Fundamental Frequency and Other Prosodic Cues to Topic Structure

Studies of prosody have often neglected to examine structure above the level of the utterance or sentence, yet it is becoming more and more apparent that prosody is an essential cue to the organization of longer discourses. Just as prosody helps to hold discourse together within utterances by indicating information that is new or noteworthy in some way, it also joins utterances together into groups which share the same discourse topic, or are “about ” the same thing, in discourse. However, the semantic content of this kind of joining function is still unclear in that some theories propose a gradient interpretation of topicality, while others take a more categorical approach. An example of a topic structure theory with a gradient view is the hierarchical model of Grosz & Sidner (1986). Since the simple hierarchy they propose is potentially infinitely recursive, this theory lends itself to a gradient pattern of variation, where variation depends upon the amount of active information. In this type of theory, the notion of a “topic ” as an element of the discourse structure may not be relevant at all, since the topicality relationships would be based primarily upon the dominance and subordination relationships between utterances. An alternative is proposed by Nakajima & Allen (1993) and Wichmann (2000) who suggest that topic structure can be described by four discontinuou