Best, Second-Best, and Good-Enough Explanations: How They Matter to Reasoning

There is a wealth of evidence that people's reasoning is influenced by explanatory considerations. Little is known, however, about the exact form this influence takes, for instance about whether the influence is unsystematic or because of people's following some rule. Three experiments investigate the descriptive adequacy of a precise proposal to be found in the philosophical literature, to wit, that we should infer to the best explanation, provided certain additional conditions are met. The first experiment studies the relation between the quality of an explanation and people's willingness to infer that explanation when only one candidate explanation is given. The second experiment presents participants always with two explanations and investigates the effect of the presence of an alternative on the participants' willingness to infer the target explanation. Although Experiments 1 and 2 manipulate explanation quality and willingness to infer to the best explanation between participants, Experiment 3 manipulates those measures within participants, thereby allowing to study the influence of explanatory considerations on inference at the individual level. The third experiment also studies the connection between explanation quality, willingness to infer, and metacognitive confidence in the decision to infer. The main conclusions that can be drawn from these experiments are that (a) the quality of an explanation is a good predictor of people's willingness to accept that explanation, and a better predictor than the prior probability of the explanation, and (b) if more than one possible explanation is given, people are the less willing to infer the best explanation the better they deem the second-best explanation.