Most people in the world today speak more than one language. Thus, they need to decide, unconsciously, which language to use at any given time. This project aims to understand how healthy adult bilinguals resolve competition from their unintended language to communicate successfully in the intended language. In both bilingual language comprehension and production, the project will characterise the role of an under-explored linguistic dimension, lexical tone, in cross-language processing. Expected outcomes include enhanced understanding of bilingual communication and theories of bilingual language use, and practical implications for optimal language learning for bilinguals and intervention for clinical populations who speaks two languages.