Abstract
This article examines the use of non-standard polite forms of verbs by L2 learners of Japanese, using a cross-sectional spoken learner corpus called KY-corpus. It demonstrates that semi-polite verbs, which are made up of plain forms of verbs plus the polite copula desu, develop over ACTFL-OPI proficiency scales by forming a conjugational paradigm that consists of affirmative nonpast, affirmative past, negative non-past, and negative past forms, with no indication of L1 transfer. The complete paradigm appears in the utterance of learners with advanced level proficiency. The study also shows a comparison of the development of the semi-polite verbs with that of standard polite verbs or other non-standard polite expressions, and proposes a hypothesis about acquisition and the order of development of a variety of polite expressions. Based on the result of this study, I attempt to account for the reason why L2 learners can acquire and develop paradigmatic uses of the semi-polite verbs.
