http://www.washingtonpost.com/wp-dyn/content/article/2007/07/29/AR2007072900827_pf.html

Excerpt:
“The traditional explanation for the gender differences that Babcock found is that men are simply more aggressive than women, perhaps because of a combination of genetics and upbringing. The solution to gender disparities, this school of thought suggests, is to train women to be more assertive and to ask for more. However, a new set of experiments by Babcock and Hannah Riley Bowles, who studies the psychology of organizations at Harvard’s Kennedy School of Government, offers an entirely different explanation.

Their study, which was coauthored by Carnegie Mellon researcher Lei Lai, found that men and women get very different responses when they initiate negotiations. Although it may well be true that women often hurt themselves by not trying to negotiate, this study found that women’s reluctance was based on an entirely reasonable and accurate view of how they were likely to be treated if they did. Both men and women were more likely to subtly penalize women who asked for more — the perception was that women who asked for more were “less nice”.

“What we found across all the studies is men were always less willing to work with a woman who had attempted to negotiate than with a woman who did not,” Bowles said. “They always preferred to work with a woman who stayed mum. But it made no difference to the men whether a guy had chosen to negotiate or not.”"