L1-L2 interactions of vowel systems in young bilingual Mandarin-English children

•Young sequential bilingual children show bi-directional L1-L2 interactions.•Both midpoint formant values and vowel dynamic spectral change are affected by the L1-L2 interactions.•The L1-L2 interactions in young sequential bilingual children are mainly manifested in a form of assimilatory process.

This study examined the influence of L1 (Mandarin)-L2 (English) interactions on the organization of vowel systems and fine-grained spectral features of vowel productions in young bilingual Mandarin-English children. The participants included 39 children (15 bilinguals, 15 Mandarin monolinguals, and 9 English monolinguals) at 5-6 years of age. The bilingual children were divided into Bi-low (at the early stage of English learning with low proficiency in English) and Bi-high (highly proficient in English) groups. Each participant was recorded producing one set of Mandarin words containing /a, i, u, y, ɤ/ and/or one set of English words containing /i, ɪ, e, ɛ, æ, u, ʊ, o, ɑ, ʌ/. Formant frequencies at five temporal locations were measured. Both static (midpoint formant values) and dynamic (formant movement pattern, trajectory length) acoustic properties were examined. Bi-low children showed a strong effect of L1 on L2. The L1 features were maintained and transferred to the new phonetic system. Bi-high children produced L2 vowels in a near-native manner. Meanwhile, they tended to transfer some L2 features to their L1 and moved the L1 vowels closer to L2 vowels, which suggested an assimilatory process. Both static and dynamic spectral features were affected by L1-L2 interactions.