Morpheme reduplication in Japanese: A grammaticalization perspective on causative, potential, and passive constructions

This study examines the structural development and characteristics of morpheme reduplications (or doubling) in causative, potential, and passive constructions in modern Japanese. Two of these reduplication phenomena are often referred to as causative sa-insertion and potential re-insertion. However, passive ra-insertion and other longer, fully reduplicated insertions such as sase-insertion and rare-insertion are also observed. Previous studies have traced the historical development of the modern potential suffix -( r)are (Inoue 1998, Komatsu 1999, Inoue 2003), but little has been done on the recent aforementioned insertions. This study analyzes the morpheme insertions (partial and full reduplications) using data obtained from the Internet, to note their incidence and trending, as well as hypothesize why such changes may be taking place. The main focus is the causative sa-insertion---how consonant verbs are preferred over vowel verbs, how certain sentential patterns such as the benefactive -(s) ase-te-itadaku and passive-causative constructions include sa-insertion more than others, and the role sa-insertion plays in the overall historical development of the Japanese language.; The hypothesis for the insertion phenomena is that they are emerging as a form of intensifier to compensate for an "insufficiency" in meaning. For causative sa-insertion, there is a demand to increase the politeness level of the benefactive expression -( s)ase-te-itadaku. For potentials, re-insertion follows a morpheme reduction in the form of ra-deletion, where the potential form results in a shorter form. To some speakers, this reduction takes away from the potential meaning, leaving a desire for a way to add more "potentialness." These morpheme insertions fulfill a certain need for clearer, more transparent meaning. Insertions provide a more distinct, analyzable structure: -(s)aSAs- (vs. -(s)as-) for causatives, and -( r)eRE- (vs. -(r)e-) for potentials.; In addition to a longer and more transparent morpheme, insertions contribute to a millennium-long process of simplification of the conjugation paradigm. With re-insertion, and to an extent the sa-insertion, the conjugation paradigm for the consonant and vowel verbs can be united to form one conjugation paradigm for all "regular" verbs. Thus, the multiple morpheme changes over a thousand years has lead to a common morpheme and a common conjugation paradigm for all vowel and consonant verbs.