Why we use “baby talk”
We instinctively use high-pitched voices to talk to infants and pets. Is baby talk a silly affectation, or is there an explanation for this sing-song cadence?
How would you talk to an adult, a baby and a puppy? Most of us would adopt a different tone of voice for the latter two — slower, higher-pitched, exaggerated, musical.
Baby talk, or “parentese”, isn’t quite the same everywhere. Intonational exaggeration is more dramatic for speakers of American English compared to French, Italian, German, Japanese and British English. Regardless, you’d be hard-pressed to find a culture that doesn’t engage in baby talk to some extent. Even the Hadza people, who have no exposure to global media and speak a language unrelated to any other, use a high-pitched, rhythmic voice with babies.
In 2017, Elise Piazza and colleagues recorded mothers’ voices as they interacted with their infants and with other adults in their native language. Approximately half of the mothers spoke English and half did not. Analysis of the recordings indicated that the mothers’ voices shifted in similar ways regardless of language. A computer system was able to correctly identify speech as infant- or adult-directed 70% of the time.
Babies pick up on these timbre shifts too. In a large study, 67 labs across North America, Europe, Australia and Asia exposed infants to audio clips of mothers speaking either to their infants or to other adults. Interest in the audio clips was determined by eye tracking and observation of head movements.
Overall, the babies were more interested in baby talk. The preference was strongest when the baby talk was in their native language, but the babies also preferred baby talk in other languages over adult-directed speech.
The origin of baby talk
We can see some of the principles that underlie baby talk in other species. Both speech and song directed at babies are associated with “purer” vocal timbres, higher pitch and a more expanded vocal space. In non-human animals, these features often signal friendliness and approachability, while their opposites (i.e. low pitched, rough sounds) usually signal aggression. Contrast the way a cat sweetly meows at you with the way it growls and hisses at a rival feline.
We may have instinctively adopted these “friendly” vocal features to put infants at ease. But it’s also possible that some of these features have come to serve functions specific to our species. For example, an expanded vowel space makes speech clearer, which helps with language acquisition.
Pets love baby talk too
Of course, we don’t only use baby talk with actual babies. Many of us talk to pets, especially cats and dogs, in the same sickly sweet voices. Is there any benefit to doing so?
According to a study published earlier this month in Communications Biology, dogs really do prefer the same kinds of voices as infants. (Side note: If you’re looking for a canine equivalent to “parentese”, there’s some precedent for “doggerel”.)
Using functional magnetic resonance imaging (fMRI), Anna Gergely and colleagues identified two auditory regions in the brains of awake, unrestrained dogs that responded more to dog- and/or infant-directed speech than to adult-directed speech.
Higher average pitch and more variation in pitch were key factors in engaging the dogs’ attention, just as they are for babies.
Previous research has suggested that babies are more sensitive to baby talk coming from a female speaker than from a male speaker. Some scientists have suggested that babies develop this sensitivity following interuterine exposure to the voice of their mothers’ voices, or that babies are wired to pay more attention to adults who can feed them.
However, Gergley and colleagues’ study shows that dogs are more sensitive to female speakers’ baby talk too. Neither intrauterine exposure nor an ancient sensitivity to women’s voices suffices as an explanation here. Dogs’ — and perhaps infants’ —increased responsiveness to female voices may simply be attributable to the higher average pitch.
