Looking for default vocabulary insertion rules: Diachronic morphosyntax of the Japanese addressee-honorification system

As opposed to syntactic operations (such as Merge), morphology has been seen as the source of language variation. But few attempts have been made in the field of Distributed Morphology to explicitly and formally identify the role of postsyntactic rules in language change. By analyzing the change in the Japanese addressee-honorification system (Yamada 2019c), this paper proposes that the emergence of the new grammar - which seems to be an instance of a microparametric change in the Agree operation (Kayne 2000; 2005; Biberauer & Roberts 2012; Barbiers 2013) - is, in fact, explained as a morphological reanalysis: the reanalysis is caused by overgeneralization of vocabulary insertion rules resulting from abductive reasoning in pursuit of default rules. It is also suggested from a quantitative corpus survey using Time Series Analysis (the Dynamic Generalized Linear Mixed Effects Model) that the reanalysis is facilitated particularly in the configuration where the addressee-honorific marking is immediately followed by a sentence-final particle.