The Development of Japanese Case-markers Observed through Children’s Comprehension of Single-Argument Sentences

Abstract

This study investigates children’s comprehension of a single-argument sentence that contains either a subject or a direct object of a transitive verb. Adopting the picture-selection task, Experiment 1 reveals 90% accuracy by the oldest group of children (mean age=5;11). This indicates that children have acquired the grammatical knowledge of ga and o by this age and that their competence is reflected in their linguistic performance. In contrast, the results disclose poor performance by the younger groups of children. Their errors were observed on the accusative case-marking more frequently than on the nominative case-marking. This asymmetry seems to reflect the developmental difference between the two case-markers: Nominative ga is acquired earlier than accusative o. In order to explore whether or not this asymmetry is rooted in the children’s grammatical knowledge, Experiment 2 tries to eliminate the effects of agent priority, a possible bias for the children’s agent interpretation of the single argument. For this purpose, test sentences were provided with discourse context in the picture-selection task. The results show that the children’s performance greatly improved with the asymmetry between the nominative and accusative cases removed. These results suggest that the performance factor overrides children’s grammatical knowledge in Experiment 1, and that the elimination of the agent bias discloses their linguistic competence in Experiment 2. However, the percentages of correct responses by the younger groups of children (age range=3;7–5;7) in the second experiment do not reach those of the oldest group in the first experiment, suggesting that they are still in the developmental process of acquiring the nominative and accusative case-markers.