Texas Tech University Health Sciences Center, Lubbock, USA.
J Speech Lang Hear Res. 2012 Oct;55(5):1449-62. doi: 10.1044/1092-4388(2012/11-0150). Epub 2012 Mar 12.
A previous investigation (Lee & Iverson, 2012) found that English and Korean stop categories were fully distinguished by Korean-English bilingual children at 10 years of age but not at 5 years of age. The present study examined vowels produced by Korean-English bilingual children of these same ages to determine whether and when bilinguals establish distinct vowel categories across their 2 languages.
Both English and Korean vowels produced by 40 Korean-English bilingual children (5 and 10 years of age) were examined in terms of 1st formant frequency (F1) and 2nd formant frequency (F2), vowel duration, and F1 and F2 formant trajectories.
Formant frequencies of vowels produced by the bilingual children were similar to those of monolingual English and Korean children. The bilinguals distinguished vowel categories across languages using both the assimilation and dissimilation mechanisms as identified by Flege, Schirru, and MacKay (2003).
Vowel categories developed earlier than stops in bilingual children because vowels were typically acquired earlier than consonants. The results of this study suggest that detailed phonetic categories do not form across the board and that bilingual children may invoke multidimensional representations of phonetic categories.
之前的一项研究（Lee & Iverson，2012）发现，英语和韩语的停止类别在 10 岁时被韩语-英语双语儿童完全区分，但在 5 岁时却无法区分。本研究通过检查相同年龄的韩语-英语双语儿童的元音，以确定双语者是否以及何时在他们的 2 种语言中建立了不同的元音类别。
本研究通过检查 40 名韩语-英语双语儿童（5 岁和 10 岁）的英语和韩语元音的第一共振峰频率（F1）和第二共振峰频率（F2）、元音时长以及 F1 和 F2 共振峰轨迹，来检验元音。
双语儿童所发元音的共振频率与单语英语和韩语儿童的共振频率相似。双语者使用 Flege、Schirru 和 MacKay（2003）确定的同化和异化机制来区分语言之间的元音类别。
在双语儿童中，元音类别比停止类别更早发展，因为元音通常比辅音更早习得。本研究的结果表明，详细的语音类别并非普遍形成，双语儿童可能会调用语音类别的多维表示。
