Behavioural and Electrophysiological Evidences for the Effect of Bilingualism on Speakers’ Cognitive Control Ability By

Bilingualism means more than speaking two languages, it also has cognitive consequences. Recently, the question whether or not bilingualism affects cognitive control abilities has raised fierce debates. In this thesis, the effect of bilingualism on executive control was tested in different domains. First, bilingual speakers showed enhanced attentional control abilities while performing non-verbal executive control tasks. This was evident in terms of their response distribution profiles, which showed less extreme distribution tails than those of monolinguals, suggesting less frequent lapses of attention. Second, bilingual speakers resolved intra-language lexical competition differently from monolingual speakers. Their response distribution profiles as well as their brain activities were differentially affected in a picture naming task that manipulated the level of lexical competition. These results were best explained by bilingual speakers having enhanced engagement of executive control while resolving lexical competition within a single language, even though this might not be reflected at behavioural level. Third, bilingual speakers demonstrated enhanced task shifting abilities at a latent factor level, while they did not differ from monolinguals with regard to inhibition and updating abilities. Results also suggested a more correlated network of executive control for bilingual speakers than for monolingual speakers. Therefore, this thesis has obtained converging evidence that bilingualism benefits executive control. Reasons for inconsistencies in the literature and absence of the bilingualism effects are discussed.