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Sensorimotor influences on speech perception in infancy
Edited by Patricia K. Kuhl, University of Washington, Seattle, WA, and approved September 10, 2015 (received for review May 2, 2015)

Significance
Theories of language acquisition have typically assumed infants’ early perceptual capabilities influence the development of speech production. Here we show that the sensorimotor (production) system can also influence speech perception: Before infants are able to speak, their articulatory configurations affect the way they perceive speech, suggesting that the speech production system shapes speech perception from early in life. These findings implicate oral–motor movements as more significant to speech perception development and language acquisition than current theories would assume and point to the need for more research on the impact that restricted oral–motor movements may have on the development of speech and language, both in clinical populations and in typically developing infants.
Abstract
The influence of speech production on speech perception is well established in adults. However, because adults have a long history of both perceiving and producing speech, the extent to which the perception–production linkage is due to experience is unknown. We addressed this issue by asking whether articulatory configurations can influence infants’ speech perception performance. To eliminate influences from specific linguistic experience, we studied preverbal, 6-mo-old infants and tested the discrimination of a nonnative, and hence never-before-experienced, speech sound distinction. In three experimental studies, we used teething toys to control the position and movement of the tongue tip while the infants listened to the speech sounds. Using ultrasound imaging technology, we verified that the teething toys consistently and effectively constrained the movement and positioning of infants’ tongues. With a looking-time procedure, we found that temporarily restraining infants’ articulators impeded their discrimination of a nonnative consonant contrast but only when the relevant articulator was selectively restrained to prevent the movements associated with producing those sounds. Our results provide striking evidence that even before infants speak their first words and without specific listening experience, sensorimotor information from the articulators influences speech perception. These results transform theories of speech perception by suggesting that even at the initial stages of development, oral–motor movements influence speech sound discrimination. Moreover, an experimentally induced “impairment” in articulator movement can compromise speech perception performance, raising the question of whether long-term oral–motor impairments may impact perceptual development.
Footnotes
- ↵1To whom correspondence should be addressed. Email: agreuel{at}audiospeech.ubc.ca.
Author contributions: A.G.B., D.K.D., P.K., and J.F.W. designed research; A.G.B. and D.K.D. performed research; A.G.B., D.K.D., P.K., and J.F.W. analyzed data; and A.G.B., D.K.D., P.K., and J.F.W. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1508631112/-/DCSupplemental.
Freely available online through the PNAS open access option.