How to get a crying baby to sleep, according to science
A frustration many parents know all too well: you’ve finally rocked your crying baby to sleep, so put him in his crib… and the whining starts all over again. Science might have a trick for you.
Carrying a crying infant for about five minutes and then sitting for at least another five to eight minutes can soothe and lull the baby to sleep long enough for a 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 calms the child and calms a racing heartbeat (SN: 4/18/13). For the new study, the team looked at what it takes for the crying baby to nod off and stay asleep.
Researchers attached heart rate monitors to 21 crying babies, ranging in age from newborn to 7 months. The team also took videos of the infants and monitored their mood as their mothers carried them across a room, sat and held them and placed them in a cot. This allowed the team to observe how the babies reacted to different environments, whether they were crying, restless, alert or sleepy, heartbeat by heartbeat.
“We tested the physiology behind these things, which are well known, although why they work is not really understood,” says Gianluca Esposito, a developmental psychologist at the University of Trento in Italy.
The babies’ heart rates slowed and they stopped crying as their mothers picked them up and carried them around for five minutes. Some babies even fell asleep. But the researchers also noted that the babies tended to respond to their parents’ movement whether they were in deep sleep or not. For example, a baby’s heart rate accelerated when a parent turned quickly while walking or tried to put the baby down.
Sitting seems to facilitate this transition from going to bed, the team observed. Babies who were cradled on mom’s lap for at least five minutes tended to adjust to a slower heartbeat and continued to sleep once placed in their crib. In contrast, six babies whose mothers sat with them for less than five minutes once they were laid down had their heart rates accelerate and they woke up soon after.
There’s a lot of research on the relationship between infants and mothers, “but I hadn’t seen any work showing that infants respond to mother’s behavior while infants are asleep,” says Sarah Berger, a developmental psychologist at the College of Staten Island in New York who did not participate in the study.
Both Berger and Esposito point out that this method isn’t a magic wand for all babies. It doesn’t rule out sleepless nights, but parents can still try, Esposito says. And although this study was conducted with mothers, anyone an infant is comfortable with can do it. “Especially for very, very young kids… as long as those caregivers are comfortable with the kid, it will work,” he says.