Four cards, two numbers, two colors, and a statement you need to verify. Logic puzzles often hide traps, and the Four Cards of Wason is no exception. The real question, though, is whether the trap comes from the puzzle itself or from our own brain. Chances are that once you finish reading the explanation, you'll want to click an answer right away, but the only advice I can give you is... don't. There's something off in the path.
The Exercise
The exercise starts with four cards. The first shows the odd number 5, the second the even number 8, the third is blue, and the fourth is green. The task is to check the following statement: "If a card shows an even number on one of its sides, then its opposite side is blue" However, what the exercise really wants is for you to find the most efficient way to verify that statement. The most thorough approach would be to flip all the cards at once, but that's not allowed here. If you know a bit about programming, you'll recognize this as a classic 'if-then' statement—or, more formally, a "conditional statement" If one side has an even number, the other side must be blue. The video is interactive: it invites you to click on the answer you think is correct, but first you need to enable annotations.
https://www.youtube.com/embed/qNBzwwLiOUcThe Author and the Confirmation Bias
I admit I got it wrong on my first try. A blend of fatigue, lack of sleep, back pain, a cat landing on my head (yes, that happened), and a rookie mistake confusing even and odd led me to click anywhere. Now, where does this exercise come from? It was created by English psychologist Peter Cathcart Wason in 1966. Wason was a pioneer in the psychology of reasoning, and through it he explained why people make consistent errors in logical tasks that are, frankly, not that hard to solve. Wason is also credited with the "confirmation bias"—the tendency to favor solutions or answers that align with our beliefs, even when they are completely wrong. Sounds a bit like politics, doesn't it?
https://www.youtube.com/embed/D0jWfoRWWJoThe Answer
To make a long story short, the answer to the Four Cards of Wason puzzle is to flip over the card with the 8 and the green card. If you turn over the 8 and find a color other than blue, the statement is false. Similarly, if you flip the green card and its other side is not an odd number, the statement is false. Over the decades, the puzzle has seen dozens of variations, and this is just one. Have you seen it in another format? Leave a comment!
