Hypothesis Testing Strategy in Wason’s 2-4-6 Reasoning Task

We examined theories of hypothesis testing strategy in Wason’s 2-4-6 task. Twenty-one under graduate students were given single trials that featured a hypothesis and an example conforming to the hypothesis, and they received “yes/ no” feedback as to whether the example conformed to a hidden rule. We included three conditions: mere confirmation, inconsistency, and consistency. “Yes” feedback was presented in the former two conditions. Feedback negativity, a negative-event-sensitive event-related potential, was enhanced in inconsistency trials that featured falsification of contrary hypotheses, in comparison with mere confirmation trials. This result is consistent with the “iterative counterfactual strategy” (Oaksford & Chater, 1994) account but not with the “positive test heuristic” (Klayman & Ha, 1987), in that the latter is unable to qualitatively discriminate “yes” feedback trials.