LingLang Lunch (3/12/2014): Livia Polanyi (Stanford University)

Step-wise Discourse Topic Construction (joint work with Trevor Doherty and Katherine Hinton)

In 1975, Harvey Sacks, the pioneering Conversational Analyst, noted that conversation usually flows in a stepwise manner so that whatever is being introduced links up to what has just been talked about in a way that, though we’re far from where we began, as far as anybody knows, a new topic has not been started. In this way, I propose a formalization of the flow of conversation based on a novel approach to Discourse Topic (DT), and to the mechanics of Discourse Coherence, another intuitively useful pre-theoretic construct. DT, a notion often invoked to label stretches of text that seems to “go together”, is treated as an abstract, dynamic phenomenon of various levels of granularity that emerges from feature representations of sequenced individual utterances. Under this approach, Discourse Coherence, is a scalar notion: a next utterance will shift DT either suddenly when a number of features change simultaneously or more gradually when fewer features shift. Minimal shifts thus result in more coherent discourse, while more radical shifts are less so. A model of musical development is used to illustrate both the conversational phenomenon and the representational formalism we use to account for conversational topic flow. Theoretical challenges to the Linguistic Discourse Model (Polanyi et al.) and Structured Discourse Representation Theory (Asher and Lascarides) in which an Open Right Edge Tree of discourse units is used to account for discourse anaphora will be raised but, alas, left unresolved.