Colloquium today (Friday October 18), 3:30PM: Alex Lascarides

Alex Lascarides (Edinburgh) will give a colloquium today (Friday Oct. 18) at 3:30PM in the Greenberg room, followed by a departmental social.


Abstract: In this talk I will present joint work with Nicholas Asher.  Our aim is to model conversation when people have conflicting goals; for instance, courtroom cross examination and political debate.  I’ll use naturally occurring dialogues to introduce a particular kind of deception, where the speaker doesn’t explicitly lie, but he implies a falsehood that he can subsequently deny was a part of his message. This motivates a new concept, that of SAFETY in discourse interpretation: one needs the means to test whether an implicature in non-cooperative conversation can be treated as a matter of public record.

We’ll propose two alternative ways of modelling both cooperative and non-cooperative conversation, both of which offer an analysis of safety.  The first model uses standard techniques from game theory. The second is a proof theoretic analysis which improves on the standard game theory version by fully supporting reasoning about what utterances need to be a part of the definition of the `interpretation game’.  In effect, it can distinguish between an utterance that a speaker contemplated but chose not to perform from an utterance that he didn’t contemplate performing at all.

This proof theoretic analysis not only models safety but also provides the means to prove a correspondence Gricean principles of cooperative conversation (e.g., Sincerity) and a situation where the preferences of the conversational participants are normally aligned.  Thus Gricean models of implicature are a special case in our framework.

Next colloquium: Esli Kaiser, November 1.