A Phonological Study on Japanese Discourse Markers

Language, Information and Computation(PACLIC 11), 1996, 297-306 A Phonological Study on Japanese Discourse Markers Masahito KAWAMORI Akira SHIMAZU Takeshi KAWABATA fkawamori, shimazujOatom.brl.ntt.co.jp, kawOidea.brl.ntt.co.jp NTT Basic Research Laboratories 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa, 243-01 Japan Abstract A spontaneously spoken, natural Japanese discourse contains many instances of the so-called redundant interjections and of back- channel utterances. These expressions have not hitherto received much attention and few systematic analyses have been made. We show that these utterances are characterizable as discourse mark- ers, and that they comprise a well-defined category, characterizable in a regular manner by their phonologico-prosodic properties. Our report is based on an experiment involving spontaneously spoken conversations, recorded in a laboratory environment and an- alyzed using digital devices. Prosodic patterns of discourse mark- ers occurring in the recorded conversations have been analyzed. Several pitch patterns have been found that characterize the most frequently used Japanese discourse markers. 1 Introduction A spontaneously spoken, natural Japanese discourse contains many features which are not part of its written counterpart: disfluencies, interjections, re- pairs, non-sentential particles, and checked utterances. Aizuchi, or back-channel utterances, and other so-called redundant utter- ances, such as hai, un, anoo and ee, which are counterparts of the English "uh-huh", "yes", or "ok", are especially abundant in Japanese discourse. These are often taken as the manifestation of the irregularity and non- systematic nature of spoken language. They are traditionally considered to be spurious or meaningless, not especially contributing to language. From this point of view, these utterances would be nothing but `disfluencies', some kind of 'noise'. Yet we believe these utterances have important functions in discourse, com- parable in many respects to what is called discourse markers. In this paper, we show that these utterances are indeed characterizable as discourse markers, and that they comprise a well-defined category, characterizable in a regular manner by their phonologico-prosodic properties. These expressions are important because, among other things, they often provide informatiQn about the structure of discourse they occur in and about the speaker's intention or plan. Sidner 1985 states that discourse markers are necessary for recognizing the relations between the intended acts and the 297 overall plans of the speaker. A number of researchers have noticed the rela- tion between discourse structure and intonational, or prosodic, characteristics. Grosz and Hirschberg 1992, using an independently motivated theory of dis- course model, show that there are significant associations between intonational features and discourse structure. Similarly, Nakajima and Allen 1992 discuss the correlation between prosodic information and the topic structure of dis- course. One of the first works to discuss the relation between discourse markers and prosody, in the context of discourse structure, is Hirschberg and Litman 1987. Based on a study of "now" in natural recorded discourse, Hirschberg and Litman propose that, in speech, intonational characteristics play a crucial role in distinguishing between cue and non-cue uses, helping to disambiguate the structure of a discourse. We are interested in these Japanese discourse markers for various reasons. First of all, in order to understand and explain the …

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