Learning a new language as an adult is difficult and many fail to acquire high proficiency. Individual differences in late language learning have been partially, but not fully, accounted for by factors such as working memory and native language (L1) performance. An overlooked observation in research that attempts to characterize successful language learning is that bilinguals consistently outperform monolinguals in acquiring new languages. When bilinguals are learning a new language, they can draw on their past experience. That experience encompasses both language-specific skills, such as managing the dynamics of cross-language interaction, as well as domain-general learning skills that may enable language regulation and control. In contrast, for monolingual learners, there is only the opportunity to transfer existing L1 knowledge and general cognitive skills. The hypothesis tested in the research I will present is that previous language experience and individual differences guide the trajectory and outcome of new language learning. In one study, I consider how biases in domain-general learning contribute to individual differences in language processing for monolinguals and bilinguals with different language learning experience. In a second study, I examine the consequences of domain-general and language-specific biases for bilinguals and monolinguals as they learn a new language.