One rule, four cards, and a trap almost everyone falls into.
Here is the most famous demonstration of the way our minds cut corners. It looks like an easy logic question. Fewer than one person in ten gets it right.
Every card has a letter on one side and a number on the other. The rule to test: if a card has a vowel on one side, it has an even number on the other.
Four cards are on the table, showing what you see below. Which cards must you turn over — and only those — to find out whether the rule is being broken? Tap the ones you would flip, then check.