Four Cards

Four cards are placed in front of you on the table, each with a number on one side and a color on the other. The visible cards show 3, 8, red and brown. Which cards should you turn over in order to test the truth of the statement that if a card shows an even number on one face, then its opposite face is red?

You’d need to turn over only the 8 and brown card. Only a card with an even number on one face and which is not red on the other face can invalidate the stated rule. If you turn over the 3 card and it’s not red, it doesn’t invalidate the rule, nor does turning over the red card and finding it has the label 3.

This test was devised by Peter Cathcart Wason and is known as the Wason selection task. Less than 10% of test subjects got it correct in two separate studies.

Posted in Brain Teasers

3 Comments on "Four Cards"

cassidy says
November 24, 2015 @ 02:13

the brown card because it would either contain a odd or even number when turned over

Gabby says
June 4, 2016 @ 22:50

The only way to know the truth of the statement is to turn all of them over. Any card could disprove the statement.

Simon says
August 3, 2016 @ 10:52

@Gabby: No, you only need to turn over the 8 and the brown one. The question is only an implication in one direction, from even->red. If a card is odd and red it doesnt disprove the statement

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