Most parents have experienced frustration when their children cry excessively and refuse to sleep. Scientists have found that the best strategy to calm them down is to hold them and walk with them for five minutes. This evidence-based calming strategy is presented in a paper published September 13 in the journal Current Biology.
“Many parents suffer from babies crying at night,” says corresponding author Kumi Kuroda of the RIKEN Center for Brain Science in Japan. “This is such a big issue, especially for inexperienced parents, that it can lead to parental stress and even child abuse in a small number of cases,” he says.
Kuroda and his colleagues have been studying the transport response, an innate reaction seen in many altricial mammals (those whose young are immature and unable to fend for themselves), such as mice, dogs, monkeys and humans They observed that when these animals hold their babies and begin to walk, their young’s bodies tend to become docile and their heart rates slow. Kuroda’s team wanted to compare the effects of the carry response, the relaxed reaction while being carried, with other conditions such as motionless maternal holding or rocking and also examine whether the effects persist with longer loading in human infants.
The researchers compared the responses of 21 infants in four conditions: being held by their walking mothers, held by their sitting mothers, lying in a still crib, or lying in a crib. The team found that when the mother walked while carrying the baby, the crying babies calmed down and their heart rates dropped within 30 seconds. A similar calming effect occurred when the infants were placed in a cradle, but not when the mother held the infant while sitting or placed the infant in a still cradle.
This suggests that holding an infant alone may be insufficient to soothe crying infants, contradicting the traditional assumption that maternal holding reduces infant distress. At the same time, the movement has calming effects, probably activating the baby’s transport response. The effect was most evident when the holding and walking movements continued for five minutes. All the crying babies in the study stopped crying and almost half of them fell asleep.
But when the mothers tried to put their sleeping babies to bed, more than a third of the participants became alert within 20 seconds. The team found that all the babies produced physiological responses, including changes in heart rate, that can wake them up the moment their bodies detach from their mothers. However, if the babies were asleep for a longer period before being put to bed, they were less likely to wake up during the process, the team found.
“Even as a mother of four, I was very surprised to see the result. I thought that the baby waking up during a snuggle is related to the way it is put to bed, such as its posture or the smoothness of the movement,” says Kuroda. “But our experiment did not support these general assumptions Although the experiment only involved mothers, Kuroda expects the effects to be similar in any caregiver.
Based on their findings, the team proposes a method to calm and promote sleep in crying babies. They recommend that parents pick up crying babies and walk with them for five minutes, followed by sitting and holding babies for another five to eight minutes before putting them to bed. The protocol, unlike other popular sleep training approaches such as letting babies cry themselves to sleep, aims to provide an immediate solution to babies’ crying. Whether it can improve infants’ sleep in the long term requires further research, Kuroda says.
“For many, we raise and intuitively listen to other people’s parenting advice without testing the methods with rigorous science. But we need science to understand a baby’s behaviors, because they are much more complex and diverse than what we thought,” says Kuroda.
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