Acquisition of Japanese verbal morphology: Applying processability theory to Japanese

This paper aims to identify the developmental sequence of Japanese verbal morphology in second language learners' speech production through three longitudinal studies and two cross‐sectional studies as well as to explain this sequence within the framework of Pienemann's Processability Theory (1998). Research questions to be answered include: (1) What is the hypothesised developmental sequence of Japanese verbal morphology in learners' speech production in a L2 context based on Processability Theory? (2) What is the actual developmental sequence of Japanese verbal morphology achieved by the learners? (3) Does this sequence match the hypothesised developmental sequence? Results from the study indicate that verbal morphology in Japanese is acquired in a fixed order and that the order is predictable through identification of the hierarchy of processing prerequisites for sentence production. Such results have a practical and theoretical implication for the research of Japanese as a second language.