A unified account of the conjunction fallacy by coherence

We propose a coherence account of the conjunction fallacy applicable to both of its two paradigms (the M–A paradigm and the A–B paradigm). We compare our account with a recent proposal by Tentori et al. (J Exp Psychol Gen 142(1): 235–255, 2013) that attempts to generalize earlier confirmation accounts. Their model works better than its predecessors in some respects, but it exhibits only a shallow form of generality and is unsatisfactory in other ways as well: it is strained, complex, and untestable as it stands. Our coherence account inherits the strength of the confirmation account, but in addition to being applicable to both paradigms, it is natural, simple, and readily testable. It thus constitutes the next natural step for Bayesian theorizing about the conjunction fallacy.