“Let’s call the whole thing off,” the George and Ira Gershwin song once suggested. But if pop music lyrics and romantic comedies weren’t enough, new scientific evidence is confirming what some bickering couples have known all along: there are significant, and at times frustrating, contrasts in the ways that male and female brains operate.

Scientists still argue about just what defines gender brain differences, Natalie Angier and Kenneth Chang pointed out in The Times. But they have moved beyond the theory of Gustav le Bon, who posited a century ago that the smaller size of women’s brains explained their “fickleness, inconstancy, absence of thought and logic, and incapacity to reason.”

Today, brain imaging studies suggest that men and women use different parts of their brains to solve problems. While men turn to gray matter, women rely more heavily on white matter. And the corpus callosum, which connects the brain’s right and left hemispheres, is thought to be 25 percent larger in women. One writer, Shaunti Feldhahn, believes that such differences facilitate multitasking in women and compartmentalization in men .

As for hormones, in her book “The Male Brain,” Louann Brizendine cites the deep influence of testosterone, androstenedione and vasopressin on the perceptions and behavior of men, especially in regard to risk taking and sex.

“The female brain wants the hope of love and commitment before having sex,” Ms. Brizendine writes, “but for men, sex often comes first.”

To which Holly Brubach, writing about the book in The Times, responded: “News bulletin: Scientists Discover What Any Woman in a Bar Could Have Told Them.”

In the wake of the global financial crisis, the cocktail of hormones coursing through the male brain has been under more scrutiny lately. Studies show that higher levels of testosterone promote excessive risk taking, and some critics cite the exclusive boys club of Wall Street as Exhibit A in what can happen when an all-male culture revels in high-risk gambles. One of those critics, William D. Cohan, writing for The Times’s Opinionator blog, suggested that what Wall Street needed most was an estrogen injection.

While male bastions like Wall Street and Silicon Valley remain difficult for women to enter, girls are surpassing boys in other ways. Nicholas D. Kristof explored in The Times why the reading scores of boys lag behind girls in many countries. “Many theories have been proposed,” he wrote, adding that “some people think boys are hard-wired so that they learn more slowly, perhaps because they evolved to fight off wolves more than to raise their hands in classrooms.”

But as men age into the period of life known as andropause, testosterone and vasopressin decline, and estrogen has more influence on behavior. As Ms. Brizendine wrote in The Times: “Hormonally, the mature male brain is becoming more like the female.”


KEVIN DELANEY