Testing L1 effects in L2 interface acquisition

Abstract This study investigated the role of typological similarity and structural overlap in the acquisition of morphosyntax–discourse interface phenomena in L2 Korean. Two experiments examined plural marking agreement and information structure among Korean native speakers, L1-Chinese learners, and L1-Japanese learners. Experiment 1 showed that only native speakers, and not the L2 learners, showed robust sensitivity to plural marking violations, highlighting the persistent difficulty associated with integrating morphology and discourse. Importantly, the non-convergence of L1-Japanese learners, despite the typological proximity between Japanese and Korean, raised the question of whether structural overlap, rather than broad typological similarity, might be the decisive factor in interface acquisition. To address this issue, Experiment 2 investigated information structure, a domain where Japanese and Korean share fine-grained correspondences. In this experiment, L1-Japanese learners successfully aligned with the given-before-new ordering principle, whereas L1-Chinese learners did not. Taken together, the findings suggest that fine-grained structural overlap may provide a relatively facilitative advantage in L2 interface acquisition. These results point to the need to view crosslinguistic influence at external interfaces as a dynamic interaction of structural and typological factors.