Just as boys tend to gravitate to toy trucks and girls usually prefer dolls, the gender differences in math performance have more to do with culture than aptitude. That's according to a new review of relevant studies.

Such findings challenge the century-old idea that males are innately more capable than girls in mathematics.

More recently, the gender bias showed up in the 1990s when Mattel introduced a Barbie doll that said, "Math is hard."

And in 2005, Lawrence Summers, then president of Harvard University and current economic adviser to President Barack Obama, brought the debate into the spotlight again.

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While speaking at an event, Summers stated that males are intrinsically smarter than females in science and engineering.

"I have to say that Larry Summers' comments in 2005 inspired me," to complete the current study, said Janet Hyde, a University of Wisconsin-Madison professor of psychology.

**Math around the world**

Hyde and Janet Mertz, a UW-Madison professor of oncology, analyzed studies from around the world on math performance along with gender inequality as measured by the World Economic Forum's Gender Gap Index.

This index measures the gap between men and women in economic opportunity, educational attainment and other socioeconomic factors.

The researchers knew that if guys were born with math on the brain, so to speak, the gender difference in mathematical ability should be somewhat universal. But some countries showed a larger gap than others.

Countries with low gender equality showed a greater gender gap in math.

For example, India and Iran ranked low on gender equality and low on the percent of females scoring high in the International Mathematical Olympiad, a competition for those with exceptional math skills.

**American girls**

In the United States, which scored relatively high for gender equality, girls perform on average as well as boys on standardized math tests.

Girls in the United States are now taking calculus in high school at the same rate as boys, and the percentage of U.S. doctorates in the mathematical sciences awarded to women has climbed to 30 percent in the 21st century, up from 5 percent in the 1950s.

However, more boys than girls are identified at the upper rungs of the mathematically gifted in the United States. The researchers say this gap is narrowing.

Summers suggested that guys inherently show more variability than gals in math ability, resulting in some guys with soaring math skills.

The variability, he pointed out, could account for the greater number of males with award-worthy math skills. (No woman to date has won a Fields Medal, the Nobel Prize of mathematics.)

But the study results, detailed today in the journal Proceedings of the National Academy of Sciences, showed that girls' math scores are just as variable as boys' in some countries and in some ethnic groups in the United States such as Asian Americans.

While many scientists are beginning to recognize boys are not innately math whizzes compared with girls, Hyde said, some people might be surprised at the new findings.

"There's a gender stereotype that boys are better at math than girls are, and stereotypes die very hard," Hyde told LiveScience. "Teachers and parents still believe that boys are better at math than girls are."

The researchers provide several possible cultural factors keeping females from excelling in math, including classroom dynamics in which teachers pay more attention to boys, while even mathematically gifted girls are not nurtured. In addition, stereotypes may drive guidance counselors and others to discourage girls from taking engineering courses.

In some regions, where women role models in math-intensive careers are scarce, the girls themselves may steer clear of such a path.

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