Bilingualism but not bidialectalism influences cognitive control among young adult Chinese–English bilinguals

This study investigates whether bilingualism and bidialectalism influence cognitive control, and whether the two variables interact. The study compared two matched groups differing in second language (L2) proficiency through the Flanker and Wisconsin Card Sorting Test (WCST). The two groups were further divided into four groups differing in dialect proficiency, so that the effects of L2 proficiency and dialect proficiency and the interactive effect were examined. A mixed analysis of variance (ANOVA) was applied to the Flanker task data, with the task condition as the within-subject variable and the participant group as the between-subject variable. Independent t-test and ANOVA analyses were used to compare the performance differences between groups on the WCST. The high L2 proficiency group performed better than the low L2 proficiency group both in the Flanker task and the WCST, reflecting better monitoring and shifting ability. L2 proficiency effect on cognitive control was significant. However, no dialect effect was observed, and no interaction effect was found. Further multiple regression results confirmed the role of L2 proficiency but not dialect proficiency. This is one of the first bilingual studies to incorporate both bilingualism and bidialectalism simultaneously. The current research provides robust evidence that bilingualism is related to the enhancement of cognitive control, but questions the effect of bidialectalism.