Effect of L2 phonetic learning on L1 vowels
This research examines the effect of L2 phonetic learning on L1 vowel production. Mandarin-English bilinguals differing in amount of L1 use produced Mandarin and English vowels. An acoustic analysis showed that both the Mandarin-English bilinguals of high L1 use and those of low L1 use deviated from the norm of Mandarin vowel /i/. The Mandarin-English bilinguals of low L1 use who successfully acquired English vowel /aj/ deviated from the norm of Mandarin vowel /aj/, indicating a carry-over effect of L2 vowel on L1 vowel production. In a perception test, Mandarin vowel production by the Mandarin-English bilinguals was presented to Mandarin as well as English listeners for goodness rating. The results showed that both Mandarin-English bilinguals of high L1 use and those of low L1 use differed significantly from Mandarin monolinguals in the production of /y/, a vowel with no counterpart in English. An analysis of inter-speaker variability indicated that some individual Mandarin-English bilinguals, including both speakers of high L1 use and low L1 use, were accented in the production of /y/, /aj/ and /aU/. Possible acoustic properties contributing to their accentedness included lower second formant frequency, larger first or second formant frequency movement, extremely short or long duration, and tone deviation. L2 English learning led to some Mandarin-English bilinguals carrying some English characteristics in their L1 Mandarin vowel production. In a follow-up perception test, the correlation between the ratings assigned to the Mandarin-English bilinguals’ production of Mandarin vowel /y/ and the ratings assigned to their production of English vowel /I/ and /E/ was examined. No inverse correlation was revealed, indicating that good L2 vowel production does not necessarily lead to poor L1 vowel production, and vice versa. This research suggests that the L1 phonetic system established in childhood does not remain static; instead, it may undergo reorganization when the L1 and L2 phonetic systems coexisting in a common phonological space interact.