L2 acquisition of interface properties: Case of Japanese wa and ga

Abstract

This study investigates the second language (L2) acquisition of interface properties, with special focus on the Japanese particles wa and ga. The choice between wa and ga, which are often referred to as 'topic marker' and 'nominative case marker' respectively, is under influence of semantic (e.g. Noda 1996, Masuoka 1987) and discourse (e.g. Kuno 1975) information; in other words, it is a multiple-interface property (Montrul 2011). Based on the vulnerability in L2 acquisition of interface properties reported in previous studies (e.g. Sorace 2005), it is predicted that the difficulty in the L2 acquisition of wa and ga also stems from its characteristics as an interface property. It has also been argued that interface properties can cause residual difficulties at the near-native level and might not be fully acquirable by L2 speakers, i.e. Interface Hypothesis (Sorace and Filiaci 2006). However, in previous studies on L2 acquisition of wa and ga, the affecting factors on the choice between these particles have been mainly examined individually and not enough attention has been paid to the potential interactions between these factors. Therefore, how multiple-level factors affect Japanese L2 learners' choice between wa and ga remains a mystery. In order to uncover this mystery, the current study investigates the effect of various factors and their interactions on Japanese L2 learners' use of wa and ga. 134 L1 English / L2 Japanese speakers with beginner, intermediate, advanced and upper-advanced proficiency levels and 36 Japanese native speakers participated in an online cloze test. These participants were instructed to choose either wa or ga to mark a nominative NP in experimental sentences that were under various semantic and discourse conditions. The collected data was analysed statistically using binomial logistic regression. The results show significant interactions between a discourse factor on one hand and semantic factors on the other in L2 grammar, which means that the effect of discourse on the choice between wa and ga varies depending on the semantic characteristics of the sentence. The results of the follow-up interviews, which were conducted with 10 participants with various proficiency levels, also support these statistical results. Further, the results indicate that the difference between native and non-native speakers is mainly caused by non-native speakers' lower ability to reflect discourse information onto the choice of particle, which results in higher susceptibility to semantic factors. Finally, the results show that there is a significant gap between native speakers and upper-advanced speakers in their ability to process large amount of discourse information, providing supporting evidence to the Interface Hypothesis.