Researchers at the RIKEN Brain Research Center in Japan have discovered the most effective method to soothe a crying baby, NewScientist reports citing Current Biology. Their discovery was led by work on the study of the so-called "transport reaction" in other mammals: it is known that in newborn cubs of animals, the heartbeat slows down when their mothers carry them in their arms.
To test this effect in humans, the team conducted an experiment involving 21 crying babies whose mothers tried to soothe them in four different ways: holding the baby in her arms while walking; rock it in a stroller or crib; keep on your knees; put into bed.
Babies did not want to calm down when their mothers held them in their arms while sitting or laid them in the crib. But when they were walked with them, all the children stopped crying, and almost half of them fell asleep within 5 minutes. Sickness in a wheelchair or crib had a similar calming effect, but to a lesser degree. This was probably due to the fact that the rhythmic movement during rocking has the effect of walking. Heart monitors attached to the babies showed that, like other mammalian babies, their heart rate slowed down when their mother carried them in her arms.
Scientists believe that the "transport response" evolved so that babies could sleep on their caregivers while they go about their daily business or try to escape with a child from a predator.
The researchers advise parents to hold their baby for another 5 to 8 minutes after they fall asleep before putting them to bed: the babies in the study tended to wake up if they were moved earlier.