School of Communication at Northwestern University :: Communication Sciences and Disorders

Infant sensitivity to distributional information can affect phonetic discrimination

Statistical cues facilitate infants' discrimination of difficult phonetic contrasts

Maye, Jessica, Janet Werker, & LouAnn Gerken (2002). Infant sensitivity to distributional information can affect phonetic discrimination. Cognition, 82 (3), B101-B111.

For nearly two decades it has been known that infants' perception of speech sounds is affected by native language input during the first year of life. However, definitive evidence of a mechanism to explain these developmental changes in speech perception has remained elusive. The present study provides the first evidence for such a mechanism, showing that the statistical distribution of phonetic variation in the speech signal influences whether 6- and 8-month-old infants discriminate a pair of speech sounds. We familiarized infants with speech sounds from a phonetic continuum, exhibiting either a bimodal or unimodal frequency distribution. During the test phase, only infants in the bimodal condition discriminated tokens from the endpoints of the continuum. These results demonstrate that infants are sensitive to the statistical distribution of speech sounds in the input language, and that this sensitivity influences speech perception.

Maye, Jessica, & Daniel Weiss (2003). Statistical cues facilitate infants' discrimination of difficult phonetic contrasts. Proceedings of the 27th Annual Boston University Conference on Language Development.

Certain phonetic contrasts are difficult for infants to discriminate, although they are easily discriminated by adults in whose languages those contrasts are phonemic. We argue that statistical cues in the input drive this facilitation of difficult contrasts; in addition, we investigate the nature of the representations formed on the basis of such learning. We tested 8-month-olds' discrimination of a contrast reported to be difficult for infants: prevoiced vs. unvoiced stop consonants. Our results show that prior to familiarization infants do not discriminate this contrast, but following exposure to a bimodal distribution of these sounds, the contrast is discriminated. In addition, familiarization to a contrast at one place of articulation facilitates discrimination at a different place of articulation, suggesting that learning occurs at the level of the phonetic feature.