The role of probabilistic processes in deductive and inductive reasoning

Deductive and inductive reasoning are two fundamental forms of human inference. Deductive reasoning concerns whether a conclusion necessarily follows from its premises, whereas inductive reasoning concerns whether a conclusion is plausible given the available evidence. A key question in reasoning research is whether these two forms of reasoning rely on distinct cognitive processes or on a shared mechanism. In this talk, I present two experiments examining how logical structure and semantic cues influence reasoning judgments under deductive and inductive instructions. Participants evaluated arguments that varied in logical validity and in semantic properties of the premises, such as their diversity or specificity. The results show strong and consistent sensitivity to logical validity across both instruction types, suggesting that logical structure influences judgments even when people evaluate plausibility. In contrast, semantic cues had smaller and less consistent effects. These findings challenge strong dual-process accounts that assume a clear separation between deductive and inductive reasoning and instead support the view that both deduction and induction operate through the integration of multiple cues.