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Wason's Four-Card Task

Difficulty: * * *   (explanation of difficulty)

This is a test devised in 1966 by Peter Wason, who used it to study people's propositional reasoning. It appears to be quite simple, but only 5% of the partipants in the initial study got the correct answer. Can you perform the task correctly?

Instructions: Four cards are depicted below. Each of them has a letter on one side and a digit on the other. Given the rule "If a card has a vowel on one side, then it has an even number on the other side", which cards would you need to turn over to allow you to determine whether the rule is true? Select the cards that you would need to turn over by clicking on each of them (if you change your mind, click on them again to unselect them). When done, select the "Check Answer" button to check your answer.
A D 4 7

Answer: The correct answer is to select the "A" card and the "7" card. You would need to check the "A" card because, if it had an odd number on the other side, the rule would be false. You would need to check the "7" card because, if it had a vowel on the opposite side, the rule would be false. Most people select the "4" card, but you do not need to check that, because, regardless of whether it has a vowel or a consonant on the other side, it would not show the rule to be false.

You can read more about Wason's Four-Card Task on our sister site, Math Lair.