Proceedings of the Annual Meeting of the Cognitive Science Society

There are two major problems associated with propagation of uncertainty in the rule-based modeling of human reasoning. O n e concerns how the possibly uncertain evidence in a rule's antecedents affects the rule's conclusion. The other concerns the issue of combining evidence across rules having the same conclusion. Two experiments were conducted in which psychological data were compared with a variety of mathematical models for managing uncertainty. Results of an experiment on the fu-st problem suggested that the certainty of the antecedents in a production rule can be summarized by the maximum of disjunctively connected antecedents and the minimum of conjunctively connected antecedents {maximin summarizing), and that the m a x i m u m certainty of the rule's conclusion can be scaled down by multiplication with the results of that summary{multiplication scaling). A second experiment suggested that the second problem can be solved with Heckerman's modified certainty factor model which sums the certainties contributed by each of two rules and divides by 1 plus their product.