Wason selection task
A four-card logic puzzle most people fail — until it is framed as cheating.
What it means
The Wason selection task asks people which cards must be turned over to test a conditional rule of the form 'if P then Q,' and most choose the cards matching the items named in the rule rather than the logically required P and not-Q. The dominant error is failing to seek potential falsifying evidence, a laboratory signature of confirmation-seeking and of matching bias. Strikingly, performance leaps when the same abstract structure is dressed as a social contract or permission rule ('if you drink alcohol, you must be over 18'), which some interpret as evidence for evolved cheater-detection mechanisms and others for the role of familiar content and pragmatic cues. The task became a touchstone in the rationality debate and in dual-process theorizing about when logic overrides intuition. It crisply demonstrates that human reasoning is content-sensitive, not content-neutral.
Examples
Given cards showing A, K, 4, 7 and the rule 'if a card has a vowel on one side it has an even number on the other,' most people pick A and 4, but the correct choice is A and 7.
Testing 'if a customer gets the discount, they must have a loyalty card,' staff know to check discounted receipts and card-less customers — the same logic they miss with letters and numbers.
A manager convinced that 'remote workers miss deadlines' reviews only the remote team's late projects, never the office staff's — checking the cases that could disprove the rule is the step people skip.
First described in Peter Wason (1966); social-contract version, Cosmides (1989).