Decades' worth of social-psychology research has demonstrated that humans classify each other by race and gender and respond instinctively based on stereotype and social norms. In the workplace, these unconscious biases mean white men are more likely to be hired, promoted, and paid well compared with equally deserving women or racial minorities.
One famous experiment found that resumes that appeared to be from white people received 50 percent more interviews than identically qualified applications from black candidates. This effect shows up even when the decision maker is from the less-powerful group. A more recent study showed that men and women alike were twice as likely to hire a man for a math-intensive job, even when the candidates’ math skills were identical. Awareness of implicit bias has grown thanks to academic initiatives such as Project Implicit and grassroots blogs like the Microaggressions Project and I, Too, Am Harvard, which is now a YouTube meme, as well as media coverage and advocacy by business leaders such as Facebook's Sheryl Sandberg.
A key difference between this sort of unconscious bias and more deliberate discrimination is that those perpetuating it often wish they could stop it, if only they knew how. Existing efforts—such as diversity training programs and exhorting women to "lean in"—may actually backfire; for example, women who negotiate for raises may do themselves more harm than good. “There are all kinds of really well-meaning people in corporate America who are sincerely distressed that they have spent many millions of dollars trying to retain and advance women and minorities and it ain’t working. They are baffled about what to do,” says Joan C. Williams, a law professor at the University of California, Hastings.