Japanese Children’s Acquisition of the Accusative Case: Evidence for an Interim Stage Preceding Morphological Case Acquisition

This study investigates the acquisition of the accusative marker o and case-marker drop among 2- to 3-year old Japanese children. Experiment 1 tested children’s comprehension of ga, o, and case-marker drop (indicated as ‘Ø’ below) in Wh-questions and that of ga and o in Yes/No questions. The results indicate that, while many children tended to incorrectly interpret both NP-o and NP-Ø as the agent of actions, children who correctly interpreted NP-o as patient also tended to correctly interpret NP-Ø as patient. Children in the latter group appeared to have syntactic knowledge of case-marker drop. Experiment 2 additionally used a pseudo-particle, –u, in order to test whether children who correctly interpret NP-o and NP-Ø as patient (1) have a knowledge of morphological case (the accusative case-marker o) as well as the syntactic constraints of its drop, or (2) have partial knowledge of the case-markers and grammatical relations (along with knowledge of the syntactic constraints of case-marker drop). Results indicate that some of the children in the current study can be characterized as (2). This is taken as evidence that there is a stage where children have come to understand the grammatical functions of case-markers without having a fully developed knowledge of morphological case