Discrepancies between normative and descriptive models of decision making and the understanding/acceptance principle.

Several tasks from the heuristics and biases literature were examined in light of Slovic and Tversky's (1974) understanding/acceptance principle-that the deeper the understanding of a normative principle, the greater the tendency to respond in accord with it. The principle was instantiated both correlationally and experimentally. An individual differences version was used to examine whether individuals higher in tendencies toward reflective thought and in cognitive ability would be more likely to behave normatively. In a second application of the understanding/acceptance principle, subjects were presented with arguments both for and against normative choices and it was observed whether, on a readministration of the task, performance was more likely to move in a normative direction. Several discrepancies between performance and normative models could be explained by the understanding/acceptance principle. However, several gaps between descriptive and normative models (particularly those deriving from some noncausal base rate problems) were not clarified by the understanding/acceptance principle-they could not be explained in terms of varying task understanding or tendencies toward reflective thought. The results demonstrate how the variation and instability in responses can be analyzed to yield inferences about why descriptive and normative models of human reasoning and decision making sometimes do not coincide.