A few years ago, Harvard President Larry Summers drew a firestorm of criticism for suggesting that the gender gap in science might be a result of innate differences in males and females.

Stephen Pinker defended the basic idea here, using differences in variability as part of the argument:

And biologists since Darwin have noted that for many traits and many species, males are the more variable gender. So even in cases where the mean for women and the mean for men are the same, the fact that men are more variable implies that the proportion of men would be higher at one tail, and also higher at the other. As it's sometimes summarized: more prodigies, more idiots.

Here's the relevant slide from Pinker's presentation:



If the green line represents the distribution of values in female traits and the purple line represents those of males, you can see graphically what Pinker is talking about (although in the text he talks about the means being the same, but you can see the same effect even if the mean of females is higher).

So is this a real phenomenon? Does it help explain the gender gap in science? Or is it junk science, propped up by people with an agenda?

I don't know. It's a reasonable-sounding explanation, but that doesn't make it true. First of all, I could buy that the distribution of male traits tends to be more variable that that of females. But that doesn't mean that for any given individual trait or subset of traits the same thing is true. For example, males could have larger variance in height than females, but no difference in variance in eye color. And cognitive traits are much more difficult to objectively measure than biometrics.

The only way to definitively answer questions like these would be to raise populations of males and females under exactly the same conditions, controlling for everything else but gender. And that's impossible.

There's no doubt that there have been institutional impediments to women advancing in science. Rather than trying to find dubious post hoc explanations, work should be done to make sure that bias and discrimination are mitigated as much as possible and just let the ratio of males to females fall out where it may.