Many learners of a foreign language struggle to correctly pronounce newly-learned speech sounds so that they can be understood by native listeners. Yet many others achieve this with apparent ease. What is responsible for these large individual differences in phonetic aptitude? Are better speakers also better listeners? The aim of this proposal is to determine whether there is a link between skills in production and skills in perception in learners of a foreign language. A special focus of the research will be to compare bilingual with monolingual learners, because bilinguals have had more experience with linguistic variation than monolinguals, and therefore might have greater phonetic aptitude. Bridging traditional linguistic and newer cognitive neuroscience approaches, the proposed study will determine the behavioural and brain bases for phonetic production and perception abilities.