Quiz: What goes on in your brain when you're attracted to someone?

Falling in love is like taking cocaine -- at least to your brain. There's a reason why both love and drugs are hard to quit. They activate pleasure centers in your brain that make you crave more.

Because a man's saliva includes testosterone, which increases sex drive in both men and women, a good make-out session can make you feel even more gaga for your guy.

According to prominent anthropologist Helen Fisher, men tend to fall in love more quickly than women, because they are more visually oriented.

Even when we're not looking to have children, our bodies respond to evolutionary urges telling us to mate. That may help explain why many studies have shown that women respond differently to men when they're ovulating. And men respond differently to women as well -- one notable study found that exotic dancers made more tips when they were ovulating.

Researchers have determined that a waist-to-hip ratio of 0.7 is the most attractive to men; that number means that the waist is narrower than the hips. Waist-to-hip ratios between 0.7 and 1.18 would also be attractive; this measurement may indicate physical health and fertility.

Though motorcycles and a nagging mother may drive some women into the arms of a bad boy, birth control pills have been shown to affect women's ability to sniff out good genetic matches for themselves. Studies have shown that women can use their noses to find men who have different genes than their own, ensuring a good genetic mix in any potential children; however, women on birth control were more likely to find men with a similar genetic code more attractive.

"Love map" is a term coined by sexologist John Money, and it refers to an unconscious catalog of traits that we look for in a relationship. When we meet someone, Money posits, our brain goes through the love map determining how well this person measures up.

According to studies, a woman's face and its symmetry is the biggest turn-on for a man.

We're often attracted to people who look, think and act the way we do, which is known as assortative mating.

Enjoy it while you can -- romance doesn't last forever, mainly because our brains can't handle the constant excitement. But that doesn't mean you have to break up; rather, it just means that two people have to work a little bit harder to keep the fire alive.