Coherence in Spoken Discourse

This paper explores the possibilities and limits of a discourse grammar applied to spontaneous speech. Most discourse grammars (e.g. SDRT, Asher, 1993; RST, Mann & Thompson, 1988) tend to be descriptive theories of written discourse which presuppose a coherent structure. This structure is the outcome of a goal directed planning process on the part of the producer. In order to obtain a better understanding of the planning process we analyse spoken discourse elicited in an experimental setting. Subjects describe the pixel-per-pixel development of sketchmaps on a computer screen. This forces the speakers to conceptualise the perceived state of affairs, plan their discourse, and produce a description of the drawing at the same time. Thus we find evidence for the planning process in the recorded data and can show that the discourse structures are less globally coherent than those underlying written text. In our paper we discuss to what extent a flexible discourse grammar based on a Tree Description Grammar (TDG) (Schilder, 1997) can handle such data.