How to put crying babies to sleep in 13 minutes

Japanese researchers have devised an up-to-the-minute guide to calming crying babies. Parents should carry their crying child close to their own body for about five minutes at a steady pace, if possible without abrupt movements, reports the team in the respected journal Current Biology. As soon as it falls asleep, they should sit with it for about eight minutes and only then put it down to sleep.

"Many parents suffer from their babies crying at night," says lead author Kumi Kuroda of the Riken Center for Brain Science (CBS) in Wako. "It's a huge problem, especially for inexperienced parents, that can lead to parental distress and, in a few cases, even infant abuse."

Kuroda's scientists developed the 13-minute concept in test runs with 21 infants under four conditions: the children were kept walking or sitting and placed in an unmoved or rocking bed - such as a stroller that was moved back and forth. The reactions were recorded, and the babies' heartbeats were recorded via an EKG.

Crying infants calmed down in about 30 seconds and their heart rate slowed when the mother walked while carrying them. All babies stopped crying, almost half of them fell asleep. If the mothers then tried to put their sleeping babies to bed, more than a third of the children woke up within 20 seconds. If they slept a few minutes before being laid down, they were noticeably less likely to wake up.

There was a similarly good calming effect with the rocking bed or stroller. It was far less effective when the mother held the baby in a sitting position or placed it in an unmoved crib. The heart rate of the babies then even increased. This was also the case when the mothers turned or stopped abruptly while walking with their baby.

Another finding of the team: walking for several minutes only helps sleep when babies are crying. "Surprisingly, this effect was absent when babies were already quiet," Kuroda said. Although only mothers were involved in the experiment, the researchers assume that the effect should be similar for all caregivers.

They also have an explanation for the calming effect of walking: the so-called transport reaction. This innate effect can be observed in many young mammals - such as mice and monkeys - that are not yet able to take care of themselves. The hatchlings will calm down and their heart rate will drop when picked up and carried around.

The scientists emphasize that the results of their small series of experiments would have to be confirmed in more specific experiments with larger samples. Then they want to use the findings for a business idea: a wearable device for babies that allows parents to see data like their child's heart rate in real time on their smartphones.