Abstract/Summary

Studies investigating the cognitive effect of bilingualism have yielded mixed results. Recently, interest has shifted to exploring the cognitive effects of speaking two varieties of one language (bidialectalism/diglossia) (Antoniou & Spanoudis, 2020). To explain the inconsistences, Green and Abutalebi (2013) introduced the Adaptive Control Hypothesis (ACH), which highlights the role of contexts in modulating Executive Functions (EFs) differently. The role of dual language use has commonly been investigated in bilingual settings, but rarely in bidialectalism/diglossia. In diglossia, the two varieties are separated by context, making it an ideal case for testing the Single Language Context (SLC), as defined by the ACH. In the first paper, all available evidence on the effects of diglossia/bidialectalism on EFs is reviewed in relation to the ACH. The findings from this study encourage future studies investigating bilingualism to consider the role of context. In the second paper, Arabic diglossic and English monolingual young adults were compared on tasks covering EFs’ three main domains (Miyake, 2000): inhibition (Flanker and Stroop tasks), switching (Colour– shape task), and updating (Nback task). The results revealed a diglossic disadvantage in Flanker and no diglossic advantages in the other tasks. Considering that advantages in young adults have been rarely reported (Bialystok, Martin, & Viswanathan, 2005), and due to the lack of a bilingual group to compare the ACH’s predictions in different contexts, in the third paper three groups of older adults were compared: Arabic–diglossics, bilinguals, and English monolinguals using the same tasks. The results revealed a diglossic advantage in Flanker when compared to bilinguals and a diglossic advantage in Stroop when compared to monolinguals. However, no advantages were found for the bilingual group. The results are discussed in terms of conversational contexts, and the related control processes.