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When most of us see an infant, we shamelessly slip into baby talk: Whooose a prettee baabee? Such a cuutiee.
Our speech gets smoother, slower, higher pitched and sing-songy. Researchers call this altered form of speech “parentese,” but almost everybody does it — uncles, neighbors, even the nice lady at the grocery store.
Based on research going back decades, scientists have found that engaging infants in baby talk happens in all industrialized societies. But is it a universal human trait?
In a wide-ranging study, researchers at Harvard University’s Music Lab collected 1,615 speech and song recordings directed at infants — or, alternatively, adults — by 410 people in 21 diverse societies. They included urban, rural and remote, indigenous cultures.
The findings were published in July in the journal Nature Human Behavior.
“Most of the research looking at this have studied urban societies in the U.S., Canada, Germany, Sweden, Russia,” said Courtney Hilton, postdoctoral fellow and principal author of the study, who is now at Yale University’s Haskins Laboratories.
“But to make a rigorous claim that there is any kind of instinct to do this,” she said, “we have to study more diverse cultures.” So they studied people from rich, poor, urban, rural and isolated cultures on six continents, people speaking 18 different languages, from Southern California to East Africa and New Zealand to China.
What they found was that everyone altered speed, rhythm, volume and other vocal traits when they talked to infants, compared to the way they spoke to adults. When face to face with a baby, people spoke slowly, elongated vowels and used a sing-song rhythm.
The research team made recordings of people speaking and singing, to infants, then to adults.
“We used computer algorithms to sort out how rough is the voice, how high the pitch, and so on and then analyzed that,” said Cody Moser, a Ph.D. student in cognitive and information sciences at UC Merced and co-author of the study.
“A low pitch will go up higher when talking to an infant,” he said. “A lifelong smoker will have a rough timbre, but will try to smooth out their voice when talking to a baby.”
People can’t seem to stop themselves even when mocked for using “baby talk.”
“You or I would not be surprised to hear differences when we speak to infants compared to adults,” said Dorsa Amir of the psychology department at the University of California Berkeley.
She worked with the Harvard Music Lab’s researchers in the field in Ecuador. When the recordings were complete, she was delighted to share them with her research subjects — the Shuar people in the Ecuadorean Amazon, where recording devices are uncommon.
Theirs is a hunter/horticulture society, and when they heard themselves, they laughed with joy.
“I played back the recordings, and it was like a little concert,” Amir said. “They were so excited.”
They were excited … but notably not surprised by how they sounded.
They heard differences in their voices — in pitch, tone, rhythm — when they spoke to infants versus when they spoke to adults. And they seemed to expect to hear differences.
“I got the feeling they knew it would be different. That’s the cool part, that there’s this common thread in being human,” Amir said.
They knew, like most of us know, that how we speak to babies is different.
People in all the societies that were part of the study modified the roughness in their voices similarly. “From Toronto to hunter/gatherer people in Africa, everyone used a smoother sounding rather than harsh sounding voice,” Moser said.
But not every society marches in lockstep when confronted with a baby.
“The Shuar people pitched their voices higher, but not as exaggeratedly high as people in Western countries,” Moser said. “So there might be some cultural factors that shape voice changes as well.”
For example, in some remote indigenous cultures, mothers and fathers work constantly and don’t have as much time to focus solely on the baby, Amir said. They might speak more casually, as an aside while cooking or gardening, with fewer exaggerated changes.
The Mbendjele Bayaka people from the Republic of Congo don’t use infant-directed speech as often as people in industrialized parts of the world, Moser noted. In fact, in some smaller, remote societies, people hold off on speaking directly to children until they’re older.
In those cases, Amir said, most infant-directed speech to babies comes from older children, who weren’t part of the study. But the Mbendjele Bayaka people sing a lot of lullabies that, like other infant-directed speech, emphasize and elongate vowels, and are slower and higher pitched.
Everybody does it in one form or another. The the next question is, why? Why do people around the world speak differently when talking to babies?
Erik Thiessen, who was not associated with the Harvard Music Lab study, has been studying that at the Infant Language and Learning Lab at Carnegie Mellon University.
“First and foremost, what we know about infant-directed speech is that babies like it,” Theissen said. “They’re interested in it, and when you’re interested, you learn more easily.”
They know this, he said, from learning studies showing, for example, that when infants are interested in something, they’ll suck harder and longer on their pacifiers.
You might wonder, is baby talk teaching infants anything? Sure, the word “blankie” for blanket or “binkie” for pacficer isn’t helping build a viable adult vocabulary, but something is being transmitted: grammar!
Thiessen has found that parents are about as grammatically correct when talking to babies as they are when speaking to adults. And the way they’re speaking is likely helping babies learn language.
“Adults are hyper-articulating words, making speech clearer, for infants,” Thiessen said. And because of these speech modifications, such as drawing out the vowels in cuutee pie and separating the sounds with hard consonant sounds, he said, infants are probably beginning to figure out where one word ends and another begins — the foundation of lifelong speech.
Adjusting the way we speak can help babies learn something about emotions, too. The way adults speak to infants is one of the first tools that parents have to communicate that mom or dad is happy or not-so-happy.
“All languages have some similarities in how they convey emotions,” Thiessen said. “Bad is always short, loud, sharp sounds. Good is slower and lower and rhythmic and reassuring, almost like rocking the baby to sleep.”
The new study, Thiessen said, is a huge step forward in looking at infant-directed speech across diverse cultures. “This helps us be more confident in saying that infant-directed speech is fairly close to universal,” he said.
It’s amazing to think that there’s something all the world’s people seem to have in common.
“These commonalities are almost woven into our biology,” Hilton said. “From people in crowded urban centers in Beijing, all the way to a tiny hunter/gatherer society in South Africa, there is something we share.
“It’s a kind of instinct that ties people together. If you were to translate the takeaway from the new study into parentese, you might say slowly and in a sing-songy and high-pitched voice: Weee are soooo aliiiike.”
Guest writer Susan Brink is a freelance medical reporter based in Portland. A graduate of the Medill School of Journalism at Northwestern University, she is the author of two books on medical issues, “The Fourth Trimester: Understanding, Protecting and Nurturing an Infant Through the First Three Months,” and with Dr. Daniel Levy, “A Change of Heart: Unraveling the Mysteries of Cardiovascular Disease.” She has two daughters and six grandchildren. The story appearing here was first published by NPR.
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