Despite the number of bilinguals and speakers of English and Mandarin worldwide, up till now there have been no investigations of stuttering in any of the Chinese languages, or in bilinguals who speak both English and Mandarin. Hence, it is not known whether stuttering behavior in Mandarin mimics that in English, or whether speech restructuring techniques such as Prolonged Speech produce the same fluency outcomes in Mandarin speakers as they do for English speakers.
Research into stuttering in bilinguals is available but far from adequate. Although the limited extant studies show that bilinguals who stutter (BWS) may stutter either the same or differently across languages, and that treatment effects in one language can automatically carry over to the other language, it is unclear whether these findings are influenced by factors such as language dominance or language structure. These issues need to be clarified because speech language pathologists (SLPs) who work with bilinguals often do not speak the dominant language of their clients. Thus, the language of assessment and treatment becomes an important clinical consideration.
The aim of this thesis was to investigate (a) whether the severity and type of stuttering was different in English and Mandarin in English-Mandarin bilingual adults, (b) whether this difference was influenced by language dominance, (c) whether stuttering reductions in English generalized to Mandarin following treatment in English only, and (d) whether treatment generalization was influenced by language dominance. To achieve these aims, a way of establishing the dominant language in bilinguals was a necessary first step.
The first part of this thesis reviews the disorder of stuttering and the treatment for adults who stutter, the differences between English and Chinese languages, and stuttering in bilinguals. Part Two of this thesis describes the development of a tool for determining language dominance in a multilingual Asian population such as that found in Singapore. This study reviews the complex issues involved in assessing language dominance. It presents the rationale for and description of a self-report classification tool for identifying the dominant language in English-Mandarin bilingual Singaporeans. The decision regarding language dominance was based on a predetermined set of criteria using self-report questionnaire data on language proficiency, frequency of language use, and domain of language use. The tool was administered to 168 English-Mandarin bilingual participants, and the self-report data were validated against the results of a discriminant analysis. The discriminant analysis revealed a reliable three-way classification into English-dominant, Mandarin-dominant, and balanced bilinguals. Scores on a single word receptive vocabulary test supported these dominance classifications.
Part Three of this thesis contains two studies investigating stuttering in BWS. The second study of this thesis examined the influence of language dominance on the manifestation of stuttering in English-Mandarin BWS. Results are presented for 30 English-Mandarin BWS who were divided according to their bilingual classification group: 15 English-dominant, four Mandarin-dominant, and 11 balanced bilinguals. All participants underwent comprehensive speech evaluations in both languages. The English-dominant and Mandarin-dominant BWS were found to exhibit greater stuttering in their less dominant language, whereas the balanced bilinguals evidenced similar levels of stuttering in both languages. An analysis of the types of stutter using the Lidcombe Behavioral Data Language showed no significant differences between English and Mandarin for all bilingual groups.
In the third study of this thesis, the influence of language dominance on the generalization of stuttering reductions from English to Mandarin was investigated. Results are provided for seven English-dominant, three Mandarin-dominant, and four balanced bilinguals who underwent a Smooth Speech intensive program in English only. A comparison of stuttering between their pretreatment scores and three posttreatment interval scores indicated that the degree of fluency transfer from the treated to the untreated language was disproportionate. English-dominant and Mandarin-dominant participants showed greater fluency improvement in their dominant language even if this language was not directly treated.
In the final chapter, Part Four, a hypothesis is provided to explain the findings of this thesis. A discussion of the limitations of the thesis and suggestions for future research are also presented. The chapter concludes with a summary of the main contributions that this thesis makes to the field of stuttering in bilinguals.