Date of Award


Degree Name

Master of Arts


Teaching English to Speakers of Other Languages

First Advisor

Lakshmanan, Usha


This thesis is based upon a longitudinal study of L1 attrition in two bilingual teenage siblings, J and her older brother S, with Korean as their L1 and English as their L2. The two teenagers' initial exposure to English occurred at the age of 9. When the two siblings began to have sustained exposure to and immersion in an English L2 environment, they were at the postpubertal age. They had been attending high school in a Mid-Western city in the U.S for about two years when the study was conducted. The longitudinal study addressed three main questions. The first question concerned the siblings' language (L1 and L2) development, language dominance and cross-lingusitic influence from a bidrectional perspective. The second question examined the evidence for L1 attrition in relation to lexis, morphology and syntax, and their relative levels of vulnerability. The third question examined the role of extra-linguistic factors in the process of L1 attrition. In order to address the above questions, the two siblings were observed in their home over a period of 8 months. The data for the longitudinal study included the siblings' (i) spontaneous speech interactions in the home (ii) oral narratives in the L1 and L2 and (iii) their responses to a language background questionnaire. The results showed that the two siblings' English L2 developed and improved over time, but that they continued to maintain their L1 (Korean) as their dominant language. The evidence from both siblings' L1 and L2 use supported bidirectional cross-linguistic influence (i.e. from the L1 onto the L2 and from the L2 onto the L1). L1 attrition occurred only minimally in relation to morphology (e.g. honorification, case particles, classifiers, and plural marking) and lexical choice, while the siblings' L1 syntax remained relatively stable over time. Overall, the siblings were largely successful in maintaining their L1. In part, this was because their L1 was already firmly established or entrenched, as their immersion in an L2 environment occurred only when they were older (around puberty). Furthermore, their frequent use of their L1 for social networking, along with their positive attitudes toward their heritage language, also played a crucial role in maintaining and stabilizing their L1. Finally, the theoretical and practical implications of the findings of the present study, as well as recommendations for the future research are discussed.




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