
When many primate females-from chimpanzees to types of baboons called mandrills-become fertile, their estrogen levels peak, opening up their blood vessels and turning their faces bright red. It's an effect that likely stems from biology, says Adam Pazda, a psychologist at the University of Rochester in New York state and an author of the new study. And, if you're lucky enough to get a Valentine's Day card, it will probably come decorated in tiny red hearts. Women have donned pinkish blush and bright lipstick for nearly 12,000 years. Men rate women wearing red clothing as being more interested in sex, hinting that humans may be conditioned to associate the color with fertility. Now, a new study shows how such duds attain their sway.

In a scene from the 1999 sci-fi film, the hero is famously ambushed after becoming distracted by a woman on the street wearing a slinky red outfit.

Red dresses muddle men's minds, just ask The Matrix's Neo.
