Last year, researchers in the U.K. studied 2,000 people's hands, hips, knees and risk factors for arthritis. All things being equal, they found a person with a low digit ratio is more likely to develop osteoarthritis of the knee.
Scientists have even started to use the digit ratio to study student aptitude.
In 2007, U.K. researchers found a link between 7-year-olds' standardized test scores and their digit ratios; the lower the digit ratio, the higher the math scores.
But, digit ratios are not that clear cut. Plenty of women have the stereotypically male digit ratios, and plenty of men have the stereotypically female ratios. Moreover, digit ratio can vary by ancestry.
That difference has some researchers skeptical of every digit ratio study to hit the news.
"It's easy to administer some questionnaires and measure finger length -- the literature is probably full of those," said David Andrew Puts, an assistant professor in the department of anthropology at Penn State University in University Park, Pa.
"I think that it's a really intriguing marker but I tend to be really skeptical of these results until I see it replicated by a bunch of different studies," he said.
Puts has published studies using digit ratios and says he may use them in the future. However, he's followed up on many of the so-called digit ratio traits. For example, Puts reviewed studies of spatial relation skills. While one study found better spatial relation skills with a low digit ratio, comparing the findings of many other studies did not.
The connection "was essentially zero," said Puts.
Simon LeVay, a former neuroscientist who researches the brain and sexuality, has a similar reaction to digit length studies.
"It's a serious field of study," said LeVay, noting there is evidence linking exposure to testosterone to finger length.
But LeVay cautions against personal digit reading for various traits. Across hundreds or thousands of people, a reliable statistic correlation may be found.
"It's a kind of weak label, if you'd like," he said. "You can't say anything about any one individual by looking at finger length ratios."
The AP contributed to this report.
Do you have more information about this topic? If so, please click here to contact the editors of ABC News.
