The Search for Sim p licity: A Fundam ental Cogn itive Princip le?

It is proposed that the cognitive system imposes patterns on the world according to a simplicity principle: Choose the pattern that provides the briefest representation of the available information. T he simplicity principle is normatively justi ® edÐ patterns that sup-por t simple representations provide good explanations and predictions on the basis of which the agent can make decisions and actions. M oreover, the simplicity principle appears to be consistent with empirical data from many psychological domains, including perception, similarity, learning, memory, and reasoning. T hus, the simplicity principle promises to serve as the star ting point for the rational analysis of a wide range of cognitive processes, in Anderson’s (1990, 1991a) sense. T he simplicity principle also provides a framework for integrating a wide range of existing psychological proposals. T he cognitive system must cope with a world that is immensely complex but that is, nonetheless, highly patterned. T he patterns are crucial. In a completely random world, prediction, explanation, and understand ing wou ld be impossibleÐ there wou ld be no patterns on which prediction could be based, to wh ich explanations could refer, or the comprehension of which could amount to understanding. Even more fundamentally, without any patterns relating actions to consequences, there would be no basis to choose one action r ather than another. T he ability to ® nd patterns in the world is therefore of central impor tance throughout cogn ition. Without the ability to ® nd such patterns an agent might as well be in a random world: It would be able to predict, explain, and understand nothing; and it would have no basis on which to choose its actions. By contrast, the cognitive systems of people an