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M. Oaksford, N. Chater, and J. Larkin (2000) proffered a Bayesian model in which conditional inferences are a direct function of conditional probabilities. In the current article, the authors first considered this model regarding the processing of negatives in conditional reasoning. Its predictons were evaluated against a large-scale meta-analysis (W. J. Schroyens, W. Schaeken, & G. d'Ydewalle, 2001b). This evaluation shows that the model is flawed: The relative size of the negative effects does not match predictions. Next, the authors evaluated the model in relation to inferences about affirmative conditionals, again considering the results of a meta-analysis (W. J. Schroyens, W. Schaeken, & G. d'Ydewalle, 2001a). The conditional probability model is countered by the data reported in literature; a mental models based model produces a better fit. The authors conclude that a purely probabilistic model is deficient and incomplete and cannot do without algorithmic processing assumptions if it is to advance toward a descriptively adequate psychological theory.

M. Oaksford and N. Chater (1994), like several theorists before them, attributed cases in which selections in the Wason 4-card task match the prescriptions of formal logic to a special kind of deontic reasoning. They proposed that a utility model of card selection governs performance in deontic contexts. We show that such 'logical' performance can be obtained in nondeontic contexts as well, contexts in which utility cannot explain differential card selections. Our results also cannot be explained by Oaksford and Chater's information-gain model without violating a fundamental assumption of that model, the rarity assumption. Our data challenge Oaksford and Chater's framework as well as any theory of selection-task performance that attributes logic-like performance to a special kind of deontic reasoning.

M. Oaksford and N. Chater (O&C; 1994) presented the first quantitative model of P. C. Wason's (1966, 1968) selection task in which performance is rational. J. St B T Evans and D. E. Over (1996) reply that O&C's account is normatively incorrect and cannot model K. N. Kirby's (1994b) or P. Pollard and J. St B T Evans's (1983) data. It is argued that an equivalent measure satisfies their normative concerns and that a modification of O&C's model accounts for their empirical concerns. D. Laming (1996) argues that O&C made unjustifiable psychological assumptions and that a 'correct' Bayesian analysis agrees with logic. It is argued that O&C's model makes normative and psychological sense and that Laming's analysis is not Bayesian. A. Aimor and S. A. Sloman (1996) argue that O&C cannot explain their data. It is argued that Almor and Sloman's data do not bear on O&C's model because they alter the nature of the task. It is concluded that O&C's model remains the most compelling and comprehensive account of the selection task.

A critique is offered of the theory by M. Oaksford and N. Chater (1994) of rational analysis in P. C. Wason's (1966) selection task. That theory turns on the idea that participants choose among different cards according to the amount of information they expect to gain; however, Oaksford and Chater have chosen a measure of information (the Shannon-Wiener measure) that is irrelevant to the question actually put to the participants. Consequent to that choice, certain assumptions and parameter values are dictated by the rank order of selection frequencies that the theory seeks to match. Those relationships are picked out, and the mathematical assumptions are identified and transposed into their psychological equivalents. Those psychological equivalents are (a) more in number than the results to be explained and (b) psychologically implausible. Finally, a correct Bayesian analysis of the selection task is shown to confirm the prescription of propositional logic.

In 2 studies, delusional participants assigned higher probabilities to narratives of actual delusions than participants with no history of delusions; previously delusional participants did not differ significantly from delusional participants or participants with no history of delusions. In Study 2, the authors found that this reasoning bias was specific to delusions and did not generalize to 'neutral' text. Familiarity with the content of the delusion narratives played a mediating role in the estimation of their probability, but delusional status also had a significant, independent effect. These findings are consistent with the Bayesian model of delusion formation proposed by D. R. Hemsley and P. A. Garety (1986), and with R. P. Bentall, P. Kinderman, and S. Kaney's (1994) concept of 'emotional saliency.' A productive area of future research might be to further determine the elements of 'emotional saliency' and their impact on the individual steps of the Bayesian model.