What your fingers might say about what a jerk you are

Ah, the old 2D:4D Ratio. It is the relationship between the length of your second and fourth fingers, respectively. Current embryological theory holds that the amount of testosterone a baby is exposed to in its final trimester of gestation determines the amount of testosterone the resulting baby will have. As a side effect of this same exposure, the ring finger also grows slightly. Because of this, the difference in length between the second and fourth fingers suggests a person’s relative testosterone levels.

As you might imagine, the notion that finger length might indicate virility has been a popular subject in the media and your average drunken conversation at Mark’s Texas Hots ever since it was first announced. And all manner of male traits have been, rightly or wrongly, associated with this ratio in news articles.

Now, the University of Buffalo has discovered another possible angle: that verbal aggression like slurs, ridicules and insults, have biological origins that can be indicated by the whole finger thing. From the article:

… they first measured the finger length of adult subjects from the point where fingers meet the palm to the tip, then photocopied each hand, palm down and made the same measurements. From these results they calculated each subject’s 2D:4D ratio.

The subjects then filled out the Verbal Aggression Scale and the HEXACO Personality Inventory and the Argumentativeness Scale.

The team found that men and women with smaller 2D:4D ratio reported themselves to be more verbally aggressive.

In other words, the closer the second and fourth fingers were in length, the more verbal aggressiveness was reported by the subject.

The study seems to be dancing around a much more verifiable and quantifiable theory: that higher testosterone levels lead to more aggressive speech habits. Would it not have been more efficient to test this theory? This study seems to run the risk of trying to make two causal jumps in a single correlation.

That is: first, that testosterone and finger size are related. And second, that verbal aggressiveness and testosterone are related. To leapfrog between the two seems a bit sloppy.