L2 acquisition of discourse constraints on the use of Japanese pronouns

Previous studies have suggested that ambiguous null pronouns are biased to co-refer with topical subject antecedents. In Italian, for example, Belletti, Bennati & Sorace (2007) (henceforth BB&S) suggested that null subject pronouns typically co-refer with already established topic antecedents ([topic shift]), whereas overt subject pronouns signal a change in topic ([+topic shift]). This discourse constraint on overt pronouns is not observed in non-null subject languages such as English. BB&S conducted an empirical study whose results were that the [+topic shift] requirement for overt pronouns is a residual problem for L1 English near native speakers of L2 Italian. In order to test the applicability of findings in BB&S, this study looks at another null subject language, Japanese, and extends BB&S in three ways. First, two factors which affect the choice of antecedents of pronouns, namely topichood and subjecthood, are separated to find out which is more crucial in determining the antecedents of pronouns. Japanese has a topic marker, –wa, which is distinct from a nominative case marker, –ga. Therefore, topichood and subjecthood, which are confounded in Italian, can be separated. Second, not only the distribution of subject pronouns, but also that of object pronouns is tested. Japanese allows object drop as well as subject drop; accordingly, the distribution of null and overt pronouns in the object position, which is not discussed in BB&S, is investigated. Finally, this study considers the effects of surface word order of the antecedents. Japanese allows scrambling; as a result, whether the word order of the preceding nouns affects the antecedent preference of pronouns is investigated. The results of an off-line interpretation task and a written, elicited production task challenge BB&S, showing that (i) subjecthood, not topichood or word order, is crucial in determining the antecedents of null pronominal subjects in Japanese; and that (ii) the advanced L2 speakers had a different interpretation of null pronominal subjects, rather than overt pronominal subjects, compared to Japanese monolinguals. This suggests that a [-subject shift] requirement for null pronouns, not a [+topic shift] requirement for overt pronouns can be a residual problem in the L2 grammar.