Age of acquisition and proficiency as factors in language production: Agreement in bilinguals

Research on the production of subject–verb number agreement in monolinguals suggests differences between and within languages in how it proceeds as a function of morphological richness. When agreement morphology is relatively rich, the influence of conceptual number over grammatical number is less than when it is relatively poor. Within the framework of Eberhard, Cutting and Bock’s (2005) marking and morphing account of agreement production, this finding is explained by how number features from the syntax and the lexicon are reconciled. This study asks: (1) Can this account of differences in agreement production as a function of morphological richness be extended to the case of bilinguals? (2) Do age of acquisition and/or proficiency modulate whether these differences surface in bilinguals? Agreement production was examined in early and late English–Spanish, and late Spanish–English bilinguals of varying proficiency. Higher-proficiency bilinguals patterned similarly to monolinguals, supporting the extension of the marking and morphing account.