Khatawut Chaemchamras/EyeEm/Getty Images
Khatawut Chaemchamras/EyeEm/Getty Images
You've heard it. You've probably done it. We're talking baby talk.
And it turns out, the features of baby talk — softer tone, higher pitch, almost unintelligible vocabulary — are global.
Researchers at Harvard's Music Lab documented over 1,500 recordings in 21 urban, rural and Indigenous communities — making their work possibly a first of its kind experiment.
Listen to baby talk in English
Listen to baby talk in Mandarin
Courtney Hilton, one of two lead authors on the research, told NPR's Michel Martin that the team wanted to get beyond Western cultures.
"For the case of these infant-directed vocalizations, people have studied this in Western and urban societies for many decades at this point," said Hilton, who's now at Yale University. "But we don't really know that much about how that varies across societies."
For the recordings, the team asked people to speak to their babies as if they were fussy. Researchers also recorded adults singing to the babies in a variety of languages and then repeating that process with another adult.
That includes the Nyang'atom people in eastern Africa:
Nyang'atom people singing to a baby
Nyang'atom people singing to an adult
More than 50,000 participants who judged if what they heard was adult speaking to adults — or adults talking to babies.
And as to whether all of this baby talk hurts language development, Hilton advises there are some theories that it actually helps infants.
"There really isn't much evidence that speaking in baby talk to babies [is] really harmful," he said, "at least up until a few years of age."
This interview has been edited and condensed for clarity.
On why humans do baby talk in the first place:
There are many reasons why this kind of baby talk might have evolved in humans and why it might serve beneficial purposes. Some theories suggest that the way we speak accentuates the vowels of the speech and helps babies learn speech.
Other theories suggest that this kind of baby talk helps regulate the baby's emotions and helps structure the social interactions we have with babies, so it helps socialize them and control their behavior and mood.
And of course, these things are all great for us now in modern societies, but say a million years ago in Pleistocene Africa, people living back then would have been in far harsher conditions, and the struggle for survival was a bit more acute. In those situations, having ways to interact with babies and to care for them while still being able to keep your eyes up to look out for predators and use your voice to interact with babies, that might have been an important reason why we may have evolved these kinds of behaviors.
On which recordings most fascinated him:
The Hadza people live a very different life than Western people, only interacting with a group of about 30 to 40 other people. And they have next to no exposure to global media via the Internet, radio and TV. And the Hadza language is also called a language isolate, meaning that it is not related to any other known living language.
Despite all these differences, we still hear in some of these recordings that people engage in the same sorts of vocalizations — raising the pitch of their voice and speaking in a more rhythmic way when they address infants.
Hadza people speaking to children
Hadza people speaking to adults
On how researchers thought of the idea for this study:
The genesis of this project came from the leader of our lab, Samuel Mehr, chatting with other people at a conference and just having the idea that we could work with some of these anthropologists that we have some relationships with — give them to microphones that they that they can take them to the field and make some recordings of infant directed speech and song.
Then that ballooned out into this larger project that we have today, where we ended up with about 40 different collaborators on this research project, many of which are anthropologists with expertise in many of these societies.
We did end up with 21 societies' worth of recordings — many of which include small-scale societies that are very different from Western societies in terms of how they live their lives.
On the importance of doing this research beyond Western societies:
The easy part about studying infant-directed speech is making recordings and analyzing them. The hard part is really doing this cross-culturally.
This is partly because cultures are spread geographically around the world, and then there are also all sorts of cultural and linguistic barriers.
This is why we collaborated with many anthropologists with on-the-ground expertise with many of these societies.
We need to go beyond just studying Western cultures. And for the case of these infant-directed vocalizations, people have studied this in Western and urban societies for many decades at this point.
But we don't really know that much about how that varies across societies. And being able to understand whether this is common across societies might give us clues as to whether this is something that has links to our basic biology as humans or whether this is something we are enculturated into through interacting with other people in our culture.