No woman has yet won one of the three top mathematics awards–the Fields, the Abel, or the Wolf. It’s part of what’s often called the math gender gap, which in the United States starts early—at least twice as many boys as girls score in the 99th percentile on state-level math assessment tests.

Five years ago, then Harvard president Lawrence Summers’s suggestion that women lack an ”intrinsic aptitude” for math and science drew a firestorm of protest, but he was drawing on a century-old hypothesis that males exhibit greater variability in many features, math included. By such reasoning, it is possible for girls to be as good as boys in math on average but to be less well represented in the upper (and lower) echelons.

This, Summers said, is one reason there are fewer women in tenured science and engineering positions at top universities and research institutions. ”I would like nothing better than to be proved wrong,” he added.

A recent study published in the *Proceedings of the National Academy of Sciences* might make him happy. In it, psychologists Janet Hyde and Janet Mertz, from the University of Wisconsin–Madison, used data from math aptitude tests to show that among top math performers, the gender gap doesn’t exist in some ethnic groups and in some countries. The researchers conclude that culture is the main reason more men excel at the highest math levels in most countries.

”When parents are asked to estimate their child’s math talent, they estimate higher numbers for their sons than their daughters despite similar grades in school,” Hyde says. Teachers and guidance counselors share this bias, which is why math has served as a filter to keep young women out of science, technology, and engineering.

In some circles, the finding came as no surprise. ”Female mathematicians always knew that there were no gender differences, especially since there’s no difference in other countries,” says Bhama Srinivasan, a math professor at the University of Illinois at Chicago, where 40 percent of undergraduate math majors are women. ”My women colleagues have remarked why there should be so many studies. People raise this issue over and over rather than being satisfied.”

But what of the statistics that seem to back up the hypothesis that males have greater variability? Hyde and Mertz found there are more girls in the top tier in countries such as Iceland, Thailand, and the United Kingdom–and even in certain U.S. populations, such as Asian-Americans. Furthermore, they noted that a small math gender gap correlated with a higher rank on the World Economic Forum’s 2007 measures of gender equality, in which the United States ranked 31st, between Estonia and Kazakhstan. A similar correlation was found for the number of girls on International Mathematical Olympiad teams.

So how does culture shape how women do in math? Hyde says that in many countries, especially those in Asia, excellence at math is considered a result of hard work. By contrast, in the United States it is more commonly believed that people are born with or without a gift for math, a subject that in any case is thought to be hard, and not only for girls. Then there’s the cultural perception of math achievers–the nerds who are heckled in one society are exalted in another. Irina Mitrea, a math professor at Worcester Polytechnic Institute, in Massachusetts, who finished high school in Romania, says she never felt discouraged there: ”In fact, being good at math made you popular.” Romania’s International Math Olympiad team has had one of the highest ratios of females of all top-ranked teams in the past decade.

Hyde believes that the gender gap among top math achievers will continue to narrow. In the United States, more and more girls now take advanced math in high school, and they perform on par with the boys. In a 1990 study, Hyde had found that high school boys solved complex problems on standardized tests better than girls. But 19 years later, test scores of 7 million students across 10 states show that the gap is close to zero.

## To Probe Further

For more on the progress of women in math and engineering, see "Math and Gender."

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