Multilingual first language acquisition refers to the language development of children exposed to two or more languages from birth or shortly thereafter. Much of the research on this topic adopts a comparative approach. Bilinguals are thus compared with their monolingual peers, and trilinguals with both bilinguals and monolinguals; within children, comparisons are made between a child's two (or more) languages, and between different domains within those languages. The goal of such comparisons is to determine the extent to which language development proceeds along similar paths and/or at a similar rate across groups, languages, and domains, in order to elaborate upon the question of whether these different groups acquire language in the same way, and to evaluate how language development in multilingual settings is influenced by environmental factors. The answers to these questions have both theoretical and practical implications.
The goal of this article is to discuss the results of some of this recent research on multilingual first language acquisition by reviewing (a) properties of the developing linguistic system in a variety of linguistic domains and (b) some of the characteristics of multilingual first language acquisition that have attracted attention over the past five years, including cross-linguistic influence, dominance, and input quantity/quality. Trilingual first language acquisition is covered in a dedicated section.