Logicians vs. Statisticians: Individual Differences in Intuitive Thinking

Classical dual-process theories of reasoning argue that intuitive judgments rely on superficial features and are largely insensitive to normative principles such as logic and probability. However, recent research on "logical intuition" challenges this view, suggesting that individuals may intuitively access logical structure. The current thesis investigates whether such intuitive responses are genuinely driven by logic or probability rules, and whether reasoning strategies moderate these effects. Two experiments were conducted to explore these questions. Experiment 1 used an instructional manipulation paradigm, presenting participants with deductive and inductive arguments under both logic and belief instructions. Experiment 2 employed a conflict detection paradigm, where participants judged the logical validity of those arguments and rated their confidence. Argument strength was manipulated using quantifiers: deductive arguments used “all” and “no”, with strength determined by logical validity, while inductive arguments used “most” and “few”, with strength determined by probabilistic plausibility. The results revealed that, across both experiments, participants’ judgments were impacted by the probabilistic strength of arguments. In Experiment 1, stronger arguments were more likely to be endorsed under belief-based instructions, including inductive arguments that were logically invalid. In Experiment 2, participants showed lower confidence in conflict arguments, including inductive ones, indicating sensitivity to probabilistic conflict. Individual differences further moderated these effects: statistical reasoners were more influenced by argument strength than counterexample reasoners in both belief-based judgments (Experiment 1) and conflict detection (Experiment 2), suggesting that reasoning strategy plays a key role in determining the extent to which people rely on probabilistic information. These findings suggest that intuitive reasoning is often probabilistic, but not universally so and individual differences in reasoning matter.<p></p>