Abstract This study tested the applicability of the Interface Hypothesis by investigating the acquisition of discourse constraints concerning Japanese pronouns. It extends previous studies on second language (L2) Italian in three ways. First, the two factors affecting the choice of antecedents for pronouns, topichood and subjecthood, were separated to determine the more crucial one. Second, it investigated the distribution of subject and object pronouns. Third, it considered the effects of the antecedents’ surface word order. The written interpretation and production tasks show that (i) subjecthood is crucial in determining antecedents for null pronominal subjects in Japanese, not topichood or word order, and (ii) L2 grammar is not different from monolingual grammar except when interpreting specific null pronominal subjects, attributable to a task effect. The latter fails to support the Interface Hypothesis but supports the view that all aspects of the discourse-syntax interface are not necessarily problematic in L2 acquisition.
Tokiko Okuma (2026) studied this question.