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)
Use of logic 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). One experiment revolving around the Wason four card problem found many influences on people's selection in this task experiment that were not based on logic. The non-logical inferences made by the participants from this experiment demonstrate the possibility and structure of extra-logical reasoning mechanisms. Alternatively, one might solve the problem by using another reference to
zeroth-order logic. In
classical propositional logic, the
material conditional is false if and only if its antecedent is true and its consequent is false. As an implication of this, two cases need to be inspected in the selection task to check whether we are dealing with a false conditional: • The case in which the antecedent is true (the even card), to examine whether the consequent is false (the opposite face is
not blue). • The case in which the consequent is false (the red card), to study whether the antecedent is true (the opposite face is even). ==Explanations of performance on the task==