The role of age, attitude and use for first language development and attrition in Turkish-English bilinguals

Recent decades have seen an increase in research informing our understanding of the complex way in which bilingual development is shaped by biological, cognitive and behavioral factors. We investigate the predictors that shape, drive and constrain the development of the L1 of bilinguals. We investigate 92 Turkish-English bilingual adults with a wide age at onset (AaO) range (0–42). We test their productive command of L1 lexical, morphological and syntactic features and investigate to what extent background variables relating to AaO, experience and attitudes are predictive of the relative level of proficiency across these features. In order to obtain a comprehensive picture of the interaction of these various linguistic and extralinguistic factors we employ structural equation modeling. We show that for speakers with younger AaOs, factors related to exposure are strongly associated with the level of L1 proficiency they retain as adults, while for later bilinguals, exposure-related factors matter less.