The Tipping Point: How Little Things Can Make a Big Difference

by Malcolm Gladwell

Consider the following brain teaser. Suppose I give you four cards labeled with the letters A and D and the numerals 3 and 6. The rule of the game is that a card with a vowel on it always has an even number on the other side. Which of the cards would you have to turn over to prove this rule to be true? The answer is two: the A card and the three card. The overwhelming majority of people given this test, though, don’t get it right. They tend to answer just the A card, or the A and the six. It’s a hard question. But now let me pose another question. Suppose four people are drinking in a bar. One is drinking Coke. One is sixteen. One is drinking beer and one is twenty-five. Given the rule that no one under twenty-one is allowed to drink beer, which of those people’s IDs do we have to check to make sure the law is being observed? Now the answer is easy. In fact, I’m sure that almost everyone will get it right: the beer drinker and the sixteen-year-old. But, as the psychologist Leda Cosmides (who dreamt up this example) points out, it is exactly the same puzzle as the A, D, 3, and 6 puzzle. The difference is that it is framed in a way that makes it about people, instead of about numbers, and as human beings we are a lot more sophisticated about each other than we are about the abstract world.