The science of love

Using complex algorithms and unusual fieldwork, scientists have discovered the chemical reactions that determine how and why we fall in love. This means big business for matchmaking websites, but does it take the thrill out of romance?

Anthropologist Helen Fisher is being very patient. I have cracked some weak jokes; she laughed politely. I talked too long about myself; she indulged my rambling. And now she’s trying to convince me – with intermittent success – that my relationship isn’t doomed.

Fisher knows something about love. She’s written several books on the science of attachment – that is, the biochemical reactions behind everything from a first crush to a lasting marriage. She has stuck the hopelessly smitten into MRI machines and peered at their brains. She has even popped up on Oprah. And four years ago, she was tapped by executives at U.S.-based, one of the world’s largest dating sites, to study the neurological mechanisms that direct our romantic choices.

There are well over 100 chemicals firing in our brains at any given moment. Some keep our hearts beating, some keep our eyes blinking, and, according to Fisher, four of them – serotonin, dopamine, estrogen and testosterone – help govern a wide range of behavioural traits. These chemicals interact in different ratios in different people, creating what Fisher considers four primary personality types. Each type has a natural match as well as a few decidedly unnatural ones. You can see where this is going.

Armed with her knowledge, Fisher developed a lengthy questionnaire centred on neurochemistry, tested with 40,000 Americans and perfected on more than six million men and women across 35 countries. The questionnaire now pairs up potential suitors on Match’s sister site,, for which Fisher is chief scientific adviser; it can also be found in her new book, out this month, called Why Him? Why Her?, a guided tour through these personality types.

I took the test. It was a lovely, sunny morning. My boyfriend had just made pancakes and, better still, an enormous pile of bacon. I cracked the book open. Am I patient, cautious, domestic? Er, not exactly. (Note: I did not make the pancakes.) Then I can’t call myself a Builder, Fisher’s term for a personality powered by the chemical serotonin.

Would my friends say that I was impulsive, adaptable or obscenely late? Maybe just that last one. It wasn’t looking good for me as a dopamine-fuelled Explorer. And no, I’m not overly trusting, and I’m pretty sure no one’s ever compared me to Gandhi. So scratch the estrogen-driven Negotiator off my list. But analytical, skeptical, extremely competitive? Someone who can be demanding? Was my childhood nickname not Bossy Boots?

I am a Director. My brain is flooded with testosterone. This explains the high cheekbones, the man-sized hands and why I kill at Tetris. (Directors are highly skilled at spatial games.) It also explains why I immediately thrust Fisher’s questionnaire at my boyfriend: I had managed to turn a personality quiz into a competition.

Because he is also competitive, he grabbed a pencil. This should have tipped us off; sure enough, he’s a Director, too. We flipped through the book, learning that Builders pair well with Builders (they’re both devoted to family), Explorers gravitate to Explorers (they seek out adventure), and Directors and Negotiators complement each other’s temperaments.

But our match sounded toxic: “Two Directors sometimes question each other’s facts or logic when they talk, or hurl criticisms that make each other angry. . . . Neither wishes to be intimidated. Both want to win.” So a few weeks later, I was on the phone with Fisher, looking for a little reassurance.

“You’re not doomed,” she said. “There are lots of things that can keep two people together, even though it’s not a natural match. You can work with the problems. You might decide, Well, I don’t think I am going to pick on his logic this time. I’ll just let that one go.” That sounded unlikely. The conversation went downhill. “I don’t want someone always competing with me,” admitted Fisher. “But it might work for you.”

I imagined the website, where millions of estrogen-laden, Gandhi-like Negotiators waited, keen to let me win an argument. I’d have my pick of dating sites, too, each touting its own algorithm for love. It’s big business these days: attracts more than 15 million users, and eHarmony has actually patented its matchmaking formula, which pulls in US$200 million a year from millions of visitors. Here at home, Vancouver’s culls a yearly revenue of $10 million from 600,000 users.

And it’s not just about the money. The study of romance – particularly the study of our brains in various stages of romance – has become a serious academic pursuit. It seems that every year, more lovesick brains are scanned, more sweaty garments are sniffed for pheromone responses, more affairs are cross-checked against menstrual charts. Science stands on the brink of telling us everything there is to know about love. Will we like what we hear?

For all our preoccupation with love, its serious scientific study has often lagged behind sex research. In the 1910s, John Watson first brought arousal out of the bedroom and into the lab; however, the dearth of willing participants meant he had to improvise. “Watson used himself as a subject,” says Mary Roach, author of Bonk: The Curious Coupling of Science and Sex. “He also used the woman he was having an affair with, which caused all manner of complications in his later divorce proceedings.”

