Are There Two Kinds of Reasoning?

Two experiments addressed the issue of how deductive reasoning and inductive reasoning are related. According to the criterion-shift account, these two kinds of reasoning assess arguments along a common scale of strength, however there is a stricter criterion for saying an argument is deductively correct as opposed to just inductively strong. The method, adapted from Rips (2001), was to give two groups of participants the same set of written arguments but with either deduction or induction instructions. Signal detection and receiver operating characteristic analyses showed that the difference between conditions could not be explained in terms of a criterion shift. Instead, the deduction condition showed greater sensitivity to argument strength than did the induction condition. Implications for two-process and one-process accounts of reasoning, and relations to memory research, are discussed.