at your index and ring fingers and assess which is longer, does this indicate your sexual orientation? Some people might question their sexual orientation once they hear of this research and identify their own finger ratio. However, this is a misuse of this research and a misinterpretation of the data. While many straight men and lesbian women may have shorter index fingers relative to ring fingers, there will be plenty of straight men and lesbian women who have comparatively longer index fingers. Likewise, there are many gay men and straight women with same length or longer index fingers, there are also gay men and straight women with shorter index fingers.

When I see news items that mention relationships like these, I know that it’s a good idea to see what the researchers actually said and if the public hears the same story. The media’s job of translating the scientific world for the public is a difficult task and is sometimes impossible considering the lack of scientific expertise of most reporters, restrictions on time, the need to avoid scientific language, and the wish to have the simplest explanation of very complex phenomena. Since the media is often more concerned with generating the most sensational headline than it is with relaying information accurately, it is imperative that we educate ourselves to assess research studies ourselves and to identify the most accurate information in them.

Having established that there are statistically significant patterns in finger length, does this mean that homosexuality creates different finger lengths? Or that finger length ratios create homosexuality? Remember, these studies cannot support a strong causal relationship between these characteristics and homosexual orientation because of the high levels of variation within groups. This brings to mind an important phrase you may have heard in sociology or other classes: correlation is not causation.