In one study, Martha Carr, a professor of educational psychology at the University of Georgia, looked at first graders who were learning to add and subtract using “manipulatives,” like counting with their fingers or with beads. Midway through the year, she noticed that most boys were abandoning the manipulatives and were doing the problems in their heads by recalling the answers from memory. Most girls, meanwhile, continued to use the manipulatives.

At first glance, such a result might suggest that boys have a natural advantage in arithmetic. But the difference had nothing to do with ability, Ms. Carr says. “Basically,” she explains, “a lot of the boys were guessing.”

The boys had stopped using the manipulatives because it took too much time, and the boys were vying to answer first. “There’s this competitive one-upmanship, and that supports the move toward retrieval,” she says. By the end of the year, boys and girls were doing the problems equally well, but boys could answer the problems from memory, while girls were still using the technique they had been taught.

In general, girls tend to follow instructions better than boys do, which made the girls less likely to change strategies on their own, says Ms. Carr. So it was the boys’ competitive nature — whether learned or innate — that caused them to make leaps in learning. —Rich Monastersky —Women and Science: The Debate Goes On: Primed for Numbers (Chronicle)

This is a complex subject. Here’s an excerpt describing a different study:

The researchers found that, in general, mathematically gifted females had broader abilities than did mathematically talented males. Girls tended to show more balance between their math and verbal SAT scores, while boys had more of a tilt, scoring higher on the math section and lower on the verbal.

That “quantitative tilt” turned out to be an important factor, the researchers said. Students with exceptional math abilities were less likely to major in math or science if they also had high verbal skills.