Steven Pinker -- How the Mind Works - Hampshire High Italian ...

336 | HOW THE MIND WORKSedge. In the restaurant story, for example, the links of inference alternatebetween knowledge of menus and applications of logic.Some areas of knowledge have their own inference rules that caneither reinforce or work at cross-purposes with the rules of logic. Afamous example comes from the psychologist Peter Wason. Wason wasinspired by the philosopher Karl Popper's ideal of scientific reasoning: ahypothesis is accepted if attempts to falsify it fail. Wason wanted to seehow ordinary people do at falsifying hypotheses. He told them that a setof cards had letters on one side and numbers on the other, and askedthem to test the rule "If a card has a D on one side, it has a 3 on theother," a simple P-implies-Q statement. The subjects were shown fourcards and were asked which ones they would have to turn over to see ifthe rule was true. Try it:Most people choose either the D card or the D card and the 3 card. Thecorrect answer is D and 7. "P implies Q" is false only if P is true and Q isfalse. The 3 card is irrelevant; the rule said that D's have 3's, not that 3'shave D's. The 7 card is crucial; if it had a D on the other side, the rulewould be dead. Only about five to ten percent of the people who aregiven the test select the right cards. Even people who have taken logiccourses get it wrong. (Incidentally, it's not that people interpret "If Dthen 3" as "If D then 3 and vice versa." If they did interpret it that waybut otherwise behaved like logicians, they would turn overall four cards.)Dire implications were seen. John Q. Public was irrational, unscientific,prone to confirming his prejudices rather than seeking evidence thatcould falsify them.But when the arid numbers and letters are replaced with real-worldevents, sometimes—though only sometimes—people turn into logicians.You are a bouncer in a bar, and are enforcing the rule "If a person isdrinking beer, he must be eighteen or older." You may check what peopleare drinking or how old they are. Which do you have to check: a beerdrinker, a Coke drinker, a twenty-five-year-old, a sixteen-year-old? Mostpeople correctly select the beer drinker and the sixteen-year-old. Butmere concreteness is not enough. The rule "If a person eats hot chilipeppers, then he drinks cold beer" is no easier to falsify than the D's and3's.Leda Cosmides discovered that people get the answer right when the