Number of words: 392<\/p>\n\n\n\n
People aren’t good at dealing with the uncertainties or missing information in a puzzle. Here’s a neat little example that’s been tested in psychological studies and widely discussed. You’ve got four cards on the table. Each card has a letter on one side and a number on the other side. Naturally,you can only see the side that’s faceup:<\/p>\n\n\n\n
The puzzle is this: “Identify which card(s) you need to turn over in order to test the rule ‘If there is a vowel on one side of the card, there is an even number on the other side.’ “<\/p>\n\n\n\n
I’ll give you two hints (which aren’t normally given). Hint number one is that this isn’t<\/em> a trick question. There’s nothing underhanded going on. The puzzle is as simple as it looks. Hint number two is that your answer is probably going to be wrong.<\/p>\n\n\n\n Most people say either the A card or the A and 2 cards. Well, A is a vowel, and we don’t know what number is on the other side. There could be an odd number on the back of the A card. That would disprove the rule. You have to turn the A card over to test it. Fair enough.<\/p>\n\n\n\n What about the 2 card? Two is an even number, and the rule says that if there’s a vowel on one side, then there’s got to be an even number on the other side. It doesn’t say that only<\/em> vowel cards have even numbers. Say there’s a C on the other side of the 2. It wouldn’t disprove the rule. Whether there’s a vowel or consonant, it makes no difference. The 2 card is irrelevant.<\/p>\n\n\n\n So the answer’s just turn over the A card, right? Wrong. You need to turn over the 7 card too. For all we know, there could be a vowel on the other side of the 7. That would disprove the rule.<\/p>\n\n\n\n