Your mom probably taught you that if you don't have anything nice to say, you shouldn't say anything at all.

That's great advice when it comes to dealing with annoying relatives and unpleasant acquaintances, but it's a terrible approach to management. Your team's advancement depends on them receiving regular, honest feedback from you about their performance.

In this context, excessive niceness isn't a virtue, but a problem, and it turns out it's a particular problem for professional women. New science reveals that bosses are less willing to deliver honest, useful feedback to female subordinates.

The unintended consequences of being nice

That's what Dr. Lily Jampol, a lecturer at Queen Mary University of London School of Business and Management told a Google re:Work event in 2014 in a talk outlining her research. Jampol and her confederates asked volunteers to rate "student" essays that were actually computer generated and of equal quality. Participants were told one essay was by "Andrew" and another by "Sarah."

Can you guess which fictional student got more honest feedback? Yup, "Andrew."

Jampol discovered that "Sarah's" essay, despite being essentially identical, was rated 15 percent higher by evaluators. That kind of niceness might initially sound appealing to female college students hungry for A's (and, teachers and professors, you might want to watch out for this bias too), but it's bad news in the long term if it deprives women of the honest feedback necessary to improve.

Why do bosses behave this way? Giving negative feedback is always difficult and it can be even trickier to be blunt with female employees because of often unconscious cultural baggage that suggests women might be less able to take the unvarnished truth.

"Women have stereotypically been seen to be less competent than men but also more emotionally unstable and vulnerable, and these beliefs, despite being often subconscious or implicit, can lead to protective or sometimes even patronizing attitudes and behaviors towards women," Jampol explains.

How to give more honest feedback

If you don't want to fall into this trap of inadvertently holding back the talented women on your team with well meant but condescending white lies, Jampol's talk below offers advice to ensure your feedback is consistently fair and honest. Other experts have also weighed in on the subject, suggesting their own tips for better feedback, as well as tricks to be forthright while still being kind.