Baby talk helps little ones learn to speak
Research indicates that speaking ‘motherese’ can help little ones learn language
All around the world, parents talk differently to babies than they do to adults. With their young kids, parents switch into a mode of communication known to linguists as “motherese” or infant-directed speech, and known more commonly as baby talk, a form of speech featuring long pauses and a roller-coaster of pitch changes.
For example, imagine the upward swing in pitch our voices take toward the end of a question (“Do you want to go to the park today?”): It’s much more dramatic when we address young children.
While parents may feel a bit silly using baby talk, they shouldn’t: Babies not only prefer listening to these exaggerated contours, but they also learn new words more easily from them. By highlighting the structure of speech, such as the differences between the vowels “A” and “O,” motherese helps babies translate a torrent of sound into meaningful language.
Although scientists know a lot about the changes in rhythm and pitch in infant-directed speech, we know much less about the role of timbre, or tone colour, which includes the breathiness, roughness or nasality in a voice.
The timbre of an instrument (whether buzzy, warm or twangy) affects how we experience music, but its role in language is less obvious. When my colleagues and I looked into the tone colour of baby talk, we made some surprising discoveries.
Mothers change their overall timbre when speaking to babies, like they’re morphing their voice into a different instrument to address these little listeners.
Though it’s a less well-understood property of sounds, we do know that timbre can provide an important pointer to different sound sources, thus helping us identify people, animals and objects based on their characteristic auditory “fingerprints.”
So, we wondered whether mothers might unconsciously change their overall fingerprints when talking to their babies, perhaps to signal that an important source of speech, which is highly relevant for learning, is coming their way. In a recent study published in Current Biology, we report that mothers shift their overall vocal timbre when speaking to their infants.
In the Princeton Baby Lab, where researchers study how children learn, we recorded English-speaking mothers while they played with and read to their seven- to 12-month-old babies, and while they spoke to an adult experimenter.
We then came up with a mathematical formula for the timbre fingerprint of each mother’s voice and found that adultdirected and infant-directed speech had consistently different fingerprints.
Specifically, we were able to train artificial-intelligence software to distinguish infantand adult-directed speech, even when we fed the software just one second of speech.
Most surprising, in a second sample of non-English-speaking mothers, we found this timbre shift was also highly consistent across nine languages (Spanish, French, Russian, Polish, Hungarian, German, Hebrew, Mandarin and Cantonese).
This suggests these timbre shifts may represent a universal form of communication with infants.
Being able to identify baby talk across multiple languages could give us rich information about the amount and type of language children hear at home and at preschool (for example, overheard adult conversation vs. speech directed at them) across different cultural environments. This could help researchers and educators predict and improve outcomes such as vocabulary and success in school.
Because the mothers in our study were never specifically told we were measuring the acoustical properties of their voices — they just knew we were broadly interested in their interactions with their babies — these shifts are highly natural and possibly unconscious. And given how well they generalized across the diverse group, it’s likely they’re an important cue used to capture babies’ attention and help them learn language.