Wason Selection Task Exercise

On the table in front of you are a bunch of cards. Some of them show a "4", some a "7", others show "A" and still others show a "D". You believe that each card has either a "4" or a "7" on one side and an "A" or a "D" on the other.  You need to determine whether the following rule is true: "If a card has an "A" on one side, then it has a "4" on the other. 

Why is it wrong to turn over just the "A" cards and the "4" cards?  Try to explain this on your own before reading further.

O.k. You can read further.

Well, it is correct to turn over the A cards, since if it's true that if a card has an "A" on one side, it has a "4" on the other, then all cards with an "A" on one side should have a "4" on the other. But we don't have to look at the cards with a "4", since the rule does not say that if a card has a "4" on one side then it has an "A" on the other. So turning over the cards showing a "4" is irrelevant.  But suppose a card shows a non-4, i.e. a "7"? We need to turn over those cards to make sure that those cards are non-"A"s, that is, that they are "D"s. So the correct result is that we need to look at the "A"s and the "7"s.

This task is called the Wason Selection Task, named after a cognitive psychologist who studied how people reason. Wason found that most people make the wrong inference in this task. So most people do not reason logically when it comes to reasoning about conditionals, propositions of the form "If A then B."  If you don't fully understand the reasoning at work here, don't worry! You're just starting to study logic. In a few weeks you'll have a much deeper appreciation of the logic of conditionals, and you'll be able to explain what's going on here quite easily.