A few years ago, I saw a video of linguist-psychologist Steven Pinker discussing an experiment designed by Peter Wason in 1966. Unfortunately, I can’t find that video anymore, but Pinker discusses it further in his book How the Mind Works.

The experiment is called the “selection task”, but don’t go looking it up just yet: I have recreated it here for you to try.

Part 1

Four cards are laid out in front of you. You may assume that every card has a colour on one side and a number on the other.

Red Black 3 8

You are told that:

Every red card has an odd number on the other side.

What card(s) do you have to turn over to verify this statement is correct?

Part 2

Four cards are laid out in front of you. You may assume that every card has a drink on one side and an age on the other.

They represent patrons in a pub and the respective beverages with which they have been furnished.

Wine Milk 32 14

You are told that:

Every alcoholic drink has an age 18 or over on the other side.

What card(s) do you have to turn over to verify this statement is correct?

Review

For part 1, we would need to check only the red card and the 8.

The key is that we must turn over any cards which may allow us to prove the rule (every red card has an odd number on the other side) false.

  • We do not need to check the 3. Whether the reverse is red or blue, the card abides by the rule.
  • We do not need to check the blue card. Whether the reverse is even or odd, the card abides by the rule.
  • We must check the 8. If the reverse is red, the card breaks the rule.
  • We must check the red. If the reverse is even, the card breaks the rule.

It is common to misunderstand the logic behind this, and it is remarkably usual for people to turn over the 3 in order to check that it has a red back.

For part 2, the logic is identical. However this time, there is a social understanding interwoven into the example.

  • We do not need to check the 32. Someone who is 32 can drink what they like.
  • We do not need to check the milk. A person of any age may drink milk.
  • We must check the 14. If they are drinking alcohol, they are breaking the rule.
  • We must check the wine. If the they are under 18, they are breaking the rule.

Many people will get this puzzle correct very quickly.

Did you struggle more with the first part than with the second? That’s the expected outcome, and I find it interesting that in general our brains are really good at logic when it concerns real-life scenarios.

I think this must be why analogies are so useful for learning abstract concepts. It’s like we are tricking our brains into solving complex puzzles. And it makes total sense: we have spent our whole lives learning about the real world and how it functions, and not very much time at all learning about logic.

It is great if we can use that intuition to help us solve more abstract puzzles, but at the same time we have to be careful. We may end up drawing analogies with real life scenarios which don’t quite hold, and inadvertently end up coming to an incorrect conclusion. For example, had the rule in part 2 been “Every card with an age 18 or over has an alcoholic drink on the other side”, I suspect more people may get the answer wrong…

1st February 2026: I’ve removed the interactive part of this as I move to a static site.