Cheater Detector (quote)
Some areas of knowledge have their own inference rules that can either reinforce or work at cross-purposes with the rules of logic. A famous example comes from the psychologist Peter Wason. Wason was inspired by the philosopher Karl Popper's ideal of scientific reasoning: a hypothesis is accepted if attempts to falsify it fail. Wason wanted to see how ordinary people do at falsifying hypotheses. He told them that a set of cards had letters on one side and numbers on the other, and asked them to test the rule "If a card has a D on one side, it has a 3 on the other," a simple P-implies-Q statement. The subjects were shown four cards and were asked which ones they would have to turn over to see if the rule was true. Try it: Most people choose either the D card or the D card and the 3 card. The correct answer is D and 7. "P implies Q" is false only if P is true and Q is false. The 3 card is irrelevant; the rule ...