Hey two-timer, you think you're pretty slick, huh? Think again -- a new study says that women can tell if a man's screwing around just by looking at him.

According to an Australian study published in the Biology Letters' journal, women can detect with an alarming degree of accuracy whether a man is unfaithful just by looking at his mug. Men, however, seem to lack this ability when sizing up women.

"Women's ratings of unfaithfulness showed small-moderate, significant correlations with measures of actual infidelity," said the study, noting that women seem to base this assessment on how masculine a man appears.

Researchers showed 189 color photographs of adult faces to 34 men and 34 women. They then compared the respones to the sexual histories of the subjects and found that females were able to correctly judge infidelity 62 percent of the time. Men, however, guessed wrong 77 percent of the time. (Way to go, guys.)

"We provide the first evidence that faithfulness judgements, based solely on facial appearance, have a kernel of truth," said the study. "It seems remarkable that such impressions have any accuracy at all."

Remarkable, yes. But also bad news for those who prefer something on the side. This doesn't have to be bad news, though: maybe it just means it's time to have the "open relationship" talk with your lady. Who knows, she might be thinking the same thing.