Factors Causing Overpassivisation of Unaccusative Verbs by Japanese Learners of English

It has been reported that second language (L2) learners of English including Japanese learners of English (JLEs) overpassivise unaccusative verbs although it is a kind of intransitive verbs. In order to account for the phenomenon, several assumptions have been proposed. However, so far, it is unclear which assumption is the most effective for explaining the overpassivisation of unaccusatives. Thus, this study tries to examine which of the three factors, animacy of subjects, existence of conceptualizable agents, or telicity of verbs, the most strongly affects overpassivisation of unaccusative verbs by JLEs. In this study, we conducted two experiments to examine this question. Study 1 was conducted with 100 university JLEs to compare the effect of animacy of subjects with that of the existence of conceptualizable agents. As a result, it was found that the animacy of subjects more strongly affected the overpassivisation of unaccusatives than the existence of conceptualizable agents. We conducted Study 2 with 101 university JLEs to examine which of the two factors, the existence of conceptualizable agents or the degree of telicity, is more influential. The results showed that the former was influential, but the latter was less so on the overpassivisation of unaccusatives. From the results of the two experiments, we concluded that the animacy of subject is the strongest influential factor among the three. On the other hand, the telicity of verbs hardly influences any errors.