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What do we mean when we talk of love?
Just in time for Valentine's Day, psychologist Dacher Keltner demystifies the biological manifestations of everyone's favorite heartfelt emotion

| 13 February 2008

Though love attains holiday status but once a year, for social psychologist Dacher Keltner the feeling is more than a passing fancy. Keltner, co-director of the campus's Greater Good Science Center, has long investigated the underpinnings of human relationships, which in addition to love include sympathy and gratitude.


Dacher Keltner (Wendy Edelstein photo)
 

Love is in the air this week, and also in the mail - the U.S. Greeting Card Association estimates that a billion valentines are sent worldwide each year. So it's appropriate that today, Feb. 14, Keltner will discuss the emotion that has inspired bards throughout the ages at a Valentine's Day Tea at International House. For him the word love conjures up more than the romantic connection characteristic of long-term partnerships. There's also the love between parent and child, the passion for one's sexual partner, and the love between non-kin, most typically in friendships.

"Love" is used to describe a variety of relationships, in other words, and Keltner notes that it can be imprecise. "People say, 'I love my children. I love my partner. I love my car. I love ice cream. I love the spirit of Berkeley,' " he offers by way of example.

What's more, various kinds of love activate distinctly different areas in the brain. When romantic love takes hold, "you feel trust toward that person," says Keltner. Those feelings reside in the brain's reward centers - the ventral anterior cingulate, the medial insula, the caudate, and the putamen. Romantic love actually deactivates the brain's threat-detection centers - the right prefrontal cortical regions and the amygdala - enabling committed partners to see their beloved through rose-colored glasses.

By contrast, desire - the passionate love that ignites sexual relationships - manifests in the brain's traditional reward- and pleasure-processing centers. And when you show parents pictures of their babies, yet another region of the brain comes into play.

While desire may serve as the impetus for promiscuous coupling in other primates, in humans the impulse propels us to form monogamous pairs - at least, that's true for most of us, says Keltner. "From an evolutionary viewpoint, it's very interesting that humans differ from other kinds of primates in that we like to form these long-term pair bonds." Our reasons for doing so are rooted in evolution, he says, "because our offspring are vulnerable and enormously demanding in terms of requiring basic care to survive."

In the love lab

In his lab, Keltner has tracked both the behavioral and biological manifestations of love. Observe a newly smitten duo versus an established couple and you'll see different nonverbal cues, he says. Long-term couples engage in head tilts, open-handed gestures, and warm, friendly smiles. "When they show that behavior toward their partner, they're feeling love but not desire," he explains.

People feeling sexual desire, on the other hand, use lip cues (such as lip licks and puckers) and lip and tongue protrusions to express their feelings. And couples who show more nonverbal displays of love - versus desire - are more likely to discuss a future together, says Keltner. On the other hand, those pairs feeling desire's tug are less likely to talk about plans beyond their next rendezvous.

The differences don't end there. Keltner and his colleagues wanted to find out whether romantic love (based on devotion and trust) and desire would map to oxytocin, a hormone released in the brain and bloodstream when triggered, for instance, by a welcome touch or eating chocolate. To research these questions, they asked a group of women (who have seven times the level of oxytocin in their bloodstreams than men do) to describe a time when they felt intense connection and warmth toward someone. As the women talked about their experiences, Keltner coded their nonverbal cues of love (as opposed to desire's various lip cues) while measuring the presence of the hormone. Only the love cues caused oxytocin to release in the bloodstream, he reports.

Good vibes writ large

For Keltner, who looks beyond the intrapersonal functions of emotions to their social utility, such findings potentially have broad applications. Loving one's child or spouse differs from experiencing that emotion for strangers, says Keltner. Love of humanity is the centerpiece of diverse ethical traditions - agape in Christianity as well as many of the ideas in Tibetan Buddhism, he says.

When Keltner talks about love of humanity, he means a community-focused love, one in which Jesus' basic teachings come to life: "The real test," he says, "is giving to people in need who are non-kin." Ask people to talk about situations in which they felt such love, he says, and they use language like "I looked in his eyes and felt a deep connection and devotion." He's particularly struck by the observation that when people describe their loving response to a stranger they uniformly report, "I really believe human beings are good."

Where does the impulse originate to love and care for other people to whom we are unrelated? "It's a bit of a mystery," admits Keltner, though he adds that "for hundreds of thousands of years we evolved in small groups that had a lot of non-kin relations." For example, in hunter-gatherer cultures, mothers relied upon non-kin to help care for their children when they went to forage for food.

"Is love of humanity a derivative of romantic love? Is it some offshoot of caretaking love? We don't know, but it's pretty clear it's a universal and does a lot of important work related to building strong groups."

Keltner points to the work of Paul Zak, professor of economics and the founding director of the Center for Neuroeconomics Studies at Claremont Graduate University, whose research indicates that oxytocin "is the biological catalyst of trust."

Zak conducted an economic trust game via computer in which an "investor" receives $10, and then is asked how much, if any, money to give to a "trustee." The value of the funds received by the trustee triples, and that participant then gives as much or as little money back to the investor as he or she wishes.

In Zak's studies, conducted in Germany and Switzerland (where it's legal to use oxytocin experimentally), the economist gave "investors" either a blast of oxytocin or a neutral solution via a nasal spray. Investors who received oxytocin were twice as likely to give away maximum amounts of money as were those given the neutral spray. "Zak's work," Keltner says, "shows that in countries where citizens trust each other, social indicators such as well-being tend to be higher. The likely mechanisms are that trust facilitates generosity and cooperative behavior, which build healthy, long-term bonds."

Although Keltner is sanguine about human nature, he's concerned about America's lack of trust toward its citizens as well as the dearth of brotherly love in our country. Trust in America - both the government's trust in its citizens and the citizenry's trust of one another - is on the decline, notes Keltner. "If you randomly surveyed people from different countries and asked, 'Do you trust your neighbor?' we're very low on that measure," he says. Countries such as Norway, China, and India - that are thriving economically - have high levels of trust among their citizens. Where there's a trust deficit, he observes, "you sue someone instead of negotiating. If you trust your fellow citizen, you're not pulling the trigger."

Two of Keltner's areas of interest, economics and evolution, hold cynical views of human nature. The former assumes "we're just self-interested gratification machines," he explains, while the latter sees people as a collection of "selfish genes." Upending such dire beliefs is motivating, says Keltner. "Our research shows that altruism is everywhere. People are so wired up to give to others and take pleasure in that."

The "Love of Humanity" Valentine's Day tea with Dacher Keltner will take place today, Feb. 14, from 3 to 5 p.m. in International House's Great Hall. For information, call 643-4128.
For information about the Greater Good Science Center, visit peacecenter.berkeley.edu.