Scientists Discover why Babies Stop Crying when Carried

Researchers have finally uncovered the actual mechanism that makes babies stop crying when they are picked up and carried for a while.

A team of researchers from the RIKEN Brain Science Institute in Japan found that a coordination of nervous, motor and cardiac regulations play an important role in the infant's calming response to carrying.

"From humans to mice, mammalian infants become calm and relaxed when they are carried by their mother," Kumi Kuroda of the RIKEN Brain Science Institute said in a news release. "This infant response reduces the maternal burden of carrying and is beneficial for both the mother and the infant."

To analyze the link, Kuroda and team conducted experiments both on human babies and mouse pups. ECG measurements showed that the heart rates of babies declined considerably after they were picked up and carried for a while.

The findings were later re-confirmed on mouse pups. "They appeared relaxed, but not totally floppy, and kept the limbs flexed. This calming response in mice appeared similar to me to soothing by maternal carrying in human babies," Kuroda explained.

The authors expect their findings to help parents provide better care to their babies and prevent child abuse.

"A scientific understanding of this infant response will save parents from misreading the restart of crying as the intention of the infant to control the parents, as some parenting theories-such as the 'cry it out' type of strategy-suggest," Kuroda said. "Rather, this phenomenon should be interpreted as a natural consequence of the infant sensorimotor systems."

The study has been reported April 18 in the Cell Press journal Current Biology.