The Role of Linguistic Distance in First Language Attrition: A Comparison of Persian-English and Persian-Japanese Speakers

Abstract

First language attrition refers to the gradual decline or restructuring of a native language due to prolonged immersion in a second language environment. This thesis investigates how typological (dis)similarity between Persian (L1) and English/Japanese (L2) influences attrition across five grammatical features: pronoun, word order, formality, agreement, and yes/no question word. Using an acceptability judgement task and a background questionnaire with Persian-speaking immigrants, both structural outcomes and sociolinguistic moderators – age at immigration, length of L2 exposure, L2 proficiency, L1 contact, and attitudes – are analyzed. Results reveal that structural alignment between Persian and Japanese promotes L1 retention in some shared features, while English’s typological distance correlates with greater attrition. This study contributes to research on multilingualism by demonstrating how L2 structural properties and individual variation collectively shape L1 attrition or retention. In addition, it highlights the cultural and emotional significance of L1 maintenance in immigration communities, with broader implications for minority language preservation in L2 environments.