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Texting may be how tweens prefer to communicate, but when the chips are down, nothing soothes like Mom's voice.

Instant messaging may be one of the hottest ways for kids to communicate, but it doesn't hold a candle to hearing your Mom's voice when you're a stressed-out tween.

For young girls, the sounds of a mother's reassuring words over the telephone were as soothing as talking with her in person, finds a new study. Yet when researchers compared these reactions to daughters who had only a high-tech IM exchange with their Moms, they found the girl's stress levels were similar to those who had no contact with a parent at all.

"Hearing one another is still an important part of human communication," says Leslie Seltzer, a post-doctoral fellow in biological anthropology at the University of Wisconsin at Madison, and the study's lead author. (We link to an abstract of the study, above. If you'd like to read the whole thing, you'll need to purchase it.)

The study, which appears online in Evolution and Human Behavior, tracked 68 girls between the ages of seven-and-a-half and 12. All the girls completed a questionnaire about their mother-daughter relationships and were given a 15-minute task to test their math and verbal skills.

Afterward the girls were assigned to one of four groups: One saw and spoke with their mother for 15 minutes after the stressful task, a second had a phone conversation for the same amount of time, a third could instant message their Moms, and a fourth had no parental communication.

Participants had both their cortisol levels in their saliva, a measure of stress hormones, as well as their oxytocin levels in the urine, a hormone linked with mother-child bonding, tested frequently during the experiment. Scientists found that stress levels of the girls who had no parental interaction were similar to those who texted and were higher overall than girls who had direct or verbal contact with their mothers. And the girl's who texted did not release oxytocin, a response comparable to those having no parental contact.

"Instant messaging falls short of the mark when it comes to conveying a hormonal signal of comfort," explains Seltzer. "It makes sense that the hormones responsible for attachment and stress-buffering would respond to social vocalizations, which are several billion years old, as opposed to writing in any form, which is a very recent innovation," she adds.

Interestingly, the strength of the mother-daughter relationship didn't seem to influence communication. And while tweens may IM their peers for comfort, exchanging texts with Mom may be totally different. A daughter's stress levels could possibly climb if a parent is not as quick with the words or as adept with the technology as her friends.

Seltzer says she would be surprised if a generation who have grown up texting and IMing will have a different physiological response to their child's use of these technologies when they eventually become parents.

"That would represent an ability very unique to humans -- the ability to elicit a hormonal cascade in response to viewing symbols," Seltzer explains.

Moms, dads, and kids: When you need reassurance, what's most comforting -- texting, talking face to face or phone?

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