(Inside Science) -- Psychologist Seth Pollak hopes that you gave mom a call on Mother's Day -- not for her sake, but for yours. His new research suggests that, for daughters, a talk with mom can produce the same soothing hormone in the brain as a hug.
The hormone in question is oxytocin -- the "cuddle" or "love" hormone, released during physical contact with people we care about. It is thought to play a part in reinforcing the social ties that bind us. Pollak's study is the first to show that the hormone can be triggered not only by a soft touch but also by a kind word.
Oxytocin has been used as a drug to induce uterine contractions and child birth for decades, but only recently have scientists discovered the roles it plays in our everyday social lives. Our brains produce it when we pet a dog, and it also seems to help us remember the faces of those close to us. A small dose of oxytocin makes people playing games in psychological laboratories more trusting of each other, and pregnant women with increased levels tend to be more affectionate toward newborns.
In 2005, Pollak discovered that children raised in Romanian orphanages -- left neglected in cribs without physical contact -- do not make the same amount of oxytocin when touched by their adoptive mothers in the U.S. as well cared-for children do. This deficiency, he suspects, might explain why these children have trouble in relationships later in life.
That's because animal studies have shown that close physical contact between animals and their mates and close relatives can trigger the hormone. The dedicated and monogamous female prairie vole -- which bonds with its mate for life -- tends to be more likely to cheat on its partner with strangers when injected with an oxytocin-blocking chemical.
Pollak's latest study at the University of Wisconsin at Madison explored the role of words in shaping healthy bonds between mothers and daughters.
"We're asking an evolutionary question here," said Pollak, who published the research in the scientific journal Proceedings of the Royal Society B. "Is it possible that our evolution of language is connected to oxytocin?"
He stressed out 61 girls aged 7 - 12 by having them speak in front of a crowd and work math problems for a panel of judges. After this trying ordeal, some of the girls received a hug from their mothers and others received a phone call. Urine samples from both groups of girls showed a general drop in stress hormone levels and an increase in oxytocin.
Girls who enjoyed the afternoon watching the film "March of the Penguins", on the other hand, showed no change in hormone levels when contacted by mom.
Oxytocin is thought to act on the parasympathetic nervous system, to send feelings of safety that calm stress -- though exactly what parts in the brain and body oxytocin targets is still not completely understood.
"About 10 years ago, AT&T had this slogan 'reach out and touch someone'," said Pollak. "It turns out that when someone calls us who is close to us, neurobiologically it is having the same effect as them giving us a hug."
Whether a mom's voice could have this effect on her son, or a dad's voice on his children, remains unknown because male and females respond differently to the hormone.
Scott Young, who studies oxytocin at the National Institute of Mental Health in Bethesda, Md., said that the results make sense in light of previous studies, but cautioned that this study is the first to look for oxytocin triggered by the voice.
"This field is very new, all of this stuff with social behavior," said Young. "It would be nice to see some replications to confirm the experiments."