The Wason Card Problem
is a well known test in the study of deductive reasoning.
You are given 4 cards, two face up and two face down; say, 3,8, Red, Brown, and asked which card(s) must be turned over in order to test the truth of the proposition that if a card shows an even number on one face, then its opposite face is Red?
Apparently only a small percentage of those tested give the 'correct' solution - although the 'great majority of subjects agree with the logic of the solution, once it is explained to them'.
The 'correct' solution is given in the article, but it is worth attempting to solve it first, if you are not already familiar with it.
Question: Why is the 'correct' solution in fact questionable?
I think that when it's usually presented, it specifies that one side has a number and the other side a solid color, such as on an ordinary playing card, and the "correct" solution is in fact correct: The card showing 8 and the one showing brown have to be examined, to test the positive and the contrapositive.
If presented without the prequalifier that one is assured that one side always has a number and the other only a color, then one must check all three cards that do not show red, as even the 3 might then have an even number on the other side.
Posted by Charlie
on 2015-06-01 12:35:04