Experimental investigation of end-of-utterance perception by final lowering in spontaneous Japanese

It is considered that final lowering, which is a phenomenon that the fundamental frequencies (F0s) fall significantly in sentence-final position, marks the end of an utterance in Japanese. However, it is not clear whether the hearer utilizes final lowering to recognize the end of the utterance. In this paper we investigated effect of final lowering on the perception of an end-of-utterance in spontaneous Japanese speech. We adopt a Bayesian hierarchical model to estimate final accentual phrases or utterance-final elements related to the end of the utterance from prosodic features. Results suggested that final lowering was associated with the syntactic elements mostly placed at the end of a Japanese utterance, but not with the end-of-utterance itself. We, then, carried out perceptual experiments using Japanese utterances with modified F0s either in the middle or at the end. The results showed that the subjects detected the end of the utterance even in the absence of final lowering and were not affected by the presence of an F0 downstep simulating the final lowering in the middle of the utterance. That suggests that Japanese hearers do not use final lowering to perceive the end of an utterance.