Diversity in Multilingual Learners: How Variation in Learners and Contexts for Learning Shape the Acquisition and Processing of an L3/Ln

In this chapter we review current research on how the experiences that multilingual learners bring to language learning may shape the trajectory and outcome of learning an L3/Ln. While there is abundant evidence that the particular languages that individuals speak contribute to the process of new language learning, and evidence that multilingualism may enhance new learning, there is now emerging research demonstrating that the cognitive and neural mechanisms that enable bilinguals and multilinguals to use two or more languages effectively may also contribute to the course and consequences of new language learning. The dynamic activation of all of the languages that a speaker uses and interactions across languages shape not only language processing but also new learning. We identify sources of variation among learners and across the contexts in which learning occurs to consider how language learning might reflect multilingual experience.