“I would like nothing better than to be proved wrong,” Dr. Summers told the economists, expressing the hope that gender imbalances could be rectified simply by eliminating social barriers. But he added, “My guess is that there are some very deep forces here that are going to be with us for a long time.”

Image Credit... Viktor Koen

Dr. Summers was pilloried for even suggesting the idea, and the critics took up his challenge to refute the hypothesis. Some have claimed he was proved wrong by recent reports of girls closing the gender gap on math scores in the United States and other countries. But even if those reports (which have been disputed) are accurate, they involve closing the gap only for average math scores  not for the extreme scores that Dr. Summers was discussing.

Some scientists and advocates for gender equity have argued that the remaining gender gap in extreme scores is rapidly shrinking and will disappear. It was called “largely an artifact of changeable sociocultural factors” last year by two researchers at the University of Wisconsin, Janet S. Hyde and Janet E. Mertz. They noted evidence of the gap narrowing and concluded, “Thus, there is every reason to believe that it will continue to narrow in the future.”

But some of the evidence for the disappearing gender gap involved standardized tests that aren’t sufficiently difficult to make fine distinctions among the brighter students. These tests, like the annual ones required in American public schools, are limited by what’s called the ceiling effect: If you’re measuring people in a room with a six-foot ceiling, you can’t distinguish among the ones taller than six feet.

Now a team of psychologists at Duke University has looked at the results of tests with more headroom. In an article in a forthcoming issue of the journal Intelligence, they analyze the test scores of students in the United States who took college admissions tests while they were still in the seventh grade. As part of an annual talent search since 1981, the SAT and ACT tests have been given to more than 1.6 million gifted seventh graders, with roughly equal numbers of boys and girls participating.

The Duke researchers  Jonathan Wai, Megan Cacchio, Martha Putallaz and Matthew C. Makel  focused on the extreme right tail of the distribution curve: people ranking in the top 0.01 percent of the general population, which for a seventh grader means scoring above 700 on the SAT math test. In the early 1980s, there were 13 boys for every girl in that group, but by 1991 the gender gap had narrowed to four to one, presumably because of sociocultural factors like encouragement and instruction in math offered to girls.

Since then, however, the math gender gap hasn’t narrowed, despite the continuing programs to encourage girls. The Duke researchers report that there are still four boys for every girl at the extreme right tail of the scores for the SAT math test. The boy-girl ratio has also remained fairly constant, at about three to one, at the right tail of the ACT tests of both math and science reasoning. Among the 19 students who got a perfect score on the ACT science test in the past two decades, 18 were boys.