Girls can do just as well at math as boys -- even at the genius level -- if they are given the same opportunities and encouragement, researchers reported.
Their study, published in the Proceedings of the National Academy of Sciences, contradicts studies showing girls can do as well as boys on average in math -- but cannot excel in the way males can.
They also said it is a clear rebuttal to Larry Summers, who as president of Harvard University said in 2005 that biological differences could explain why fewer women became professors of mathematics. Summers is now chairman of the Council of Economic Advisers for President Barack Obama.
"We conclude that gender inequality, not lack of innate ability or 'intrinsic aptitude', is the primary reason fewer females than males are identified as excelling in mathematics performance in most countries, including the United States," Janet Hyde and Janet Mertz of the University of Wisconsin in Madison wrote in their report.
They did a statistical analysis comparing various math scores and contests with the World Economic Forum's 2007 Gender Gap Index. This annual report ranks countries according to employment and economic opportunities, education and political opportunities and medical status.
The United States ranks 31 out of 128 nations on the World Economic Forum index.
"We asked questions about how well females relative to males are doing at the average level, at the high-end level -- 95th percentile or above -- and the profoundly gifted level, the one-in-a-million type level," Mertz said in a telephone interview.
"Countries with greater gender equity are also the ones where the ratio of girls to boys doing well in math is close to equal," she said.
GIFTED AND AVERAGE
She said no one disputes that at the average level, girls perform as well as boys mathematically.
But at the top levels, disparities persist and some experts have said this is do to the "greater male variability" theory -- the idea that males in general are more likely to score both extremely high and extremely poorly on tests than girls are.
Mertz said the analysis shows this is not true. "It's not that everywhere in the world there are fewer girls than boys in the top one percent," she said.
If there were a biological reason for the differences, this would have to hold everywhere, she said. But it does not.
"Analysis of data from 15-year-old students participating in the 2003 Programme for International Student Assessment likewise indicated that as many, if not more girls than boys scored above the 99th percentile in Iceland, Thailand, and the United Kingdom," Mertz and Hyde wrote.
Several different international tests show the same pattern, including the International Math Olympics, Mertz said.
"If girls don't have equal educational opportunities or if they know if they learn the material there won't be jobs available to them, why bother, they seek something else," she said.
This is changing, slowly, in the United States, they pointed out.
"For example, only 14 percent of the US doctoral degrees in the biological sciences went to women in 1970, whereas this figure had risen to 49 percent by 2006," they wrote.
"The percentages in mathematics and statistics were 8 percent in 1970 and 32 percent in 2006."