Can you solve the Wason Selection Test?

This puzzle from the 1960s, designed to test our logic, is still as hard as ever. In fact, nine out of 10 people get it wrong.

If a card shows an even number on one face, then its opposite face is blue. Which cards must you turn over in order to test the truth of his proposition?

Supposedly, it’s an easy proposition. But the creator, English psychologist Peter Wason, called it “deceptively easy” before he passed away in 2003. Since the test was devised, researchers have been analyzing it and supporting the original thesis that people usually fail because they misinterpret the word “if.”

It goes like this: You are shown four cards — an odd number; an even number; a blue color and a green color. Then you are instructed as follows: If a card shows an even number on one face, then its opposite face is blue. Which cards must you turn over in order to test the truth of his proposition, without turning over any unnecessary cards?

See it in action here:

You’re supposed to lift: 1) the even number to make sure it’s back is blue and 2) the green color to make sure it’s back is an odd number.

This lack of such seemingly obvious logic has been looked at many times since the 1960s, including landmark studies in 1982, 1989 and 2011. Among the follow-up findings was a theory that younger people are more likely to solve an if-then puzzle when the premise is less abstract than just numbers and colors. The example involves testing for underage drinkers: “if” there’s a drink in their hand, “then” they’re older than 21.

But there are still two distinctive camps — those who believe in System 1 (the fast answer) and System 2 (the slow one). Nobel Prize-winning psychologist Daniel Kahneman said in his book Thinking, Fast and Slow that the first camp relies on what is named in the clue, while the second camp allows the first to guide its decisions.

To this day, both sides argue their theories. But the experimental output of the question still remains open to your own interpretation. So, which one are you in?

## Another brain teaser

Here’s one of those viral math problems you may have seen in your Facebook feed. This one’s from Math Meeting, and has led to a lot of arguments. Why don’t you give it a shot, then we’ll go over the answer here.