Project Summary/Abstract In the last two decades, researchers have made a series of discoveries about bilingualism that have advanced our understanding of the relations between language, cognition, and the brain. One is that the two languages compete for selection, suggesting bidirectional cross-language influences. Another is that using two or more languages has consequences for cognitive functioning across the lifespan. However, this research has only focused on the long-term consequences of bilingualism. Therefore, we do not yet understand how bilinguals draw from domain-general cognitive resources to enable the use of language in real time. Moreover, although heritage speakers and second-language learners are the predominant force of dual-language users in the US, most of the research examining the consequences of bilingualism comes from populations that are not representative of such experience in the US. The proposed research seeks to exploit convergence across two topics that have been largely studied in isolation: the consequences of bilingualism on language processing, and the consequences of bilingualism on cognition. Spanish-English bilinguals who are heritage speakers and are immersed in an English-dominant environment will be examined and compared to Spanish-English bilinguals immersed in a Spanish-dominant environment. Likewise, advanced classroom learners of Spanish will be compared to advanced learners of Spanish who are immersed in a Spanish-dominant environment while studying abroad. Two experiments will be conducted using a recently-developed cross-task adaptation paradigm that interleaves a Stroop task with a language processing task. This paradigm will allow us to measure how conflict experienced in a cognitive task affects conflict experienced during language processing (i.e., conflict adaptation), and to determine whether language immersion status modulates such conflict adaptation. In Experiment 1, electrophysiological responses (using Event-related-potentials; ERPs) will be examined while participants name pictures in Spanish and English. In Experiment 2, eye-tracking will be used to examine how participants process syntactically complex sentences while reading in each language. Unlike most previous research, where only one language and one linguistic feature is examined, this project will examine different linguistic features in both of a bilingual’s languages (i.e., lexical access in production and sentence processing during reading).