Finally, those brainiacs in the scientific world have hit on something really earth-shattering (and we don't mean global warming). We're talking about personality typing. "Almost every man falls into one of four categories," says Paul Dobransky, MD, author of "The Secret Psychology of How We Fall in Love." Reasons for the differences range from hormones to psychology, and knowing the types gives insight into a guy's dating MO.

We had Dr. Dobransky, founder of kwml.com, and anthropologist Helen Fisher, PhD, chief scientific adviser for a new online dating site, break down each type. Use this info to analyze guys, have more fun with yours, and even reach soul-mate status.

Typical interests: Organized groups (like a running club), gadgets, nonfiction books

When he's stressed, he analyzes the situation and makes lists and plans.

He lights up if you say: "I could really use your advice on something.

You want your boyfriend to be a supportive, steadfast partner who shares your sensible approach to life and is smart enough to get your sometimes quirky side without judging.

You're turned on by witty, intelligent conversation and gifts that show the affection he's not so great at verbalizing.

You deal with problems by talking about them rationally. This guy's always game for reasoned debates, but drama queens will lose big -- emotional outbursts freak him out.

His favorite dates: He feels most energized when he's engaging his mind, so try watching a documentary, seeing an interesting exhibit, or taking a class, such as sushi making.

Relationship requirements: This dedicated dude gets totally absorbed in his interests. If you don't even ask about them ("How was Shark Week?"), he'll feel like you don't get him. He's also tuned in to etiquette, so gaffes (like bailing on plans) turn him off.

What he seeks in a soul mate: To really trust you, he has to know that you respect his cerebral nature. Help coax out his playful side with plans he'd never make on his own and he'll see you as the total package.

Typical interests: Sports (playing and watching), barbecuing, building things

When he's stressed, he dives in and deals with the cause, whether it means extra hours at work or a showdown.

He lights up if you say: "Is there anything you can't make happen?"

You want your boyfriend to be the classic male archetype -- a protective, take-charge dude who doesn't yap about his feelings but lets his guard down when alone with you.

You're turned on by grand gestures, like spontaneous PDAs, and manly deeds, like changing your car's oil.

You deal with problems directly without any passive-aggressive BS. He's quick to confront conflict. If you are too, your issues will disappear once you hash them out.

His favorite dates: His heart beats faster (figuratively and literally) when he's active, so suggest a hike in the woods or a boxing class followed by drinks.

Relationship requirements: This on-the-go guy needs solo time to recharge and will feel smothered if you are clingy. You'll need a thick skin, because he doesn't sugarcoat things...ever.

What he seeks in a soul mate: His he-man side needs you to appreciate his efforts to lead. But under his strong, silent exterior, he's a superloyal softie. He feels complete when you can talk about the feelings that he internalizes.

Typical interests: Outdoor activities (like camping and skiing), foreign travel, parties and crowds

When he's stressed, he distracts himself with something amusing, like watching the game or organizing a social outing.

He lights up if you say: "Oh, you have a fascinating story about that -- c'mon, tell everyone."

You want your boyfriend to be a whirlwind of personality who can liven things up, make you laugh, get you out of your head, and keep you guessing...in a good way.

You're turned on by unpredictable, exciting plans.

You deal with problems in a casual, nonconfrontational way. Mr. Conflict Avoidance hates when you're unhappy with him and will deflect attention unless you tackle the issue.

His favorite dates: This class clown loves being around new people -- think karaoke night or a charity casino event. He's also thrilled by new accomplishments, like scaling a rock wall at the gym.

Relationship requirements: He needs a laissez-faire chick who won't try to rein in his inner wild child. He is willing to share the spotlight, just not all of it.

What he seeks in a soul mate: The ultimate people person bonds best with an ever-evolving woman who can match his lust for new experiences. He craves independence yet still needs to know he's important to you, so being secure enough to show you care is a must.

Typical interests: Music, cooking dinner for friends, reading literature

When he's stressed, he talks about it with confidants until he finds a solution.

He lights up if you say: "I never would have noticed that. You're so observant!"

You want your boyfriend to be a guy who truly listens, understands your girlie side, and can talk about feelings.

You're turned on by sweet, movie-worthy romance, like slow kisses and crazy-great compliments.

You deal with problems by honestly addressing them and taking emotions into consideration. He's a philosopher at heart, and even if you two don't agree in the end, you'll learn tons about each other during your in-depth discussions.

His favorite dates: Atmosphere matters to this sensualist, so find a spot with a romantic vibe (try a botanical garden or outdoor jazz concert) for the real highlight: your ever-intensifying one-on-one bond.

Relationship requirements: This nurturer tries to know everyone he meets on a deeper level, which can be rough if you're the jealous type. Also, he's so into connecting that he'll feel dissed if you don't share your problems.

What he seeks in a soul mate: This idealist falls when he knows you value communication too. Because he tends to ruminate, you'll enhance his life by being decisive yourself.