Love research, on the other hand, has far less salacious origins. Although it’s now a booming field – with experts across Canadian universities (there’s even a relationship research lab at the University of Waterloo) and scientific studies conducted everywhere from Japan to Brazil – it began, innocently enough, with a monogamous rodent. The prairie vole, a sort of field mouse from the Midwestern U.S., is, along with humans, among the scant three percent of mammals that form exclusive relationships. In 1995, Sue Carter, now a professor of psychiatry at the University of Illinois, found that when prairie voles mate, the hormones oxytocin and vasopressin are released. Additional investigation showed that the brain receptors for these hormones existed alongside those for dopamine – a pleasure chemical associated with ecstasy, focused attention and reward. It appears that the voles remain monogamous because monogamy feels good to them.

With the advent in the ’90s of functional magnetic resonance imaging (fMRI) – a technology that measures tiny metabolic changes in the brain – scientists could begin studying the chemistry of human romance. In 2000, British researchers harnessed this technology to scan the brains of subjects who were deeply in love. They put these subjects into the machine and showed them pictures of their partners, as well as photos of friends. The researchers discovered that a much smaller part of the brain becomes active in love than in friendship. With a surprisingly poetic flourish for a neurological report, they noted, “[It is] fascinating to reflect that the face that launched a thousand ships should have done so through such a limited expanse of cortex.”

Something else stood out. The regions of activity in the lovers’ brains didn’t much resemble those of people feeling other strong emotions, such as anger or fear; instead, they looked like the euphoric brains of people high on cocaine. It would have been sweet vindication for Robert Palmer – cue the swelling synthesizers and the babes in black minidresses, because we might as well face it: We’re addicted to love.

At the same time, Helen Fisher and her fellow scientists in the U.S. were comparing their own fMRI scans of 40 love-addled brains. The results were identical: They found heightened activity in the caudate nucleus, a shrimp-shaped region deep in our brains that evolved more than 65 million years ago. This region is part of the brain’s reward system and helps us to detect, favour and anticipate a particular prize. The more passionate Fisher’s subjects reported being, the more active their caudates.

Fisher also saw activity in the ventral tegmental area, a section of the reward network that she calls a “motherlode for dopamine-making cells.” Euphoria, infatuation, even arousal – chalk all these feelings up to dopamine. And dopamine-saturated areas of the brain are home to our oxytocin receptors, which means that, just like our faithful prairie-vole friends, we think monogamy feels pretty good, too.

In that first flush of love, when we can barely eat, and sleep even less, the brain turns into a see-saw of chemical reactions. Dopamine goes up. Levels of serotonin – the compound thought to help control obsessive-compulsive disorder – go down. Little wonder you can’t get him out of your head. Testosterone levels increase; you find yourself lustily eyeing the bedroom. Once there, touching and orgasm release a flood of vasopressin and oxytocin, the chemicals associated with attachment and trust. (Kissing also elevates levels of oxytocin in men, but not in women. It seems we need more than a little smooching to feel connected.)

Lust, love and attachment: All are accounted for in our frenzied brains. According to Fisher, that’s because these are three neurological drives as potent as hunger and thirst, each serving to control a different aspect of reproduction. Lust emerged to encourage us to get frisky with almost any suitable sexual partner. Because that can be exhausting, romantic love developed so we would focus our efforts on one partner. And since a baby’s chances of survival would improve with two parents, attachment evolved to keep our ancestors together.

These reproductive drives might also account for the differences Fisher perceived in male and female brain scans. Unsurprisingly, men showed more activity in regions associated with visual processing, especially of the face. This may be because shiny hair, smooth skin, white teeth and a strong body all indicate a healthy woman with good child-bearing possibilities. (It may also explain why more Canadian men than women say they believe in love at first sight.) On the other hand, it was only women who demonstrated activity in regions of the brain associated with the retrieval of memories. It’s no easy task to raise a kid, so it’s important to remember, in Fisher’s words, “whether [your mate] can hit the buffalo on the head and share the meat with you.”

It would seem, then, that the three reproductive drives progress quite tidily from each other: Lust begets love begets attachment. Not so fast, says Fisher. “I don’t find them phases; they’re brain systems,” she explains. “You can fall madly in love with someone you’ve never slept with, you can go to bed with someone you could never love, and you can feel deeply attached to a college friend and, years later, it turns into a romance. So you can start with any one of these brain systems and have it develop into others.”

But it appears as though the brain can be tricked. Danger triggers adrenalin, a stimulant closely related to dopamine. In one experiment, researchers wrangled dozens of men into crossing Vancouver’s Capilano Suspension Bridge, which teeters 70 metres above a rushing river. At the centre stood an attractive woman, who handed them a basic questionnaire and then passed out her home phone number, telling the men to call with any questions. The experiment was repeated with new subjects on a low, secure bridge. More than four times as many volunteers from the suspension bridge called the woman. Those breathless boys thought they were experiencing the thrill of new love, but it was really just the rush of standing on a plank of wood more than 20 storeys high.

