How language proficiency and age of acquisition affect executive control in bilinguals: continuous versus dichotomous analysis approaches

Researchers have argued that grouping heterogeneous linguistic profiles under a dichotomous condition might mask the cognitive effects of bilingualism. The current study used two different analysis approaches (i.e., continuous versus dichotomous) to examine inhibitory control in a sample of 239 young adult bilinguals. Dividing the sample into dichotomous groups based on L2 proficiency (i.e., high-proficient versus low-proficient) and L2 AoA (i.e., early versus late) did not lead to reliable group differences in any of the measurements used. However, the use of a continuous measure revealed that higher L2 proficiency predicted better visual inhibition and earlier L2 AoA was associated with better auditory inhibition. Furthermore, the observed differences were limited to tasks involving stimulus–stimulus competition, but not stimulus–response competition. These findings shed new light on the importance of conceptualising bilingualism as a continuous measure rather than a dichotomous measure and previous research on bilingual performance in different cognitive tasks.