Babies learn power of voice through experimentation

ITHACA, N.Y. – A new study from Cornell University shows babies learn that their prelinguistic vocalizations – coos, grunts and vowel sounds – change the behaviors of other people, a key building block of communication.

The study is one of the first to propose that human development is driven by babies making predictions about the social world and is the first demonstration of vocal learning in prelinguistic infants over the first five months of life.

In contrast to the traditional view that babbling is only a byproduct of motor practice, the research found social responses to babbling facilitate infants’ active learning of the sounds they need to produce to effectively communicate.

When babies are three- to five-months old, they gain this knowledge by experimenting with adult responses, the researchers learned. A caregiver’s responsiveness to their infant’s vocalization is linked to the infant’s developing expectation that their vocalizations have social effects on strangers.

“A baby’s babbling functions as a tool, to probe the social world and figure out who to pay attention to,” said corresponding author Michael Goldstein, professor of psychology. “Babies don’t have unlimited energy or attention; a great strategy is to throw immature behaviors out there and see what comes back.”

In a study of infants and their caregivers at Cornell’s Behavior Analysis of Beginning Years Laboratory (B.A.B.Y. Lab), the researchers watched 2-month-olds and 5-month-olds play with their caregivers and an experimenter. After a minute of face-to-face play, the experimenter stopped responding to the infant, instead giving a neutral “still face” for two minutes.

The 2-month-olds showed no change in babbling. But the 5-month-olds responded strongly, with a burst of intense babbling, followed by a cessation of babbling. This reaction, called a “vocal extinction burst,” is something adults do all the time, Goldstein said.

“When the elevator doesn’t show up when you think it should, you’re likely to press the button more, or to press other buttons, he said. “You’re frustrated because your prediction wasn’t fulfilled, so your exploratory behavior increases – you do more stuff.”

The findings are important not just for parents of infants, but for anyone interested in communication, said lead author and doctoral candidate Steven Elmlinger.

Making predictions is a major job of the brain, Elmlinger said, and babies, as novice communicators, are beginning to form predictions that they themselves are successful communicators.

The study, “Learning how to Learn from Social Feedback: The Origins of Early Vocal Development,” published July 5 in Developmental Science.

For additional information, see this Cornell Chronicle story.

– 30 –