Among the highest paid corporate executives, only 2.5 percent are women. Among the most elite scientists (those who have been elected to the National Academy of Sciences), fully 9 percent are women. Depending on your biases, you can read that as evidence that women are better at science than business, that corporations discriminate against women, or (if you believe that profit-maximizing corporations get everything just right) that the National Academy discriminates against men.
If you have access to the World Wide Web, you'll have no problem finding theories, evidence, counterevidence, and polemics galore on this subject. Here I just want to talk about one bit of evidence regarding one of the many factors that might be in play: Women—especially high-achieving women—choke under pressure.
You can observe a lot of high achievers under pressure at a Grand Slam tennis tournament. Better yet, you can observe them under variable pressure: Things are a lot tenser when the score is 5-5 than when it's 0-0. Professor Daniele Paserman of Hebrew University made good use of this variability at the 2006 French Open, U.S. Open, and Wimbledon tournaments. First, he assigned an "importance" to each point in each match. He did this by assigning probabilities to every way the match might unfold, accounting for players' ratings, the surface they were playing on, and the identity of the server. That allowed him to say things like, "If Roger Federer wins this point, he has a 60 percent chance to win the match; if he loses the point, he has a 55 percent chance." The 5 percent difference measures the point's importance.
It turns out that by at least one measure—the number of unforced errors—men play equally well throughout the match. They make unforced errors on about 30 percent of the most important points, about 30 percent of the least important, and about 30 percent of all those in between. But women show a very different pattern: 34 percent unforced errors on the least important points, steadily rising to almost 40 percent on the most important. That's almost surely too big a difference to be mere coincidence.
What, besides choking, could explain those numbers? Maybe the closest games are usually played late in the match, when players are more fatigued; maybe more of those games involve weak players; maybe more of them occur at the French Open, where the court is harder to play. But professor Paserman tests all these theories, and none stands up to statistical analysis.
Another countertheory: Maybe women play more defensively when the score is tight. If both players just keep lobbing the ball back and forth, there can't be any forced errors, so all errors are recorded as unforced. In support of this theory, professor Paserman observes that women do play more defensively when the score is tight. (He measures defensive play by speed of serve, length of rallies, and so forth.) But, unfortunately for the countertheory, so do men. When the pressure's on, both men and women get more defensive (and by about the same amount)—but only women make more errors.
Meanwhile, another band of researchers (Uri Gneezy, Muriel Niederle, and Aldo Rustichini, of the University of California at San Diego, Stanford, and the University of Minnesota) has been running experiments to see how men and women perform in competitive environments. First they have subjects solve mazes on their own; then they pit the same subjects against each other in maze-solving contests. The result?
Competition—against anyone—improves men's performance.
Competition against women improves women's performance.
But in competition against men, women do no better than when they're working in isolation.
In spirit, that seems opposite to what professor Paserman is telling us. Women in championship tennis tournaments are always pitted against women, so based on the maze research you'd expect heightened performance—and it's a reasonable guess that when the competition gets tougher, performance should get even better.
But of course there's no real contradiction here: It's perfectly possible that same-sex competition in general improves women's performance, while extremely tight competition degrades it. And of course, these are very different populations of women. The subjects in the maze experiments were engineering students at first-class universities, which is to say they were a pretty elite bunch. But that's still a far cry from being a world-class tennis player.
And of course, just as tennis players differ from engineering students, both groups differ from scientists and business executives. So it would be a bit of a stretch to conclude that what happens on the tennis court must happen in the boardroom or the biology lab. But it might be worth looking into.