Doctoral Dissertation: Language Interaction in Child Bilingual Speech: an Acoustic Study of Diphthongs

在学习第一语言的过程中，孩子们形成了一套特定于该语言的音素。同时学习两种语言需要习得两套音素。双语儿童是将这两套音素彼此分开，还是在语言发展的任何阶段，两种语言的音素会相互干扰？如果这两个系统之间存在相互作用，那么这种相互作用的本质是什么？它与成人双语者的相互作用有何不同？为了解决这些问题，目前的项目通过比较法英双语儿童与年龄匹配的两种语言单语儿童和成年法英双语儿童，来研究双语儿童的两种语音系统是如何相互作用的。本研究的重点是双元音的习得，双元音是一种复杂的元音片段，在文献中没有得到太多的关注。以往关于单音节元音产生的研究表明，双语儿童的语言互动影响，其语音特征重叠，与单语儿童的语音特征明显不同。本研究的结果将表明先前关于单元音习得的发现是否可以推广到双元音习得。此外，通过检查双元音的获取，该项目还解决了重要的方法问题，即如何通过使用平滑样条方差分析（smooth Spline ANOVA）来最好地捕捉复杂音段的动态特性，这是一种比较元音产生差异的相对较新的方法。这个项目将决定这种技术是否足以捕捉双元音的动态，以及它是否会产生比以前的技术更精确的结果。当前项目的结果将与双语儿童的父母以及与双语儿童合作的各种协会相关，这些协会可能对儿童双语习得的进展感到好奇。研究结果也可能与语言病理学等临床应用相关。鉴于双元音的语音复杂性，目前的研究可能会揭示它们通常比单元音更难习得。因此，儿童可能表现出涉及双元音产生的语言延迟。本研究的结果可能对临床医生构建双元音生成的基线数据有用。语言治疗师可能会参考这个基线，特别是在试图区分真正的临床语言问题和双语的潜在副产品时，后者可能被解释为语言障碍。

In the course of acquiring their first language, children develop a set of phonemes specific to that language. Learning two languages simultaneously requires the acquisition of two sets of phonemes. Do bilingual children keep these two sets of phonemes separate from each other, or do the phonemes of the two languages interfere with one another during any stages of language development? If there is interaction between the two systems, what is the nature of that interaction and how does it differ from that found in adult bilinguals? To address these questions, the current project examines how the two phonetic systems of bilingual children interact by comparing French-English bilingual children to age-matched monolingual children of both languages and adult French-English bilinguals. The study focuses on the acquisition of diphthongs, which are complex vowel segments that have not received much attention in the literature. Previous studies on the production of monophthong vowels have shown effects of language interaction in bilingual children, as evidenced by overlapping phonetic properties, which were significantly different from what was found for monolingual speakers. The results of this study will indicate whether the previously established findings on the acquisition of monophthong vowels can be generalized to that of the diphthongs. Additionally, by examining the acquisition of diphthongs, this project also addresses significant methodological issues on how to best capture the dynamic properties of complex segments by using the Smoothing Spline ANOVA, which is a relatively novel method for comparing differences in vowel production. This project will determine whether or not this technique is adequate for capturing diphthongs' dynamicity and whether or not it will produce more precise results than previous techniques. The results of the current project will be relevant to parents of bilingual children, and to various associations working with bilingual children that may be curious about the progression of children's dual language acquisition. The results may also be relevant to clinical applications such as speech-language pathology. Given the phonetic complexity of diphthongs, the current study may reveal that they are generally more difficult to acquire than monophthong vowels. Thus, children may show speech delays involving the production of diphthongs. The results of the current study may become useful to clinicians for the construction of baseline data regarding the production of diphthongs. Speech therapists may then refer to this baseline, particularly when trying to differentiate between real clinical speech problems and potential byproducts of bilingualism, which may otherwise be interpreted as speech impairment.