Japanese intonation units and syntactic structure

This paper examines the preferred syntactic structure of the idea-conveying substantive "intonation unit" (IU) in conversational Japanese. It was found that (a) the clause is the syntactic exponent of the Japanese substantive IU; (b) the clauses are overwhelmingly single-IU clauses rather than multi-IU clauses; and (c) the multi-IU clauses exhibit a higher proportion of multiple new NPs than the single-IU counterparts. The results show that despite claims to the contrary, conversational Japanese cannot be regarded as "highly fragmented", but basically conforms to the "one IU, one clause" strategy. It is argued that the One New NP per IU Constraint is an information-flow factor motivating toward the "marked" production of multi-IU clauses, that is, the breakup of a clause into phrasal IUs.