Asymmetric belief sensitivity and justification explain the Wells Effect

Wells (1992) found that jurors are more likely to find a defendant guilty when the evidence against them is 'specific' (that is, when the evidence provides a causal mechanism for how an event occurred) as opposed to being based on base-rate information, or what Wells calls 'general' evidence. Enoch, Spectre, and Fisher (2012) propose that this epistemic difference can be explained by the “sensitivity” of beliefs formed on the basis of these two types of evidence where sensitivity is understood as a counterfactual condition on knowledge judgments. They argue that beliefs are sensitive when formed on the basis of specific evidence, but not when they are formed on the basis of general evidence. In two preregistered experiments, we tested this hypothesis. We replicated an earlier finding that specific, as opposed to general evidence, is more likely to lead to knowledge judgments. Consistent with the hypothesis of Enoch and colleagues, we also found that sensitivity partially mediates the relationship between evidence type and knowledge attributions.