Divergent developmental patterns for infants' perception of two nonnative consonant contrasts

Abstract Young infants discriminate nonnative and native consonant contrast, yet 10–12-month-olds discriminate most nonnative contrasts poorly, like adults. However, English-speaking adults and 6–14 month-old infants discriminate Zulu clicks, consistent with a model predicting that listeners who have a native phonology assimilate nonnative consonants to native categories when possible but hear non-assimilable (NA) consonants as nonspeech sounds (Best, McRoberts, & Sithole, 1988). Non-assimilable contrasts, thus, avoid language-specific effects and are discriminated, whereas consonants assimilated equally into a single category (SC) are discriminated poorly by listeners showing language-specific influences; other possible assimilation patterns show poor to excellent discrimination. This study directly compared discrimination of NA clicks and SC ejectives by 6–8- and 10–12-month-olds with a conditioned fixation habituation procedure. Consistent with predictions, the younger group discriminated both nonnative contrats and a control English contrast, whereas the older group discriminated only the NA and English contrasts.