"In the survey, Jane Smith and Dan Jones are pitted against each other in a race for Congress. Both have similar backgrounds, and after reading their bios the survey respondents prefer Jane slightly, 49-48.
"Then they read a second story. In one version of the story, there's no physical description of either candidate, and Jane's lead stays pretty much the same. In a second version, there's a neutral description of Jane's appearance. Suddenly she's 5 points behind Dan. In a third version, there's a positive description of her appearance. Now she's 13 points behind Dan. A fourth version that contains a negative description has about the same effect.
"In other words, any description hurts Jane. And any non-neutral description, even a positive one, just kills her. This is why even a complimentary comment ... is both inappropriate and damaging in a professional setting. It primes people to think of a woman's appearance, and that's apparently enough to keep them from thinking about her actual qualifications. You will be unsurprised to learn that this effect is strongest among men."
Read more at Mother Jones.