A lullaby really can work magic. Science tells us why and how

It's after dinner. We've cleaned up the dishes and our youngest daughter is already asleep. My spouse has brewed tea and is queuing up something for the grown-ups to watch.

Standing (or rather lying) between me and sips of tea is my nearly 8-year-old. She's a little wound up from the school day. She tosses and turns, not quite ready to settle down.

In moments like this, I have a secret weapon: lullabies.

It's possible you're thinking: Of course an NPR reporter's secret weapon is Twinkle Twinkle. How very tote-bag.

I have two things to back me up here: heaps of anecdotal stories and actual scientific evidence.

First, an anecdote, in the form of a secret phone recording made in late April at around 9 p.m., as I climbed into the top bunk where my 8-year-old daughter sleeps.

"Do you want a song?" I ask Noa as she yawns.

"Yes, Sleep, Sleep, Sleepyhead," she requests. This is a favorite lullaby, we learned from taking Music Together classes for years when she was younger.

"OK," I say, and begin to sing, very very slowly. "Sleep, sleep, sleepyhead. Sleep, sleep, snuggle in your bed. I will keep you safe and warm so sleep, sleep, sleepyhead." You can hear my rendition — set against the hum of a white noise machine — in the recording below.

By the time I reach the end – 90 seconds later – she is snoring softly, and I slide out from under the covers and down the bunk bed ladder to enjoy my tea.

Honestly, when it works like this, it makes me feel like I have a superpower. Or I'm casting a spell: "You will fall asleeeeepppp. Listen to my voooiiice."

It's really not my superpower, though. It's the power of lullabies, especially when sung by parents and caregivers.

"If you think of a child's thoughts as racing and the mother or whoever comes in and sings slowly, rhythmically, it's going to slow their thoughts and then basically they're going to lull themselves into sleep," says Tiffany Field, a researcher on the faculty of pediatrics at the University of Miami School of Medicine.

She did a study of toddlers and preschoolers taking naps at the university nursery schools. The teachers played classical music at the beginning of naptime.

"With the toddlers there was a 35% faster sleep onset. With the preschoolers it was a 19% faster sleep onset, so of course the teachers loved that," she says.

Many of the studies on music and sleep are done with preterm infants in the NICU – including one which compared infants who heard Mozart to infants who heard their mother's lullabies plus a control group that didn't hear any music.

"What they found was that the mothers' lullabies were more soothing to the infants," she says. "They slept better, but they also showed a lot of the effects of decreased heart rate and respiration, better feeding, which probably explains why they had fewer days in the neonatal intensive care unit and their mothers' anxiety was reduced."

Now, I personally love to sing. But Fields says that is not a requirement for this to work. You can sing with any level of enthusiasm or skill, as long as it's slow tempo. If you really don't want to sing, a backrub can have similar effects, she says.

Still, there is just something about lullabies, says Sam Mehr, who studies the psychology of music at the University of Auckland. He also directs The Music Lab. His team did a study playing songs for infants in an unfamiliar language – some of the songs were lullabies, and some weren't.

The babies found all the songs pretty relaxing, he says, "but when they're listening to these lullabies, even though they're totally unfamiliar and not in a language the baby understands, they relax more. So there's something in the kind of DNA of lullaby that helps to calm infants."

He points out that doesn't explain everything, though. If a stranger came and started singing to your kid, it probably wouldn't have the same effect. He thinks the behaviors and actions involved when a parent sings to their child also may play a role.

"The fact that you're singing a lullaby when the baby's upset, you're not doing some other thing like that – the baby can tell that you're doing only that," he says. They can tell you're really paying attention to them and responding to their emotions in real time. Singing does seem to help older kids relax, too – as evidenced by my 8-year-old. But parents tend to sing more to babies than kids as they get older.

Mehr says the fact that babies respond especially well to lullabies brings up lots of ideas for future long-term research. "You can imagine that a parent who learns that this is the case and actually increases the amount of time that they spend [singing], you could imagine all these follow-on effects, where the baby's easier to soothe, so the parent's more chilled out and not as stressed about being a parent, which is already a pretty stressful thing," he says. Mehr says that reflects his own experience as a parent, but as a researcher he thinks that kind of long-term study would be hard to do.

There is some evidence that singing to infants can help boost a parent's confidence (that superhero feeling I get). One study of nearly 400 mothers in England found that singing to babies daily was associated with less postpartum depression and higher wellbeing and self-esteem. And in another study, mothers that sang to their children for 90 minutes in a group felt more closeness to their infants than mothers that talked and played but did not sing.

Of course, this is nothing new. Parents have been singing to their children for ages, all over the world. "Lullabies turn up a lot across cultures – they're just everywhere," says Mehr.

When Hirut Kassa is trying to get her 1-year-old son to sleep at home in Virginia, she keeps the lights low, rocks him and sings Eshururu, a song from her home country of Ethiopia.

She says it works like magic for both mother and child.

Your Turn: Do you have a favorite lullaby that you sing to your kids — or that you remember from childhood?

Email goatsandsoda@npr.org with the subject line "Favorite Lullaby" and share your story about a traditional lullaby from your childhood — or that you sing to your children. Record about a minute of the lullaby on your phone and share on the recording or in the email an explanation of where it's from and what it means to you. Include your full name and location. We may include your response in a story on npr.org. We are taking submissions until Tuesday, June 6.

"Sleepyhead" by Lyn Ransom. © 2002 Music Together LLC (ASCAP). Used by permission. www.musictogether.com

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