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Does Mom know you like the back of her hand? A new study says she once knew the back of your hand so well she could probably identify you by how it felt.

Researchers who blindfolded mothers and had them stroke the backs of three newborns' hands found that 70 percent could identify their own child if they had previously spent at least an hour with the baby since birth.That is far better than the 33 percent one would expect by random guessing, researchers said.

The women had apparently learned identifying features of their babies' skin during routine contact, because they were not allowed to study their babies specifically to prepare for the experiment, said study co-author Marsha Kaitz.

Kaitz, a psychology professor at Hebrew University in Jerusalem, presents the work in the January issue of the journal Developmental Psychology with co-authors at the university and the Shaare Zedek Medical Center in Jerusalem.

"It's pretty amazing, it's pretty exciting," said Tiffany Field, director of the Touch Research Institute at the University of Miami School of Medicine.

Dr. Michael Yogman, an assistant clinical professor of pediatrics at Harvard Medical School, called the study "a pretty impressive piece of work."

But he said he suspected the mothers were using other sensory cues, such as hearing the babies' breathing patterns, because he doubted that touch alone would produce enough information for identification.

Kaitz said the mothers could not have heard the breathing because they were at arm's length from the babies in a noisy nursery. She also said a separate experiment found that mothers could not identify their babies if the infants' hands were covered with cloth, showing that non-touch cues were insufficient.

Alan Fogel, a University of Utah psychologist who studies mother-infant communication, said he considered it quite plausible that a mother could get enough information from the touching to choose correctly at least most of the time.

Most participating mothers said they used the texture or temperature of the infant's hand.

"We were very surprised" by the results, Kaitz said in a telephone interview. "The women themselves are surprised."

It is not clear exactly which skin characteristics are responsible, she said, and mothers may learn them unconsciously.

The first of two experiments included 46 women, tested five to 79 hours after they gave birth in a large urban hospital. All the women breast fed their infants during daily visitation periods totaling 8.5 hours a day. Once women were told about the research and they agreed to participate, they did not see their children again until after the experiment.

Each participant's eyes and nose were covered with a heavy cotton scarf to block sight and smell. Each mother was tested with her own infant plus two others of the same sex and no more than six hours' difference in age. The babies slept face-down with the right hand lying flat on the mattress.

An experimenter placed the mother's fingertips on the back of each infant's hand, and the mother stroked gently for five to 10 seconds. Mothers were not allowed to touch the fingers or the edges of the hand.