This current issue of six articles and two commentaries is based on a symposium entitled `Overcon®dence: Sources, Implications, and Solutions' that three of us (Budescu, Erev, and Wallsten) organized at the conference on Subjective Probability, Utility and Decision Making (SPUDM-15) that took place in Jerusalem in August 1995. Although based on the presentations, all submissions for this special issue underwent the standard full process of independent peer review.
To understand the symposium and these papers in the context of the recent judgment literature, it is instructive to start by distinguishing two related but distinct goals of judgment research. One goal, which has been pursued for much of the past 30 years, is to understand the relationship between human judgment and the rational prescriptions of Savage's subjective expected utility theory and the principles of Bayesian inference (Rapoport and Wallsten, 1972). The highly in¯uential research program initiated by Tversky, Kahneman, and their students in the early 1970s has focused on this rationality goal'. This line of research has generated an impressive list of empirical regularities that systematically violate certain predictions and corollaries of classic probability and utility theory. Because of their nature, some of these phenomena have been labeled biases, and a variety of simple judgmental heuristics that can explain these puzzling violations of rationality have been proposed in the literature (see the reader edited by Kahneman, Tversky, and Slovic, 1982, for a collection of seminal papers). Few research programs in recent memory have been as successful and in¯uential as the biases and heuristics' paradigm. (See, for example, Hogarth, 1987, for a list and a classi®cation of the documented cognitive biases.)
A second goal, of more recent origin, is to improve our understanding of judgment processes per se. Although this `process goal' might, in principle, be achieved as a by-product of achieving the rationality goal, many researchers now believe that this is unlikely to be the case. This belief is based on the observations that the dierences between human and Bayesian judgments are neither minor (Kahneman et al., 1982) nor consistent (Gigerenzer, 1996;Kahneman and Tversky, 1996). In addition, in many natural settings the Bayesian prescriptions are unclear (e.g. Gilat et al., 1997).
As suggested by its title, the SPUDM symposium focused on one particular judgment phenomenon Ð overcon®dence, the apparant tendency of people to believe their judgments are better than they really are. Early research on this form of `miscalibration ' (cf. Lichtenstein, Fischho, and Phillips, 1982) sought to establish the existence and boundary conditions for overcon®dence, which is indeed sometimes supplanted by undercon®dence. But more recent work has focused on describing and understanding the underlying mechanisms. Consider, for example, the review by McClelland and Bolger (1994), which lists six dierent proposed models: the stage model (