And couldn’t a casual one-night stand – with its groping-induced release of oxytocin – prompt unexpected feelings of attachment? Fisher isn’t convinced. “We’re not simply puppets on the string of DNA; biology and culture are constantly interacting with each other. A person who’s prone to alcoholism can give up drinking.” She points out that, in the heady moments of sex or love, there are many systems working together. “The cortex is assembling data and making decisions; the limbic system is feeling various emotions; and then there are the basic passionate drives.” Turns out our brains are better at distinguishing between lust and love than we might think.

“Don’t forget, somebody has to fit with what you’re looking for in a mate,” Fisher says. “You can drive up dopamine in the brain just by taking cocaine. But if you’re kissing a frog, you’re kissing a frog.”

So we aren’t cavemen worried about surviving the cold winter or passing along our DNA before that 30-year life expectancy kicks in. But love still can, in some cases, be a matter of survival, with implications for our financial well-being and the longevity of our relationships.

Studies have shown that during ovulation, a woman appears more attractive to men and tends to be guarded more vigilantly by her partner. From a cold Darwinian perspective, that sounds about right: She is signalling her fertility, and, if a man doesn’t want to raise another guy’s baby, he’d better keep his woman close.

Researchers from New Mexico took this show on the road, looking for the “first real-world economic evidence of male sensitivity to cyclic changes in female attractiveness.” On the page, that sounds dryly academic; in reality, they headed for a gentleman’s club. The team asked lap dancers to monitor their menstrual periods, their work shifts and their tips for 60 days. The results are astonishing. Ovulating dancers pulled in US$70 an hour; those in the middle of their cycle made $50; and menstruating dancers took home a lowly $35 an hour. Now here’s the caveat: Those are the statistics for normally cycling women. Dancers who took the birth-control pill saw no mid-cycle increase in their tips. But Pill users made an average of only $193 per five-hour shift, while the other women pocketed $276 – which means that patrons found them less attractive to the tune of 16 bucks an hour.

It gets worse. Women are particularly responsive to olfactory cues, and researchers wondered if that might serve a reproductive purpose. Our chances of giving birth to a strong, healthy baby increase if we partner up with someone who has a different immune system from ours. So a team of Swiss scientists handed women a stack of sweaty T-shirts and asked them to take a whiff. Normally cycling women consistently preferred the smell of men with immune systems that were distinct from theirs. Women on the Pill picked the wrong shirt.

As if genetically compromised babies weren’t bad enough, couples with similar immune systems have a host of relationship problems to look forward to. As the proportion of similarity increased, women’s sexual satisfaction decreased, their number of affairs increased, and their attraction to men other than their partners increased – particularly during ovulation.

The Pill gave women sex without fear, but it may have come at a cost. Even scientists are now advocating that consequences of the Pill “need to be known by users.” We already have warning labels on cigarettes – those dramatic pictures of bleeding lungs – so why not on your pack of Yasmin? I suggest a lap dancer looking forlornly at her paltry pile of tips.

But adultery omens and lap-dance economics aside, why do we study love? Fisher’s reasons are fairly pragmatic. “It’s totally fascinating, and it’s very central,” she says. “But why do I study it? Because it’s there.” Bonk author Mary Roach pushes this argument further: “People are endlessly confused, flummoxed, depressed; they feel that love pulls the rug out from under them. There’s a tendency to want to control it and understand it, so you turn to science for the answers.”

Yet many of the scientific observations made about love sound mighty familiar. It drives us to sheer heights of ecstasy? The Romantic poets had that covered back in the 19th century. It’s an addiction as powerful as any drug? Those cowboys in Brokeback Mountain couldn’t quit the habit. When we’re separated from our beloved, dopamine levels go through the roof, causing anxiety, fear, even violence? Three words: Romeo and Juliet. Before a man with a microscope or a woman with an MRI machine stepped onto the scene, the task of explaining love fell to the poets and the playwrights – and they did a decent job of it. Scientists are now able to corroborate what artists have already intuited. To do so, they’ve taken the metaphor and turned it literal; chemistry is no longer just an enigmatic spark between two people but a neurological network that lights up our brains like a Christmas tree.

So why isn’t the metaphor good enough? Literature offers a window into the messy lives of others; it prompts that shock of recognition; it helps us feel, emotionally and intellectually, a little less alone. Still, because we want something more concrete, perhaps that’s why we find the idea of a scientific formula for partnership so seductive. It’s the closest thing we have to a guarantee.

But there is a wonderful mystery to why two people come together that I don’t think the poets or the scientists will ever truly resolve. Maybe that’s just my testosterone-fuelled, Director-like skepticism talking. Maybe my boyfriend does lack sufficient estrogen levels for our relationship to last, and maybe that will be of some consolation if it ever crumbles. But he provides pancakes and we lose entire days to conversation and, sure, we fight fiercely but we make up well. That’s plenty Love Potion No. 9 for me.

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