Second language acquisition of morphosyntactic and discourse functions of case markers in Korean

This study investigated the extent to which second language (L2) learners experience difficulties when integrating multiple sources of information at internal and external interfaces, and how their first language (L1) influences this integration process. Two groups of L2 Korean learners, including Chinese and Japanese speakers, as well as native Korean speakers, completed a sentence-completion task and an acceptability judgment task. In the sentence-completion task, both native speakers and Japanese-speaking learners showed sensitivity to the function of case marking in distinct syntactic structures (morphology - syntax interface or internal interface), but not Chinese-speaking learners. In the acceptability judgment task, only the native speakers exhibited sensitivity to the discourse functions of case marking based on information structure (morphology - discourse interface or external interface), whereas the L2 learners did not appear to be influenced by the case-marking condition. These findings suggest that L2 integration of multiple information sources may be influenced by specific types of interfaces and L1 background.