Finally, the opt-out articles never acknowledge the widespread hostility toward working mothers. Researching the book I wrote for Evelyn Murphy in 2005, Getting Even: Why Women Don’t Get Paid Like Men—and What to Do About It, I was startled by how many lawsuits were won because managers openly and publicly told women that they couldn’t be hired because they were pregnant; or that having a child would hurt them; or that it was simply impossible for women to both work and raise kids. Many other women we talked with had the same experience, but chose not to ruin their lives by suing. One lawyer who’d been on the partner track told us that once she had her second child, her colleagues refused to give her work in her highly remunerative specialty, saying that she now had other priorities—even though she kept meeting her deadlines, albeit after the kids were asleep. She was denied partnership. A high-tech project manager told me that when she was pregnant in 2002, she was asked: Do you feel stupider? Her colleague wasn’t being mean; he genuinely wanted to know if pregnancy’s hormones had dumbed her down. Or consider the experience of Dr. Diane Fingold, an internist at Massachusetts General Hospital in Boston and an assistant professor at Harvard Medical School, where she won the 2002 Faculty Prize for Excellence in Teaching, the school’s highest teaching award. Her credentials are outstanding, yet when she asked to work three-and-a-half fewer hours a week so that she could manage her family demands—“just a little flexibility for a short period in my life!”—her practice refused. She was enraged. “I thought hard about leaving medicine altogether,” she said. Her husband is a successful venture capitalist whose “annual Christmas bonus is what I make in a year!”

Had Fingold left, in other words, she would have fit neatly with Belkin’s hyperachievers. But she loves practicing and teaching medicine, and realized she couldn’t reenter at the same level if she walked away entirely. So she moved to another practice that was willing to accommodate her part-time schedule until, in a few years, she can return to full-time. Had she chosen the Belkin course, would she have opted out—or been pushed out?

Experiences like Fingold’s bear out what social scientists are finding: strong bias against mothers, especially white mothers, who work. (Recent research shows bias against African American mothers of any class who don’t work, a subject that deserves an article of its own.) Consider the work being done by Shelley Correll, a Cornell sociology professor, described in an article in the March 2007 American Journal of Sociology. In one experiment, Correll and her colleagues asked participants to rate a management consultant. Everyone got a profile of an equally qualified consultant—except that the consultant was variously described as a woman with children, a woman without children, a man with children, and a man without children. When the consultant was a “mother,” she was rated as less competent, less committed, less suitable for hiring, promotion, or training, and was offered a lower starting salary than the other three.

Here’s what feminism hasn’t yet changed: the American idea of mothering is left over from the 1950s, that odd moment in history when America’s unrivaled economic power enabled a single breadwinner to support an entire family. Fifty years later we still have the idea that a mother, and not a father, should be available to her child at every moment. But if being a mom is a 24-hour-a-day job, and being a worker requires a similar commitment, then the two roles are mutually exclusive. A lawyer might be able to juggle the demands of many complex cases in various stages of research and negotiation, or a grocery manager might be able to juggle dozens of delivery deadlines and worker schedules—but should she have even a fleeting thought about a pediatrics appointment, she’s treated as if her on-the-job reliability will evaporate. No one can escape that cultural idea, reinforced as it is by old sitcoms, movies, jokes—and by the moms-go-home storyline.

Still, if they were pushed out, why would smart, professional women insist that they chose to stay home? Because that’s the most emotionally healthy course: wanting what you’ve got. “That’s really one of the agreed-upon principles of human nature. People want their attitudes and behavior to be in sync,” said Amy Cuddy, an assistant professor in the management and organizations department at Northwestern Kellogg School of Management. “People who’ve left promising careers to stay home with their kids aren’t going to say, ‘I was forced out. I really want to be there.’ It gives people a sense of control that they may not actually have.”

E.J. Graff is senior researcher at Brandeis University’s Schuster Institute for Investigative Journalism