Scalar implicatures and iterated admissibility

Paul Grice has given an account of conversational implicatures that hinges on the hypothesis that communication is a cooperative activity performed by rational agents which pursue a common goal. The attempt to derive Grice’s principles from game theory is a natural step, since its aim is to predict the behaviour of rational agents in situations where the outcome of one agent’s choice depends also on the choices of others. Generalised conversational implicatures, and in particular scalar ones, offer an ideal test bed for this working hypothesis, since with this kind of implicatures the alternative choices available to the agents are less dependent on context, and they can be derived from the meanings of the sentences employed. Some rival game-theoretic accounts of the same phenomena will be criticised. The present paper shows that scalar implicatures can be explained using iterated admissibility, but that some of these need an additional assumption in order to be accounted for.