Optimization of the verbal inflectional paradigm by the cyclic application of morphophonological processes: Evidence from potential forms in Japanese

In Japanese, a series of morphophonological changes that reorganizes the verbal inflectional paradigms is currently underway. The changes in potential forms involve two innovative processes: Ar-Deletion and re-Insertion. This paper analyzes these morphophonological changes in the Japanese potential forms, and models the mechanism that governs the sequential changes, using the Corpus of Spontaneous Japanese. By positing a chronological order between the changes, I argue that the initial change in consonant-final verbs is motivated by semantic disambiguation, and the subsequent change in vowel-final verbs is triggered by analogical leveling for the optimization of the conjugation paradigm. This analogical leveling reorganizes the paradigm in order to counter the increased discrepancy between potential forms of consonant-final verbs and vowel-final verbs caused by the previous change. I propose that positing this two-step process is crucial to understanding the diachronic changes at issue.