73% of the observed bilingual (dis)advantageous effects on cognition stem from sociolinguistic factors: A systematic review

Abstract

Being bilingual confers certain behavioral adaptations. The two ongoing discussions that surround their occurrence concern the type of the effect and its origin. The former can be analyzed in terms of three outcomes: positive, negative, and null. The status of the latter is less clear. While many studies recognize some interaction of cognitive factors with social factors such as socio-economic status and sociolinguistic prestige, these observations are often made in passing and lack critical detail. Consequently, it has not been yet determined what degree of the reported bilingualism-related behavioral adaptations derive primarily from sociolinguistic factors. This systematic PRISMA-based review addresses this question. Analyzing the results of 368 studies, we find that 73.41% of the 267 studies that report bilingual adaptations attribute them either to sociolinguistic factors alone or to the interaction of sociolinguistic factors with cognitive factors. Linking the two debates, type of effect and origin of effect, this systematic review finds a previously unreported correlation: Studies that find evidence for bilingual disadvantages are more likely to claim a sociolinguistic origin, while studies that report bilingual advantages are more likely to link their findings to a cognitive origin. We discuss these results and present the key components of a sociolinguistic theory of the origin of bilingual effects.