A piano. The word piano has five letters, and the scale on the piano is A through G, seven letters. The piano keys don’t have locks and playing piano requires you to keep time (but with a metronome, not a clock).
Four cards are placed in front of you on the table, each with a number on one side and a color on the other. The visible cards show 3, 8, red and brown. Which cards should you turn over in order to test the truth of the statement that if a card shows an even number on one face, then its opposite face is red?
You’d need to turn over only the 8 and brown card. Only a card with an even number on one face and which is not red on the other face can invalidate the stated rule. If you turn over the 3 card and it’s not red, it doesn’t invalidate the rule, nor does turning over the red card and finding it has the label 3.
This test was devised by Peter Cathcart Wason and is known as the Wason selection task. Less than 10% of test subjects got it correct in two separate studies.
Add a diagonal line on the top left of the first plus sign to convert + into a 4. You could also put a slash through the equal sign to make ≠ (not equal) but that’s not as cool.
