Thanks, Mom!

There are plenty of reasons oxytocin is referred to as the cuddle chemical. Levels of the hormone surge during caresses, and researchers think it evolved as a way to reduce stress and fear of others long enough to enable contact necessary for procreation. It also helps facilitate bonding between mothers and newborns. But for the first time, scientists have found that Mom's innate ability to soothe — and to boost oxytocin levels — is as powerful whether she's offering a hug in person or consolation over the phone.

To understand how mothers can influence levels of oxytocin in their children, researchers at the University of Wisconsin-Madison's Child Emotion Lab recruited 61 girls, ages 7 to 12, and placed them in a stressful situation: they had to give an impromptu speech and solve math problems in front of strangers. Afterward, some girls were allowed to seek refuge in their mothers' arms, others talked to Mom on the phone, and the control group watched an emotion-neutral film (March of the Penguins) that bored many participants to sleep. (See iPhone apps for new moms.)

The results, published in May in the biological-sciences journal Proceedings of the Royal Society B, showed that oxytocin levels jumped almost exactly as much in girls who were comforted in person as they did in girls who'd been calmed long distance.

The findings add to a growing body of research on the impact of oxytocin, which has been shown to promote such qualities as generosity and empathy.

Leslie Seltzer, the biological anthropologist who led the study, suggests an evolutionary reason for the soothing power of Mom's voice. When faced with a threat — say, members of a rival tribe — men could choose to fight or take flight, but women's options were complicated by having little ones in tow. Fleeing might expose the children to more danger. That's why, Seltzer speculates, women may have developed the ability to use social bonds to "tend and befriend" — to diminish stress either by touching or by talking. Seltzer's next study: to see if Mom can send some oxytocin love by instant message.

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