TEMPORAL CHARACTERISTICS OF UTTERANCE UNITS AND TOPIC STRUCTURE OF SPOKEN DIALOGS

There are various difficulties in processing spoken dialogs because of acoustic, phonetic, and grammatical ill-formedness, and because of in teractions among participants. This paper describes temporal character istics of utterances in human-human task-oriented dialogs and interact ions between the participants, analyzed in relation to the topic struc ture of the dialog. We analyzed 12 task-oriented simulated dialogs of ASJ continuous speech corpus conducted by 13 different participants wh ose total length being 66 minutes. Speech data was segmented into utte rance units each of which is a speech interval segmented by pauses. Th ere were 3876 utterance units, and 38.9% of them were interjections, f illers, false starts and chiming utterances. Each dialog consisted of 6 to 15 topic segments in each of which participants exchange specific information of the task. Eighty-six out of 119 new topic segments sta rted with interjectory utterances and filled pauses. It was found that the durations of turn-taking interjections and fillers including the preceding silent pause were significantly longer in topic boundaries t han the other positions. The results indicate that the duration of int erjection words and filled pauses is a sign of a topic shift in spoken dialogs. In natural conversations, participants' speaking modes chang e dynamically as the conversation develops. Response time of both clie nt and agent role speakers became shorter as the dialog proceeded. Thi s indicates that interactions between the participants become active a s the dialog proceeds. Speech rate was also affected by the dialog str ucture. initiating and terminating parts where most utterances are of fixed expressions, and slow in topic segments of the body part of the dialog where both client and agent participants stalled to speak in or der to retrieve task knowledge. The results can be utilized in man-mac hine dialog systems, e.g., in order to detect topic shifts of a dialog , and to make the speech interface of dialog systems more natural to a human participant.