The acquisition of argument structures of intransitive and transitive verbs in Japanese: The role of parental input

The present study investigated the role of morphosyntactic information in the acquisition of transitive and intransitive verb argument structures (VAS) in the Japanese language, which allows massive omissions of arguments and case markers. In particular, we investigated how the 'variation sets' proposed by Kuntay and Slobin work in Japanese. Longitudinal interaction data from three Japanese-speaking mother-child pairs were collected at five different times between the ages of 0;10 and 3;01. Children's acquisition of VAS and mothers' use of verbs were examined, including morphologically related verbs in a variety of sentence frames with null and overt arguments. The results indicate that all three mothers showed an increase in overt arguments in different syntactic roles as well as lexical given arguments around the time that children started uttering words. However, the use of a variety of sentence frames with null and overt arguments was not uniform among the mothers, and such individual differences were related to the acquisition of VAS among children. These findings support the role of 'variation sets' in the acquisition of VAS in Japanese and suggest that the availability of morphosyntactic information in the input helps children to reconstruct VAS.