Researchers at the University of British Columbia (UBC) have found that babies need free tongue movement to decipher speech sounds, and the study is the first to discover a direct link between infants’ oral-motor movements and auditory speech perception.
As described in a study article published in the October 12, 2015 edition of the Proceedings of the National Academy of Sciences, teething toys were placed in the mouths of 6-month-old English-learning babies while they listened to speech sounds—two different Hindi “d” sounds that infants at this age can readily distinguish. The researchers report that when the teething toys restricted movements of the tip of the tongue, the babies were unable to distinguish between the two “d” sounds. But when their tongues were free to move, the babies were able to make the distinction.
According to lead author Alison Bruderer, a postdoctoral fellow in the School of Audiology and Speech Sciences at UBC, the findings call into question previous assumptions about speech and language development.
“Until now, research in speech perception development and language acquisition has primarily used the auditory experience as the driving factor,” Bruderer said. “Researchers should actually be looking at babies’ oral-motor movements as well.”
The authors emphasized that the study does not mean parents should take their babies’ soothers and teething toys away, but it does raise questions about how much “free tongue movement” time infants need for speech perception to develop normally. It also has implications for speech perception in infants with motor impairments of the mouth, such as cleft palate, tongue-tie, or paralysis. The authors also note that their study indicates that moving their tongues and other articulators when they listen to speech may be an important factor in babies’ perception of the sounds.
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