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The science of love

F.Birchman /
/ Source: contributor

Consider, this Valentine’s season, what we would think of attraction, desire, sex and love if the scientists got hold of it. Take, for example, the story of Sam and Margo who meet in the local grocery store. (Warning: If you’re the hearts-and-flowers sort of romantic, you might not want to read any further.)

There, by the bunches of cilantro, an herb that confuses Sam, he first sees Margo. He notices two things about her. First, she seems to understand cilantro, and second, she’s hot. How does he know she’s hot? Is it that certain spark? That mysterious “connection”?

Probably not, says Robert Kurzban, a University of Pennsylvania psychology professor. It’s her body mass index, or BMI. Then, when she turns around, it’s her facial symmetry.

According to Devendra Singh, an evolutionary psychologist at the University of Texas, it’s her waist-to-hip ratio which, in Margo’s case, is the ideal .7.

After using “speed-dating” events as his lab, Kurzban has concluded that “there is a consensus about what counts as attractive,” and, for men, it is based on BMI and facial features. For women it is based on BMI and cues about health and social status like income and education.

Though we like to think this initial attraction can only be explained by Renaissance poets and 80s hair bands, it’s evolution. Sam is looking for clues about Margo’s fertility, health and youthfulness, traits that mean she’ll produce good babies. There’s even some science that says a woman’s face becomes more attractive when she ovulates.

Margo is looking for signs Sam is virile, strong, healthy and a good provider.

Lucky for Sam, he did not wear his Slippery Rock sweatshirt to the store. He’s come from work. He looks successful, though he’s really just got a thing for fashionable clothes. He’s actually broke. But Margo doesn’t know this and so she agrees to go out.

Sam thinks he’s hit the jackpot. As neurobiologist Steven Pinker has written, “Somewhere in this world of 5 billion people there lives the best-looking, richest, smartest, funniest, kindest person who would settle for you.” Sam believes he can’t do any better than Margo, though if he thought he could, he might be hanging out at exclusive clubs where the lingerie models drape themselves over the bar.

Addicted to love
Something happens to Sam and Margo as soon as they size each other up. Chemicals begin seeping into their brains. They begin to feel good. They flush. They’re happy and excited. And then, a short-time later, Sam finds himself looking across a candlelit dinner table at Margo who has a tail of linguine dangling between her lips, and he decides right then that life simply cannot go on without her.

“Men fall in love faster than women,” explains Rutgers University anthropologist Helen Fisher, author of "Why We Love: The Nature and Chemistry of Romantic Love."

“They are so visual," she says. "That’s why the whole porn industry is built around them.”

The next day, Sam calls Margo for no good reason. He just wants to hear her voice. She calls him 5 minutes later to say that the previous 5 minutes were the longest of her life.

The word “pookie” is exchanged.

Sam tells his friends that he has to skip the all-male, beer-soaked Super Bowl party — and their annual “rate-the-cheerleaders” contest — because he has “umm … other plans.”

This behavior is completely out of character for Sam. It’s crazy, is what it is. It’s like he’s on drugs or something.

Which, in a manner of speaking, he is. Where Shakespeare says, “Shall I compare thee to a summer's day? Thou art more lovely and more temperate,” Fisher says, “group activation specific to the beloved under the two control conditions occurred in dopamine-rich areas associated with mammalian reward and motivation, namely the right ventral tegmental area and the right postero-dorsal body and medial caudate nucleus. Activation in the left ventral tegmental area was correlated with facial attractiveness scores. Activation in the right anteromedial caudate was correlated with questionnaire scores that quantified intensity of romantic passion. In the left insula-putamen-globus pallidus, activation correlated with trait affect intensity. The results suggest that romantic love uses subcortical reward and motivation systems…”

This is Sam’s brain on love.

Fisher believes that we become, as Robert Palmer sang, “addicted to love.” “And that’s why I advise people to wait until the passion wears off” before marrying, she says.

When reality sets in
And the passion does wear off, made-for-TV movies not withstanding. Fast forward a few years and we find Margo staring at the tattered remains of the kitchen remodel project Sam started during the last presidential election — which, coincidentally, is the last time they had sex. She recalls the names of good divorce lawyers.

Sam, meanwhile, has caught himself staring wistfully at Shari, the 23-year-old personal trainer at his gym. Shari probably would not insist Sam explain the rules of football when the score’s tied with 25 seconds left in the fourth quarter. She might still like sex, too.

Fisher has seen patterns of divorce and separation peaking at about four years. This happens in all cultures she’s studied.

(Should this Valentine story end with a happy ending, or not? I’d prefer an unhappy ending myself, because I hate Valentine’s Day and its manufactured romance. But then, I couldn’t explain the concept of happy ever after. A dilemma …)


Despite his wandering eye, Sam cannot imagine living without Margo. Though Margo does fantasize about trading sex with a hunky carpenter who could finish the damn kitchen, she looks at Sam and sees her man. They have formed a bond.

Bonded and determined
According to Fisher, our brains literally become rewired when we form pair bonds. The genetic basis of our personalities plays a role, too. Some people, those Fisher calls “explorer types,” have a serotonin system that seeks constant change. They’ll be less likely to stick it out through rough patches.

But Sam and Margo aren’t explorers. They come to learn that love, lust and romance all wax and wane. Sometimes you just have to grit your teeth, even when you think love has gone.

“The conscientious, those who have trust and loyalty are more determined to maintain a long-term relationship,” Fisher explains.

It takes work. But then so does everything worthwhile.

Love, romance and desire have to be nurtured; we can’t rely on those brain chemicals for long. Love can be an exercise in sheer determination. Which, if you stop to think about it, makes the whole thing more romantic, not less, and a far better Valentine’s gift than cheesy lingerie she’ll never wear. 

Brian Alexander is a California-based writer who covers sex, relationships and health. He is a contributing editor at Glamour and the author of "Rapture: How Biotech Became the New Religion" (Basic Books).

Sexploration appears every other Thursday.