Love doesn't just inspire sonnets, it may also ensure some species' survival, says University of Illinois at Chicago neurobiologist Sue Carter, PhD. For instance, feelings of warmth and attachment encourage people to marry and share child-rearing duties, she adds. And humans aren't the only animals to take advantage of monogamy. Prairie voles-tiny field mice native to the American plains-also pair up and live together for a lifetime. These animals may be driven by hormones and impulses much like our own, Carter explains.

"The purpose of love is survival and reproduction," says Carter. "Knowing that, we also get insights into the mechanisms...and hormones that cause social bonds."

Carter will share her insights on monogamy and its biological underpinnings on Saturday, Aug. 18, at 11-11:50 a.m. at this year's APA Annual Convention. Her Board of Scientific Affairs-sponsored talk is titled "Molecules and Monogamy: What's Love Got to Do With It?" One such insight is that social monogamy-living together and sharing everyday tasks-may be more important than sexual monogamy. Carter and her colleagues have observed that vole pairs spend most of their time together, and take turns babysitting and foraging for food. However, they do mate with other voles if given the chance.

"What you have is a system...that favors genetic diversity but at the same time gives you the benefit of social monogamy," Carter says.

Human monogamy may not be all that different, she adds.

In her talk, Carter will also note that while many people assume that marriage is a fundamentally cultural institution, prairie vole research suggests that it may have deep biological roots. One such root is the hormone oxytocin. Both new human and sheep mothers have elevated levels of oxytocin coursing through their veins. And the effect isn't just correlational: If you give a sheep a shot of oxytocin, she will mother an unrelated lamb. Give college students an oxytocin boost, and they will be more likely to trust strangers, Carter notes.

Oxytocin studies are important, says Carter, in part because pregnant women at risk for premature delivery are sometimes given oxytocin blockers, which stave off labor but could also have long-term effects. One study by Carter, published in Developmental Psychobiology (Vol. 44, No. 2, pages 123-131) found that exposing male prairie vole pups to an oxytocin-blocker at birth diminished their parental instincts later in life. However, the picture is complicated-large doses of the hormone sometimes have the opposite effect of smaller ones.

Such research, says Carter, is just a taste of what prairie voles have to teach us about love.

"Their lives are so interesting," says Carter. "It's surprising how highly social a small rodent can be."

-S. Dingfelder