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This study investigates how judgments of explanatory powerare affected by (i) the prior credibility of a potentialexplanation, (ii) the causal framing used to describe theexplanation, and (iii) the generalizability of the explanation.We found that the prior credibility of a causal explanationplays a central role in explanatory reasoning: first, because ofthe presence of strong main effects on judgments ofexplanatory power, and second, because of the gate-keepingrole prior credibility has for other factors. Highly credibleexplanations were not susceptible to causal framing effects.Instead, highly credible hypotheses were sensitive to thegeneralizability of an explanation. While these results yield amore nuanced understanding of the determinants ofjudgments of explanatory power, they also illuminate theclose relationship between prior beliefs and explanatorypower and the relationship between abductive andprobabilistic reasoning.

Explanation is a central concept in human psychology. Drawing upon philosophical theories of explanation, psychologists have recently begun to examine the relationship between explanation, probability and causality. Our study advances this growing literature at the intersection of psychology and philosophy of science by systematically investigating how judgments of explanatory power are affected by (i) the prior credibility of an explanatory hypothesis, (ii) the causal framing of the hypothesis, (iii) the perceived generalizability of the explanation, and (iv) the relation of statistical relevance between hypothesis and evidence. Collectively, the results of our five experiments support the hypothesis that the prior credibility of a causal explanation plays a central role in explanatory reasoning: first, because of the presence of strong main effects on judgments of explanatory power, and second, because of the gate-keeping role it has for other factors. Highly credible explanations are not susceptible to causal framing effects, but they are sensitive to the effects of normatively relevant factors: the generalizability of an explanation, and its statistical relevance for the evidence. These results advance current literature in the philosophy and psychology of explanation in three ways. First, they yield a more nuanced understanding of the determinants of judgments of explanatory power, and the interaction between these factors. Second, they show the close relationship between prior beliefs and explanatory power. Third, they elucidate the nature of abductive reasoning.