*New data about the science aptitude of boys and girls around the world inspires me to re-post this discussion from 2010.*

Math ability, in some societies, is gendered. That is, many people believe that boys and men are better at math than girls and women and, further, that this difference is biological (hormonal, neurological, or somehow encoded on the Y chromosome).

But actual data about gender differences in math ability tell a very different story. Natalie Angier and Kenneth Chang reviewed these differences in the *New York Times*. They report the following (based on the US unless otherwise noted):

• There is no difference in math aptitude before age 7. Starting in adolescence, some differences appear (boys score approximately 30-35 points higher than girls on the math portion of the SAT). But, scores on different subcategories of math vary tremendously (often with girls outperforming boys consistently).

• When boys do better, they are usually also doing worse. Boys are also more likely than girls to get nearly all the answers wrong. So they overpopulate both tails of the bell curve; boys are both better, and worse, than girls at math.

• That means that how we test for math ability is a political choice. If you report who is best at math, the answer is boys. If you report average math ability, it’s about the same.

• How you decide to test math ability is also political. Even though boys outperform girls on the SAT, it turns out those scores do not predict math performance in classes. Girls frequently outperform boys in the classroom.

• And, since girls often outperform boys in a practical setting, math aptitude (even measured at the levels of outstanding instead of average performance) doesn’t explain sex disparities in science careers (most of which, incidentally, only require you to be pretty good at math, as opposed to wildly genius at it). In any case, scoring high in math is only loosely related to who opts for a scientific career, especially for girls. Many high scoring girls don’t go into science, and many poor scoring boys do.

Now, let’s look at some international comparisons:

• Boys do better in only about ½ of the OECD nations. For nearly all the other countries, there were no significant sex differences. In Iceland, girls outshine boys significantly.

• In Japan, though girls perform less well than the boys, they generally outperform U.S. boys considerably. So finding that boys outperform girls within a country does not mean that boys outperform girls across all countries.

• Still, even in Iceland, girls overwhelmingly express more negative attitudes towards math.

So what’s the real story here? Well, one study found that the gender gap in math ability and the level of gender inequality in a society were highly correlated. That is, “…the gender gap in math, although it historically favors boys, disappears in more gender-equal societies.”

Part of the problem, then, is simply that girls and boys internalize the idea that they will be bad and good at math respectively because of crap like the “Math class is tough!” Barbie (sold and then retracted in 1992):

However, girls’ insecurity regarding their own math ability isn’t just because *they* internalize cultural norm, their elementary school teachers, who are over 90% female, sometimes do to and they teach math anxiety by example. A recent study has shown that, when they do, girl students do worse at math. From the abstract (this is pretty amazing):

There was no relation between a teacher’s [level of] math anxiety and her students’ math achievement at the beginning of the school year. By the school year’s end, however, the more anxious teachers were about math, the more likely girls (but not boys) were to endorse the commonly held stereotype that “boys are good at math, and girls are good at reading” and the lower these girls’ math achievement. Indeed, by the end of the school year, girls who endorsed this stereotype had significantly worse math achievement than girls who did not and than boys overall.

So, with only the possible exception of genius-level math talent, men and women likely have equal potential to be good (or bad) at math. But, in societies in which women are told that they shouldn’t or can’t do math, they don’t. And, as Fatistician said, “math is a skill.” People who think practicing it is pointless won’t practice it. And those who don’t practice, won’t be any good at it… Y chromosome or no.

*Lisa Wade is a professor at Occidental College and the co-author of Gender: Ideas, Interactions, Institutions. Find her on Twitter, Facebook, and Instagram.*