Linda Polka
School of Human Commun. Disord., McGill Univ., 1266 Pine Ave. West, Montreal, PQ H3G 1A8, Canada
Janet F. Werker
University of British Columbia, Vancouver, BC V6T 1Z4, Canada
There is considerable evidence for a reorganization in speech perception during infancy that reflects the influence of specific language experience. Infants of 6--8 months of age reliably discriminate certain non-native consonant contrasts that 10- to 12-month-olds fail to discriminate unless they have experience with those categories in their everyday language. This recent research also shows a decline in English infants' discrimination of two German vowel contrasts, /y--u/ and /Y--U/, but discrimination at 6--8 months was below levels that have been observed for non-native consonant contrasts. The present experiment further investigated the timing and nature of developmental changes in cross-language vowel perception. Discrimination of German /u--y/ and /y--u/ and English /i/--/a/ was examined in English-learning infants aged 4 and 6 months using a habituation procedure. The 4-month-old infants discriminated all three contrasts, whereas 6-month-olds failed to discriminate both German vowel contrasts. The results indicate that developmental changes in discrimination of phonetic contrasts occur earlier for vowels than for consonants. Evidence for age-related changes in the internal structure of vowel categories will also be discussed.