The secrets of sexual attraction: surprising factors influence which dudes you feel crazy-in-lust over--and who you'll get serious with.(LOVE AND LUST)

* Ever wonder why some guys make you swoon, while others--even cute ones--inexplicably leave you cold? Or why out of nowhere, you suddenly develop a crush on your guy friend? Well, the forces that rule your attractions aren't as random as you think.

While there's no set magical formula to explain why we fall for the people we do, "there are several levels on which people connect, from sociological to psychological," says anthropologist Helen Fisher, PhD, author of Why We Love. "Childhood experiences and biological makeup also play a role in who you're drawn to." Read on for a closer look at the mysterious ways your passions play out.

Understanding Instant Attraction

When it comes to looks, we're hard-wired to dig certain qualities (broad shoulders, facial symmetry) because they indicate good genes. But other preferences seem totally subjective: Some girls drool over tall, lanky blonds, yet others sweat over muscle-bound brunets. What gives?

You could blame that cute guy you pined for in sixth-grade homeroom. "In part, our personal types come from whom we were attracted to when we first had sexual feelings," says psychotherapist Morley Glicken, PhD, author of Ending the Sex Wars. Early crushes--plus characteristics your friends and family or the media emphasize during those preteen years--create a long-lasting imprint. It doesn't mean you won't lust after lots of other dudes; it's just the reason for your gut reaction to certain ones.

Another theory is that most of us are seeking, well, a guy who's kinda like us. "People generally gravitate toward partners to whom they're similar in terms of ethnicity, socioeconomics, education level, and attractiveness," says Fisher. "Even when it's not conscious, you can look at a room of people and figure out immediately who might fit what you want."

The Power of Scent