Pragmatic Reasoning in Bridge

In this paper we argue that bidding in the game of Contract Bridge can profitably be regarded as a micro-world suitable for experimenting with pragmatics. We sketch an analysis in which a “bidding system” is treated as the semantics of an artificial language, and show how this “language”, despite its apparent simplicity, is capable of supporting a wide variety of common speech acts parallel to those in natural languages; we also argue that the reason for the relatively unsuccessful nature of previous attempts to write strong Bridge playing programs has been their failure to address the need to reason explicitly about knowledge, pragmatics, probabilities and plans. We give an overview of Pragma, a system currently under development, which embodies these ideas in concrete form, using a combination of rule-based inference, stochastic simulation, and “neural-net” learning. Examples are given illustrating the functionality of the system in its current form. The research reported in this paper was undertaken from Summer 1989 to Summer 1991 at the Swedish Institute of Computer Science. Much of the content of the present paper, from Section 1.3 onward, appeared in almost the same form as reference [Gambäck et al 1990]. Since publication of this work, a number of advances in Computer Bridge Playing have taken place which largely follow the approach outlined here.