Sometimes it is difficult to decide who to be more irritated at … the researchers who publish highly dubious data, the PR people who send out the breathless press releases touting the highly dubious data, or the media that actually publish these data as if they are correct and/or important.
For many years people have published data suggesting that the relative lengths of people’s fingers may be associated with risk for specific medical conditions or may be used as indicators of specific capabilities. Here’s a relatively recent one that probably wouldn’t convince you that one particular hedge fund manager would be a better overseer of your investments (if you actually have any) than another with a different finger length ratio.
And here’s one from The Daily Mail today suggesting that men with a relatively long ring finger compared to their second finger (and only on the right had at that) are at three times greater risk for prostate cancer than other men. (It includes a photograph of the late Dennis Hopper, but no photograph of his hands to help us know whether his ring finger was longer than his second finger.)
Nearly all of these articles are based on the premise that the levels of androgens to which babies are exposed in their mothers wombs have an impact on the comparative lengths of the second and the fourth fingers of the right and the left hands. However, a recent article by Berenbaum et al. clearly indicates that there is little to no data to support this hypothesis at all. Even the article on digit ratios on Wikipedia , which spends a good deal of time trying to justify the “androgens in utero” hypothesis, starts out by stating clearly:
It has been suggested by some scientists that the ratio of two digits in particular, the 2nd (index finger) and 4th (ring finger), is affected by exposure to androgens, e.g., testosterone, while in the uterus and that this 2D:4D ratio can be considered a crude measure for prenatal androgen exposure, with lower 2D:4D ratios pointing to higher androgen exposure.
There is no suggestion in the article that this association has been clearly proven let alone that there are extended implications from this unproven hypothesis such as a correlative impact of prenatal androgen exposure to risk for prostate cancer. The hypothesis has simply been “suggested” by “some scientists.”
There is a term for this type of argument in the discussion of logic. It is called a syllogism, in which a conclusion is drawn from two propositions of a particular form. Here is a famous example of a syllogism, propounded by the philosopher Socrates some time before 400 BC:
Major premise: All men are mortal.
Minor premise: Socrates is a man.
Conclusion: Socrates is mortal.
And here is another:
Major premise: Men are exposed to higher levels of androgens in utero than women.
Minor premise: Men have longer ring fingers than second fingers.
Conclusion: Higher levels of androgens in utero cause men to have longer ring fingers than second fingers.
The first syllogism is absolutely true, and there is independent evidence to support each of the three statements. The second syllogism is just a syllogism. We have no evidence that actually substantiates the first premise, the second premise, or the conclusion at all.
The article on syllogisms on Wikipedia gives numerous examples of “false syllogisms” through which it is made clear that even two logical and demonstrable premises do not necessarily lead to the proposed conclusion. We suggest that (at least for the majority of men) the premise that the relative lengths of their second and fourth fingers is not necessarily associated with prostate cancer at all. We are pleased to note that the head of health information for Cancer Research UK appears to be in complete agreement with us.