Two types of detransitive constructions in the dialects of Japanese

The Hokkaido dialect of Japanese, spoken in the northern island Hokkaido, has two detransitivizing strategies, namely passivization and spontaneous construction formation. Passive and spontaneous morphemes share the function of demoting the transitive subject, although different strategies are used in each case. In passive constructions, transitive subjects are demoted and they may appear as elements with oblique case. In spontaneous constructions, however, the transitive subjects are completely removed. This paper argues that this difference in the subject demotion strategy is motivated by the aspectual differences between the two detransitive constructions. It will be shown that the agent removal in spontaneous constructions is imposed by the simplification of the logical structure of the predicate while the subject demotion (to oblique status) in passive constructions is not.