Han, Xuran; (2022) An investigation of the effects of language experience on cognitive control in bilingual speakers. Doctoral thesis (Ph.D), UCL (University College London).

Focusing on Chinese-English bilinguals, this research project aims to explore the cognitive mechanisms underlying bilingual language processing and the effects of bilingual language experience on domain-general cognitive control in language comprehension and production processes through four behavioural studies. Specifically, it examines (1) how cognitive control adapts to dynamically-changing cognitive demands in language processing; (2) how bilinguals’ habitual language use patterns and contexts affect their development of domain-general cognitive control, through the convergence of linguistics and behavioural experiments approach. Study 1 explored how bilinguals’ habitual language experience affects their cued code-switching production and performance in cognitive shifting and inhibition tasks. Similarly, Study 2 also focused on understanding the effects of bilingual language use habits on cognitive shifting and inhibition; however, it investigated the relationship between bilinguals’ spontaneous language production and cognitive control. Studies 3 and 4 examine the adaptations of cognitive control in comprehending bilingual utterances in different interactional contexts. Specifically, Study 3 investigates how different language interactional contexts modulate domain-general inhibitory control in bilingual language comprehension. Study 4, consisting of two experiments, compares the effects of bilinguals’ code-switching habits and L2 proficiency on their inhibitory control during language comprehension in habitual and induced language use conditions. The results show that (1) cognitive control processes are adaptively deployed to produce and comprehend bilingual utterances in different interactional contexts; (2) bilinguals’ habitual language use patterns and language proficiency are significant factors modulating their domain-general cognitive inhibition and shifting efficiency; (3) the magnitude of bilingual language use experience effects on cognitive control vary significantly across processing languages in naturalistic and mandatory (i.e., induced) language use conditions. In general, the project addresses bilingualism being a dynamic process that includes multifarious individual differences that may affect cognitive control. Therefore, more comprehensive measures to characterise bilingual habitual language use experience are needed in future studies.