The frustration many parents know all too well: you finally put your crying baby to sleep, put them in the crib… and the crying starts again. Science can have a trick on you.
Carrying a wailing baby for about five minutes, then sitting for at least another five to eight minutes can calm and lull the baby to sleep, long enough to allow the parent to put the child down without waking them, researchers report Sept. 13. Current Biology.
Some of the same researchers have previously shown that carrying a crying baby soothes the child and slows the heart rate (SN: 4/18/13). For the new study, the team is looking at what it takes to get a crying baby to nod off and sleep.
The researchers put heart rate monitors on 21 crying babies, ranging in age from newborns to seven months old. The team also recorded videos of the babies, watching their behavior as their mothers carried them around the room, sat holding them and placed them in the crib. That allowed the team to observe how the babies responded to different environments, whether they were crying, nervous, alert or drowsy.
“We’ve tested the physiology behind these which tend to be known, although it’s not well understood why they work,” says Gianluca Esposito, a developmental psychologist at the University of Trento in Italy.
The babies’ heart rates slowed and they stopped crying when their mothers picked them up and carried them around for five minutes. Even the babies fell asleep. But the researchers also noticed that the babies responded to the parent’s movement, whether they were in a deep sleep or not. For example, the baby’s heart was revived if the parent quickly turned around while walking or tried to get the baby down.
Sitting seems to be a smooth transition from walking to bed, observed by the team. Babies placed on mom’s lap in a crib tended to have a slower heart rate for at least five minutes and stayed asleep once in their crib. In contrast, the heart rates of the six children whose mother sat with them accelerated for less than five minutes once they were lying down and woke up soon after.
There is a lot of research on the relationship between babies and mothers, “but I haven’t seen work showing that babies respond to mothers’ behavior while the babies are sleeping,” says Sara Berger, a developmental psychologist at the College of Staten Island in New York, who was not part of the study.
Both Berger and Esposito caution that this method is not magic for all babies. It won’t rule out sleepless nights, but it’s still something parents can try, Esposito says. And while this study has been done with mothers, any child can do it comfortably. “Especially very, very young kids … as long as the kid’s caregivers are familiar, he’s going to do it,” he said.
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