Effects of working memory capacity and distance-based complexity on agreement processing: a crosslinguistic competition account

Abstract This study examined the extent to which working memory (WM) capacity and distance-based complexity influenced how second language (L2) learners used morphosyntactic information incrementally during online processing of L2 English long-distance subject-verb number agreement dependencies. The moving-window self-paced reading experiment involved 40 agreement-lacking first language (L1) Thai learners of English and 40 native English speakers. Distance-based complexity was manipulated based on whether the agreement controller and the agreeing verb were intervened by a short-distance subject-extracted relative clause or a long-distance object-extracted relative clause in line with the Dependency Locality Theory. The findings indicated that both native speakers and L2 learners experienced less processing difficulty in short-distance conditions, showing heightened sensitivity to agreement violations. Their sensitivity was, however, modulated as a function of distance-based complexity and WM capacity. The L2 learners’ lack of sensitivity in the long-distance conditions was associated with their limited pool of cognitive resources. Consistent with the L1–L2 structural competition account, these findings suggest in relation to morphology learning in SLA that L2 learners may labor under parallel activation during crosslinguistic competition, whereby cognitive resources are insufficient to resolve long-distance agreement dependencies, thus resulting in reduced sensitivity to L2 morphosyntactic violations.