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The science of baby talk

Mothers across the globe subconsciously change the tone of their voice when they talk to their baby to help them learn, a new study found.

Regardless of the language spoken, all mothers use a universal ‘motherese’ or ‘baby talk’ when they address to their infants, which is an exaggerated and somewhat musical form of speech.

While it may sound silly to adults, studies show it plays an important role in language learning, engaging infants’ emotions and highlighting the structure of language to help babies decode the puzzle of syllables and sentences.

Now Princeton University researchers have found another unique feature of the way mothers talk to their babies, claiming they shift the timbre of their voice in a specific way.

A new study from Princeton University has found that mothers adjust their timbre when addressing their newborns (file photo)

A mother shifts the timbre, which is defined as the quality of a sound, in her voice so her newborn can recognize and pay attention to her from birth, the researchers explained, adding that the same could be true for fathers.

For the study, researchers recorded mothers while they played with and read to their seven- to 12-month-old infants and when they spoke to another adult.

The differences in timbre they noticed were strong enough to be reliably picked out by a machine learning algorithm, and researchers said that the shifts suggested there was a universal form of communication with infants.

Researcher Elise Piazza said her team had discovered ‘a new cue that mothers implicitly use to support babies’ language learning’.


A separate study recently revealed that baby talk evolved as a way to make parents seem less intimidating to their children. 

The researchers studied the movements that mothers make with their lips and tongue while talking to their babies to decipher the origins of baby talk. 

When mothers speak to their babies, which is formally known as infant-directed speech, they unconsciously adjust their voice box to speak in a higher pitch.

The researchers suggest that our ancestors may have unconsciously raised their larynx to produce a squeaky voice that appears less aggressive to their offspring.

The timbre shift was consistent across women who spoke 10 languages: English, Cantonese, French, German, Hebrew, Hungarian, Mandarin, Polish, Russian and Spanish.

Professor Jenny Saffran who teaches psychology at the University of Wisconsin explained: ‘We’ve known for a long time that adults change the way they speak when they are addressing babies.

‘They speak more slowly, use shorter sentences, talk at a higher pitch and swoop their pitch up and down more often than when they are speaking to other adults.

‘This is the first study to ask whether mothers also change the timbre of their voice, manipulating the kinds of features that differentiate musical instruments from one another.’

Piazza said: ‘We found that mothers alter this basic quality of their voices when speaking to infants, and they do so in a highly consistent way across many diverse languages.’

The researchers suspect the unique timbre fingerprint mothers use when addressing newborns could help babies learn to differentiate and direct their attention to their mother’s voice as soon as they are born.

Piazza also said that the report could lead to new types of speech analysis.

Specifically, she said the findings could allow speech recognition technology to quickly identify the speech mode that mothers use when addressing their babies across all languages.

‘Our work also invites future explorations of how speakers adjust their timbre to accommodate a wide variety of audiences, such as political constituents, students and romantic partners.’

Future research will explore how the timbre shift helps infants learn. The study was published in the journal Current Biology.