You know that goofy voice you use to talk to babies? Turns out it's actually a necessary part of their language-learning process. In a new study, researchers from Princeton uncovered a hitherto unknown part of mother-baby talk, or "motherese." The secret is timbre, or the unique quality of a voice—think of what makes Barry White or Daffy Duck sound so distinctive. The baby timbre is universal and exists in every single native tongue.
Timbre is the tone color or unique quality of our voice. We use it to distinguish human sounds from animal sounds, and, as this new study shows, we also use it to talk with babies.
Most people don't even know what timbre is, never mind how to change theirs, so it's likely that mothers aren't consciously changing their timbre to speak with their babies. But the fact that this feature exists in all mothers, regardless of their native tongue, means timbre could have an important part in human evolution.
For the study, published in Current Biology, the team recorded 12 English-speaking mothers as they played with and read to their infants, ages 7 months to a year. The team also recorded the mothers as they spoke with other adults. Then, using a voice-analysis computer program, the scientists measured the timbre in mother-child interactions and mother-adult interactions. The mothers showed a clear shift in timbre that couldn't be accounted for by pitch or background noises. When the researchers repeated this experiment in mothers speaking Spanish, Russian, Polish, Hungarian, German, French, Hebrew, Mandarin and Cantonese, the results were the same.
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"We were quite surprised that the timbre shift we found for English mothers exhibited such a consistent pattern across so many diverse languages," lead study researcher Elise Piazza, a neuroscientist at Princeton University, told Newsweek in an email. "These mothers were native speakers of one of these nine languages, and we asked them to speak only in that non-English language during all recordings."
The team still isn't quite sure why we change our timbre when speaking to children. They hypothesize that it may be a way for mothers to shift their children's attention to them from the time they are born, but this remains to be confirmed.
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Motherese is a long-acknowledged linguistic tool to help children learn language, but this study marks the first time that timbre has been recognized as playing a role in this sophisticated baby talk. Many questions remain, and the researchers only tested mother-to-child conversations, so they aren't sure if the same would be seen in father-child speech. However, Piazza suspects these results would be seen in fathers, and pretty much another else who communicates with a child.
"Adults are generally motivated to engage infants, and they intuitively know that babies respond well to the exaggerated patterns in baby talk," wrote Piazza. "Infant-directed speech is just one example of tailoring your communication style to a particular audience, which we do all the time."
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