The idea that girls are innately less good at math than boys just doesn't add up, a new international study shows.
"We tested some recently proposed hypotheses that try to explain a supposed gender gap in math performance and found they were not supported by the data," says Janet Mertz, senior author of the study and a professor of oncology at the University of Wisconsin-Madison.
Instead, say the Wisconsin researchers, differences in math performance are linked to social and cultural factors.
The study looked at data from 86 countries, which the authors used to test the 'greater male variability hypothesis' famously expounded in 2005 by Lawrence Summers, then president of Harvard, as the main reason there were few outstanding women mathematicians.
Summers suggested that males diverge more from the mean at both ends of the spectrum, making them better-represented in the highest-performing sector.
However, the Wisconsin team says that many countries don't show this greater male variation in math achievement - and that in those that do, it's mostly because the boys are performing worse.
"People have looked at international data sets for many years," says Mertz. "What has changed is that many more non-Western countries are now participating in these studies, enabling much better cross-cultural analysis."
Nor does the Wisconsin study support the idea proposed by Steven 'Freakonomics' Levitt that gender inequity doesn't hold girls back in Muslim countries, where most students attend single-sex schools. Levitt suggested, instead, that Muslim culture or single-sex classrooms benefit girls’ ability to learn mathematics.
But by examining the data in detail, the Wisconsin authors noted other factors at work.
"The girls living in some Middle Eastern countries, such as Bahrain and Oman, had, in fact, not scored very well, but their boys had scored even worse, a result found to be unrelated to either Muslim culture or schooling in single-gender classrooms," says professor Jonathan Kane.
He suggests that Bahraini boys may have low average math scores because some attend religious schools whose curricula include little mathematics. Also, some low-performing girls drop out of school, making the tested sample of eighth graders unrepresentative of the whole population.
“For these reasons, we believe it is much more reasonable to attribute differences in math performance primarily to country-specific social factors,” Kane says.
What does seem to make a difference is gender equality.
"We found that boys — as well as girls — tend to do better in math when raised in countries where females have better equality, and that’s new and important," says Kane. "It makes sense that when women are well-educated and earn a good income, the math scores of their children of both genders benefit."
US students ranked only 31st on the 2009 Programme in International Student Assessment, below most Western and East-Asian countries. Single-sex classrooms have been suggested as a solution - but the new study indicates this won't do much good.
Instead, Mertz and Kane recommend increasing the number of math-certified teachers in middle and high schools, cutting the number of children living in poverty and ensuring gender equality.
"This is not a matter of biology: none of our findings suggest that an innate biological difference between the sexes is the primary reason for a gender gap in math performance at any level," says Mertz.
"Rather, these major international studies strongly suggest that the math-gender gap, where it occurs, is due to sociocultural factors that differ among countries, and that these factors can be changed."