Event-related brain potentials and second language learning: syntactic processing in late L2 learners at different L2 proficiency levels

There are several major questions in the literature on late second language (L2) learning and processing. Some of these questions include: Can late L2 learners process an L2 in a native-like way? What is the nature of the differences in L2 processing among L2 learners at different levels of L2 proficiency? In this article, we review studies that addressed these questions using event-related brain potentials (ERPs) in late learners and that focused on syntactic processing. ERPs provide an on-line, millisecond-by-millisecond record of the brain's electrical activity during cognitive processing. ERP measures can thus provide valuable information on the timing and degree of neural activation as language processing (here: syntactic processing in L2) unfolds over time. After discussing the use of ERPs for the study of L2 learning and processing, we review electrophysiological studies on syntactic and morphosyntactic processing in late L2 learners with different levels of L2 proficiency. The currently available evidence indicates that patterns of neural activity in the brain during syntactic and morphosyntactic processing can be modulated by various, possibly interrelated, factors including the similarity or dissimilarity of syntactic structures in L2 and L1, the exact nature of the syntactic structure L2 learners seek to comprehend and the concomitant expectancies they can generate with regard to violations in this structure, and the L2 learners' level of L2 proficiency. Together these studies show that ERPs can successfully elucidate subtle differences in syntactic processing between L2 learners and native speakers, and among L2 learners at different levels of L2 proficiency, which are difficult to detect or that might have remained undetected with behavioural measures.