Age-related effect on language control and executive control in bilingual and monolingual speakers: Behavioral and...

Research suggests that bilingual language control and executive control (EC) have similar mechanisms and share common brain networks. Managing two languages presumably reinforces these networks and enhances the level of general executive functioning in bilinguals. Despite a huge amount of research, there is not yet any consensus on the nature of the potential bilingual advantage. The overall purpose of the present research was thus to gain insights into the influence of bilingualism on executive functions, by exploring aging-related changes. The domain-general tasks approach consisted in comparing young and older bilinguals with their monolingual peers on tasks that were deliberately chosen to assess different aspects of inhibition (Stroop, Antisaccade, and Stop Signal tasks) and cognitive flexibility (Berg Card Sorting Test, Trail Making Test and verbal fluency). Our goal was to ascertain whether bilinguals outperform monolinguals, and whether this advantage is greater for older bilinguals. Results provided some evidence of a bilingual advantage in verbal tasks involving language processing, such as verbal fluency and the Stroop test, but did not support the hypothesis of a general executive advantage, as bilinguals and monolinguals did not differ on nonlinguistic executive tasks. The language switch task approach consisted in studying the performance of young and older bilinguals on picture naming while switching between their dominant and nondominant languages, and comparing their performance with monolingual speakers in an equivalent switching paradigm. The effects of aging on mixing and switch costs were investigating by analyzing behavioral and event-related potential (ERP) data. Results of these tasks did not reveal any effect of aging on mixing cost in bilinguals. Furthermore, ERP data pointed to a degree of flexibility in older bilinguals, who were able to allocate resources according to task difficulty. Taken together, our results suggest that a bilingual advantage is only observed in language-based tasks.