In the history of psycholinguistics, there are traditional accounts that have been told about language learning and processing. These accounts revolve around the constraints imposed by the age of language learning and by universal principles that are assumed to be natively given. The contribution of Brian MacWhinney and his collaborators has been to challenge the fundamental principles on which these traditional accounts rest. By taking an emergentist approach that assumes that variation in learning will better inform foundational mechanisms than fixed constraints, they shifted the focus from language development in monolingual speakers to a broader consideration of cross-linguistic and cross-language contexts. We have been beneficiaries of this shift. In this paper, we describe research on bilingualism that examines two key mechanisms within the MacWhinney framework: Competition and transfer. We argue that what we have learned about bilingual language processing supports the central role of competition and its broad consequences. We claim that one of these consequences has been to reframe questions of transfer to consider the requirement that bilingual speakers regulate their two languages. The dynamic nature of cross-language interactions across languages and across varied language environments reflects the deep plasticity associated with language and its cognitive and neural bases.