Wason selection task

The Wason selection task (or four-card problem) is a logic puzzle devised by Peter Cathcart Wason in 1966. It is one of the most famous tasks in the study of deductive reasoning. An example of the puzzle is: You are shown a set of four cards placed on a table, each of which has a number on one side and a color on the other. The visible faces of the cards show 3, 8, blue and red. Which card(s) must you turn over in order to test that if a card shows an even number on one face, then its opposite face is blue? A response that identifies a card that need not be inverted, or that fails to identify a card that needs to be inverted, is incorrect. The original task dealt with numbers (even, odd) and letters (vowels, consonants). The test is of special interest because people have a hard time solving it in most scenarios but can usually solve it correctly in certain contexts. In particular, researchers have found that the puzzle is readily solved when the imagined context is policing a social rule. The correct response is to turn over the 8 card and the red card. The rule was "If the card shows an even number on one face, then its opposite face is blue." Only a card with both an even number on one face and something other than blue on the other face can invalidate this rule: If the 3 card is blue (or red), that doesn't violate the rule. The rule makes no claims about odd numbers. (Denying the antecedent) If the 8 card is not blue, it violates the rule. (Modus ponens) If the blue card is odd (or even), that doesn't violate the rule. The blue color is not exclusive to even numbers. (Affirming the consequent) If the red card is even, it violates the rule. (Modus tollens) The interpretation of "if" here is that of the material conditional in classical logic, so this problem can be solved by choosing the cards using modus ponens (all even cards must be checked to ensure they are blue) and modus tollens (all non-blue cards must be checked to ensure they are non-even).