Babies babble in just the right way

From San Diego at the Society for Neuroscience meeting.

A baby’s adorable babbling brings smiles to parents and grandparents, but it’s also a topic of serious study for scientists examining how people develop their language skills (SN: 5/27/00, p. 344: http://www.sciencenews.org/20000527/bob1.asp). There’s a debate, for example, as to whether babbling is a precursor to language or just

random sounds produced as the infant learns how to move its mouth.

The discovery that babies babble out of the right side of their mouths is the latest evidence suggesting that the infantile sounds are more than noise, say Siobhan Holowka and Laura Ann Petitto of McGill University in Montreal. Babbling “is absolutely a linguistic phenomenon,” asserts Petitto.

Past studies of adults speaking have established that people generally open the right side of the mouth more than the left side when talking, whereas nonlinguistic tasks requiring mouth opening are symmetric or left-centered. Neuroscientists argue that this linguistic asymmetry occurs because the neural circuits controlling language reside in the brain’s left hemisphere, and each brain hemisphere usually operates the opposite side of the body.

The two researchers videotaped the babbling of six babies, 6 to 12 months old, who were learning English or French. The scientists then scored which side of the mouth was more open during each vocalization, be it a repetitive babble such as “ga, ga, ga” or a nonbabble sound such as a coo or a laugh. All six babies had greater right-mouth opening during babbling and greater left-mouth opening or symmetric opening for their nonbabbling sounds.

The left side of the brain controls baby babbling, much as it controls speaking in adults, Holowka and Petitto contend. “From this, we conclude babbling is the beginning of language capacity,” says Holowka. The researchers suggest that monitoring when a baby begins to babble may indicate whether that infant will have trouble acquiring language.

D. Kimbrough Oller of the University of Maine in Orono, a pyscholinguist and author of The Emergence of Speech Capacity (2000, Erlbaum), applauds the new study. He also speculates that right-mouth asymmetry occurs for certain vocalizations seen in even younger infants.

From the Nature Index

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