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

在习得第一语言的过程中，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。在语言发展的任何阶段，双语儿童是将这两组音素分开，还是两种语言的音素相互干扰？如果这两个系统之间存在交互作用，那么这种交互作用的性质是什么，它与成年双语者的交互作用有什么不同？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的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，这是一种复杂的元音片段，在文献中并没有得到太多的关注。以往关于单元音产生的研究表明，双语儿童存在语言交互作用，表现为语音特性的重叠，这与单语者的语音特性显著不同。这项研究的结果将表明，以前关于单元音习得的研究结果是否可以推广到双元音的习得。此外，通过研究双元音的获取，本项目还解决了如何通过使用平滑样条方差来最好地捕捉复杂音段的动态属性的重要方法学问题，这是一种比较元音发音差异的相对新颖的方法。这个项目将确定这项技术是否足以捕捉双元音的动态，以及它是否会比以前的技术产生更准确的结果。目前项目的结果将与双语儿童的父母有关，也与从事双语儿童工作的各种协会有关，这些协会可能对儿童双语习得的进展感到好奇。这一结果也可能与语音-语言病理学等临床应用相关。考虑到双元音的语音复杂性，目前的研究可能会发现，它们通常比单元音更难习得。因此，儿童可能会表现出与双元音的产生有关的言语延迟。目前的研究结果可能对临床医生建立有关双元音产生的基线数据有用。然后，言语治疗师可能会参考这一基线，特别是在试图区分真正的临床言语问题和双语的潜在副产品时，否则可能被解释为言语障碍。

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.