Intentions and Plans in Decision and Game Theory

Given the important role that intentions play in the way we make decisions, we would expect intentions to occupy a substantial place in any theory of action. Surprisingly enough, in what is perhaps the most influential theory of action, rational choice theory, explicit reference is made to actions, strategies, information, outcomes and preferences but not to intentions. This is not to say that no attention has been paid to the relation between rational choice and intentions. On the contrary, a rich philosophical literature has developed on the relation between rationality and intentions (see for example [10]). However, to our knowledge, there has been no real attempt to model the role of intentions in decision making within a rational choice framework. In this paper we argue that such modelling is a worthwhile enterprise. Starting from a very simplistic rational choice model, we show that enriching it with tools to represent intentions helps to account for known phenomena such as focal points, and gives rise to new questions about intention-based strategic interactions. We build our representation of intention on the philosophical foundations laid down in [2]. Our contribution is twofold. We first show that intentions can account for focal points in decisions and games. We then show how agents can use their intentions to simplify decision problems. In neither part do we go into the question whether intentions can be defined in terms of strategies, preferences, beliefs, or in any other ingredient of the existing models; we simply introduce intentions as an extra parameter and then examine some conditions that might be imposed on them.