The sounds babies make during their first year of life may be less random than previously thought, according to a language development researcher at the University of Texas at Dallas.
Dr. Pumpki Lei Su, an assistant professor of speech, language, and hearing in the School of Behavioral and Brain Sciences, is co-senior author of two recent papers in which researchers examined the sounds that infants make. The results suggest that children in their first year are more active in acquiring speech than previously thought.
“In these studies, we found that infants’ vocalizations did not occur randomly, but rather formed a pattern that produced three categories of sounds in groups,” said Su, who also directs the Children’s Language Acquisition and Interaction Lab (LILAC Lab) at the Callier Center for Communication Disorders. “The home recordings we analyzed included moments when adults were interacting with their children and moments when the children were alone, showing that children explore their vocal abilities with or without adult language intervention.”
A study, published on May 29 in Plus one, focused on babies with typical development, and the other, published on February 25 in the journal Journal of autism and developmental disorders, Focusing on infants who later received a confirmed diagnosis of autism, the researchers documented how children “play” vocally, learning which actions produce certain sounds and then repeating that process.
Over the past 40 to 50 years, scientists have realized that the vocalizations preceding a child’s first word are significant precursors to speech and can be divided into sequential stages of cooing, vocal play and babbling. Su’s team studied a data set of daylong recordings of more than 300 children collected by the Marcus Autism Center, a subsidiary of Children’s Healthcare of Atlanta, and coded by senior author Dr. D. Kimbrough Oller’s team at the University of Memphis.
“Parents tell us that sometimes a baby cries or makes low-frequency sounds for a very long period, but it has never been studied empirically,” Su said. “With access to a huge data set of hundreds of children over the first 12 months of their lives, we set out to quantitatively document how babies explore and group patterns as they practice different categories of sounds.”
Sound types are characterized by pitch and wave frequency such as squeals, growls, or vowel sounds. Plus one The study used more than 15,000 recordings from 130 typically developing infants in the data set. The infants showed significant clustering patterns: 40% of the recordings showed significantly more squeals than expected by chance, and 39% showed clustered grunts. Clustering was common across all ages, with the highest rates occurring after 5 months of age.
“Of the 130 infants, 87% showed at least one age where their recordings showed significant clustering of squeals and at least one age with significant clustering of grunts,” Su said. “There was not a single infant who, when all available recordings were evaluated, showed neither a single squeal nor significant clustering of grunts.”
Su said the study represents the first large-scale empirical study investigating the non-random emergence of the three main sound types in infancy.
In it Journal of autism and developmental disorders In a paper published in the journal Neurology, Su and colleagues showed that this exploratory behavior also occurs during the first year in children who are later diagnosed with autism spectrum disorder.
“Whether or not a child is diagnosed with autism, he or she groups sounds into one vocal category at a time,” Su said. “While the possibility that some patterns may be mimetic cannot be ruled out, these are not simple imitations; they do this with and without a parent present, even in the first month of life. This process of learning to produce sounds is more endogenous, more spontaneous than previously thought.
“We tend to think of babies as passive recipients of information. And parents are certainly their best teachers. But at the same time, they do a lot of things on their own.”
Su has received a three-year grant from the National Institute on Deafness and Other Communication Disorders (NIDCD) to study parents’ use of “parentese” (baby talk) with their autistic children. Parentese is an exaggerated style of speech that often contains high-pitched, drawn-out words and sing-song language.
In the literature, native language is presented as an optimal type of stimulation for typically developing children, who tend to pay more attention and respond more to it than to normal language. It also helps children learn to segment words. But is it also ideal for autistic children?
“One hypothesis for why parent use works is that it encourages social interaction by being very lively,” Su said. “Autistic children have differences in social communication and responses to sensory input. Would they also find parent use engaging? Could it be too loud or extreme? This new grant will allow me to examine whether parent use facilitates word learning in autistic children compared to a more standard adult-led recording.”
Other researchers who contributed to both papers include co-lead author Dr. Hyunjoo Yoo of the University of Alabama; Dr. Edina Bene of the University of Memphis; Dr. Helen Long of Case Western Reserve University; and Dr. Gordon Ramsay of Emory University School of Medicine. Other Marcus Autism Center researchers contributed to the paper. Journal of autism and developmental disorders study.
The research was supported by grants from the NIDCD (R01DC015108) and the National Institute of Mental Health (P50MH100029), both components of the National Institutes of Health.