How does bilingualism matter? A meta-analytic tale of two hemispheres

Abstract

The present investigation evaluates the effects of multiple language acquisition history on brain functional organization for language. To address a range of findings concerning the functional cerebral lateralization of the native (L1) and second languages (L2) of bilinguals, a meta-analysis was conducted on 71 studies that used behavioral paradigms to assess bilingual laterality. The predictive value of a number of theoretically identified moderators of cerebral asymmetry for language was assessed, namely, the age of second language (L2) acquisition, fluency in theL2, participant sex, experimental paradigm, linguistic task demands, relatedness of L1 and L2 structures, and context of language use. The results revealed no differences in the laterality of first and second languages within L2 acquisition age groups. Of the moderators tested, age of L2 acquisition was identified as the most reliable predictor of the direction of laterality. The conditions under which systematic similarities and differences in language lateralization among bilingual subgroups emerge are discussed in terms of implications for current models and theories concerning the functional organization of language in the bilingual brain.