Dr. Marc Breedlove

I mean, you can't imagine there's a social influence on digital.

And nobody knew about this.

So I wasn't worried that there were some little girls out there that looked at their hand and say, hmm, gee, that looks kind of masculine.

Maybe I should be a lesbian, right?

Because nobody knew this.

You know, every once in a while, to this day on the internet, I'll look at them and there'll be a little ad over there claiming to tell me something about my personality based on digit ratio length.

And it's just like, you know, please.

Yeah, there's nothing to it.

Don't waste your money, gang.

And there's an aspect of this, this fact that the group differences were there, but you can't tell about differences between individuals, that I think is the hardest thing for scientists to communicate to the public.

Psychologists, they like to talk about a way of measuring how big a difference is between two groups.

So this difference in digit ratios between men and women, it's a relatively small difference.

It's like, well, we measure it in terms of how many standard deviations apart are the two means of the populations.

The two averages.

The two averages.

And to give an example of that, everyone knows about the sex difference in human height, right, among adults.

So that's a huge sex difference.

It's one where we're all aware of it, and if nobody had told us it was such a thing, we'd notice it after a while, right?

And that's because those two averages and those two populations are about two standard deviations apart, the standard deviation being a measure of how much variability there is in something.

So that's a huge sex difference.