Peter Cathcart Wason proposed a form of the following task, which is failed by 90 percent of people who attempt it (though users of this website have a better track record). Try the task yourself, and see how others responded. Then read the answer and explanation, and try a real-life version.

There are four cards, each of which has a number on one side and a color on the other. The cards lie on a table with the following faces showing: 3, 8, green, blue. The task is to identify which cards need to be turned over in order to test the truth of the following proposition: “If one of these cards has an even number on one side then its other side is green.” Which cards would you turn over, without turning over any cards unnecessarily?

The correct answer is that you must turn over only the 8 card and the blue card. Here is an explanation for each of the cards:

• 3 card: does not need to be turned over, because it is not even, so it cannot trigger the stated proposition
• 8 card: even, so it must be turned over, because if the other side is not green, then the proposition is not true
• green card: many people choose this card, but it does not need to be turned over, because if the other side is odd, then the proposition is not tested, and if the other side is even, that is consistent with the proposition, but it does not prove or disprove the truth of the proposition
• blue card: does need to be turned over, because if the other side is even, then the proposition is not true

A Real-Life Scenario

The Wason task is difficult in part because it tests abstract logical reasoning. Many people perform better on a similar test based on a real-life scenario. Say that you work in a bar, stopping underage people from drinking. Your job is to test this rule: “If someone is drinking alcohol, then that person must be age 18 or older.” From where you are standing, you can observe four people: a person drinking soda (you can’t see how old they are); a person drinking beer (you can’t see how old they are); a 30-year-old person (you can’t see what they’re drinking) and a 16-year-old person (you can’t see what they’re drinking). Which of these four items must be checked in order to make sure the rule is being followed? For this task, your “cards” would look like this:

Logically, this task is identical to the first one. However, most people find it easier to figure out which cards need to be checked: the beer and the teenager.

## 7 thoughts on “The Wason Selection Task”

1. Anonymous says:

hate you

1. Another victim! Bwahahaha. 🙂

1. Anonymous says:

If you turn over the blue it doesn’t prove [anything]. There’s no accurate way to tell if even must be green. Or else the question is poorly put

1. You are right that turning over the blue card cannot prove the statement, but it might disprove it. The task is to prove whether this statement is true or false: “If one of these cards has an even number on one side then its other side is green.” You know each card has a color on one side and a number on the other. With the blue card, imagine if the number 4 was on the other side. That would disprove the statement! So you have to check.

2. I liked it. I guessed the wrong answer immediately, before rereading the question and realising that the Green card didn’t need to be turned over. It was fun.

1. I like your attitude! 🙂

3. Vish Vis says:

GATE 2017 GENERAL APTITUDE questions set by IIT ROORKEE is taken from here i think.. just see question 58 civil engg. set2..and ece set2 question 58. here is the link to question papers http://www.gate.iitr.ernet.in/?page_id=485