I have to imagine that everyone’s heard of the various studies and reports that claim that men tend to have longer ring fingers than index fingers, then go on to link any number of other traits and factors–athletic ability, sexuality, spatial reasoning, stock market success, autism–to digit length ratio. The Wikipedia page has some relatively plausible information about why the correlation might exist–at least between gender and digit ratio–but also notes that there’s a large overlap in the ratio distributions between genders.

Frankly, there’s not much in modern pop culture notions of science that sets my bullshit detector ringing quite like this stuff. It stinks of phrenology and palmistry, though I haven’t yet found anyone claiming a causal link between digit ratio and any of these other things (except that supposedly the ratio is evidence of prenatal exposure levels to masculinizing hormones). And despite this, I haven’t been able to find much of anything–support or skepticism–in the usual skeptical sources. There are a couple of threads on the JREF forums that bat it around a little, but no one seems to have anything solid one way or another on the subject. The one thing that seems to pop up every time I find this topic is a chorus of comments from people for whom the supposed correlation fails; anecdotal, uncontrolled, and self-selected though such a population is, it does suggest to me that the correlation might be less strong than the popular understanding suggests.

So I put the question to you, dear readers: Know of any solid research definitively supporting or debunking the digit ratio connection stuff? In addition, what do you think about it?


2 Responses to Finglonger?

  1. Call me Paul says:

    I have an experiment for you to try. Look at the backs of your hands. Is your ring finger longer than your index finger? Now, look at the palms of your hands. Which finger is longer now?

  2. Doubting Tom says:

    Dude, that's like, totally crazy. Granted, my ring finger didn't necessarily look shorter than my index finger each time I did that, but the difference looked to be a lot less significant. I knew I could vary the apparent ratio by changing how I held my hand, but didn't realize that supination had such a profound effect on its own. This really seems to invalidate a great deal of the lay-tests–people looking at their finger ratios after reading an article, for instance–but makes me wonder if there's a more reliable way that the doctors use to measure the ratio. Could they be taking X-Rays and measuring the actual length of the phalanges? In that case, I wonder if they're controlling for differences in the metacarpals and cartilage thickness and whatnot. Then again, X-Rays are inherently 2-dimensional, which means there could be perspective issues depending on how the hand is placed on the slide; I suppose the best option would be an MRI or something then. Looks like I better take a look at some of the PubMed abstracts.

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