There are a lot of reasons why a guy might keep his lust for you on the down-low. Maybe he's a coworker, your teacher, a good friend, or a friend of an ex-boyfriend. He can try to hit it, but the truth always slips out. You just have to know what to look for.

Sign #1: He acts like he has OCD when he is around you.

Talking to a hot girl is enough to make most guys a little nervous, and the fact that he's trying to conceal his attraction amplifies the effect. He'll attempt to release that pent-up tension by fidgeting, talking fast or rapid eye movements. Look for tip offs, like him picking at his nails, peeling the label off his beer bottles, shredding his napkin, or adjusting his clothes. All of which may mean he's totally smitten (or just in desperate need of a Xanax).

Sign #2: He sounds like Russell Crowe... or a Disney Character

Women are instinctively attracted to men with deep voices and accents, since the lower pitch generally indicates desirable traits like strength and dominance. Without realizing he's doing it, a guy who is interested in a women might suddenly lower his tone. Thanks to his primitive instincts, he may also become extra-expressive and animated in order to capture your attention.

Sign #3: He Gives other Dudes the Simon Cowell Treatment.

A guy who typically never has a bad word to say about anyone will use terms like wuss, loser, or player to describe other men when in the presence of an enticing female. He'll target guys who the women may seem interested in, often pointing out how they'll screw you over. He wants to reduce your dating pool by knocking potential partners out of the running. He's also implicitly attempting to make you realize what a great catch he is in comparison. His put-downs basically translate into, "That guy's a total douche bag... unlike me."

Sign #4: He Switches into Stand-Up Mode.

This is a big one. When a guy likes you, hell crack more jokes than Dane Cook. His plan is twofold. He hopes to impress you by showing off how witty he is and subtly suss out if you have a thing for him too. A women is more likely to laugh at a man's joke if she's attracted to him, studies show. So if a women squirts beer out of her nose in response to a man's funny jokes, he'll get psyched and ramp up his comedy routine even more.