I'm pretty sure love is the most powerful force on earth. Why else would I leave my sunny home in San Diego and my no-strings bachelorhood to move to Olympia, Washington, to be with a woman…and her seven-year-old? Back in the day, if you'd told me I'd eventually do this, I would have instructed the bartender to cut you off. Yet there I was, driving little Ashley to swim lessons. Love is a powerful thing—but it's also the least understood force on earth. Why do we do all these crazy things in its pursuit?
I'd been writing about this question for years. Then I met Emory University scientist Larry J. Young, Ph.D., a pioneer in the field of social neuroscience, the study of what goes on in our brains when we interact with other people. We wanted to explain this puzzle, and examined everything from prairie vole "love" to human sex lives. The result is a book we expect to be controversial: The Chemistry Between Us: Love, Sex, and the Science of Attraction. Our premise is simple—every behavior related to love, sex, and intimacy starts in the brain, and we have much less control over these behaviors than people think. Here, some of the relationship truths Larry and I uncovered:
On sitcoms, after a split the man typically finds some new girl to flirt with while his ex sits around, sobbing into her Häagen-Dazs. But in real life, men don't move on so easily. Why? Thanks to a neurochemical called vasopressin, men in crisis are more likely to see other men as less approachable, but that same chemical cues women to see other women as more approachable. This is called tend-and-befriend behavior, and it means that while you're being soothed by your girls (who are probably saying that you're gorgeous, and that your ex is a dick), the guy is dealing alone—and having a harder time of it. Another reason men fare worse in breakups? They regard their lover as "home." (I'll explain why in a second.) So a man doesn't just lose the woman he loved; he becomes emotionally homeless. No wonder guys can suffer more severe health consequences than women after a split: Studies have shown that divorced men have lower immune function than married men do, and they're statistically more likely to be hospitalized or even die earlier (yikes!) than divorced women.
Sex makes both men and women feel attached.
It's a misconception that women get super connected to the people they sleep with but that men never do that "needy" emotional thing. In truth, sex releases bonding chemicals oxytocin and vasopressin into female and male brains, and it's vasopressin that helps a man bond with you. For an animal-kingdom example, consider the usually monogamous male prairie vole, a cute little mouselike creature. Larry and his colleagues discovered that without the vasopressin effect, the vole would turn into a promiscuous cad. No vasopressin effect, no monogamy. When a human male is under the influence of vasopressin, as all are during sex, he forms a bond with you that's kind of like an animal claiming a home; your scent, your eye color, even your apartment all become cues that make him crave you. Another animal example: If you give a male hamster a shot of vasopressin to the brain, he'll run around peeing like crazy to mark territory—that's his place, nobody else's. Release a guy's vasopressin by having sex with him, and he'll unconsciously start to view you as the territory he's bonded to. You don't have to like it, but this is where much of that famous male possessiveness comes from.
Your brain thinks your boyfriend is your baby.
I know that headline sounds nuts, but hear me out! When a mother gives birth, the cervical and vaginal stimulation immediately releases oxytocin in her brain, which contributes to feelings of reward and motivation. This phenomenon is one of the things that helps a new mother see her baby—whom others might regard as a pooping snot factory—as the most precious thing ever. But get this: When a man and woman have sex, the stimulation activates much of the same circuitry. Just as a new mother associates her pleasurable emotions with her baby's face, this circuit prompts a woman having sex to look at the man, register his face as trustworthy, and associate that specific face with the pleasure she's feeling. In fact, studies have shown that when women look at pictures of their romantic partners and pictures of their children, the brain patterns actually overlap. We believe this is why women tend to nurture their lovers while men tend to protect theirs.
Size really does matter.
Scientists used to think—and some still do—that the only job a penis had was to deliver sperm. But why, then, has it evolved to be so much longer than necessary? (The average erect non-porn-star penis is about five inches, but it only takes a two-and-a-half-inch one to get you pregnant.) We believe it's because the human penis is also built to trigger that release of oxytocin in a woman through cervical stimulation. Does that mean that average (and larger-than-average) guys could have more luck getting women to fall in love with them faster? Well, a large penis isn't required in order to have a strong connection with someone—but yes, we think it could help!
Love is an addiction (but sex isn't).
No doubt you've heard a lot about sex addiction lately, thanks to guys like Russell Brand and David Duchovny, but I believe that phenomenon is more likely a form of obsessive-compulsive disorder (which is a whole different story!). Love, on the other hand, is an addiction. Passion fades over time because the brain's reward system physically changes in the same way it does for a heroin addict: Its receptors for dopamine, a neurochemical that triggers euphoria, are altered, and in place of the rush, you feel more of a need. You must have your partner just to avoid feeling miserable. Even though being with him or her produces less pleasure than at the beginning, being without him or her produces a feeling of loss. Sigh.
When you're on the Pill, it can weaken his sex drive.
Here's the deal: Men can sense ovulation. Your man may not know he's sensing it, but he is more likely to unconsciously engage in what scientists call mate-guarding—interrogating you about where you're going, snooping through your purse, asking about your cute male coworker. His brain is telling him that now's the time you can make a baby, and that if there's any baby-making to be done, he's going to be the one to do it. Scientists are still trying to discover exactly how men pick up on this timing—it might be slight changes in your body shape (breasts become a little more symmetrical), color (skin lightens), or voice (it gets higher). Pheromones may also be involved; in one study, guys judged the scents of women near ovulation to be sexier. But the point is this: When you're on the Pill, you don't ovulate, so you miss out on this unconscious hotness boost. Scientists have found, for instance, that when strippers were ovulating, they made about $90 more per shift than at other times in their cycle—while strippers on the Pill never got the pay bump. Don't go throwing out your pack just yet: There are other factors to male libido, like not worrying about getting you pregnant!
When I first embarked on this journey with Larry, I was a little disturbed that a few chemicals in my head had so much influence over my life. But then I remembered some of my past shenanigans—yes, I'm talking about you, former Chicago Bears cheerleader—and I felt relieved to know there was a reason for my lack of reason. Besides, if we weren't wired this way, we'd never fall in love, and we wouldn't be driven to have sex, and there would never be any babies. Evolutionarily speaking, that's why all this chemistry exists. So what if it makes us go a little nuts sometimes? It's also the gift that delivers the greatest joys of life. So go ahead. Open it. There are happy surprises inside.
Brian Alexander is a former Glamour contributing editor. An award-winning journalist, he's also written several books.
