Conjunction Fallacy Chris is 35. He studied social philosophy and has had an interest in developing countries since he was a teenager. After graduation, he worked for two years with the Red Cross in West Africa and then for three years in its Geneva headquarters, where he rose to head of the African aid department. He then completed an MBA, writing his thesis on corporate social responsibility. What is more likely? A) Chris works for a major bank or B) Chris works for a major bank, where he runs its Third World foundation. A or B? Most people will opt for B. Unfortunately, it’s the wrong answer. Option B does not only say that Chris works for a major bank, but also that an additional condition has been met. Employees who work specifically within a bank’s Third World foundation comprise a tiny subset of bankers. Therefore, option A is much more likely. The conjunction fallacy is at play when such a subset seems larger than the entire set – which by definition cannot be the case. Nobel laureate Daniel Kahneman and Amos Tversky have studied this extensively. We are easy prey for the conjunction fallacy because we have an innate attraction to ‘harmonious’ or ‘plausible’ stories. The more convincingly, impressively or vividly Chris the aid worker is portrayed, the greater the risk of false reasoning. If I had put it a different way, you would have recognised the extra details as overly specific: for example ‘Chris is 35. What is more likely? A) Chris works for a bank or B) Chris works for a bank in New York, where his office is on the twenty-fourth floor, overlooking Central Park.’ Here’s another example: What is more likely? A) ‘Seattle airport is closed. Flights are cancelled.’ B) ‘Seattle airport is closed due to bad weather. Flights are cancelled.’ A or B? This time, you have it: A is more likely since B implies that an additional condition has been met, namely bad weather. . . . The difference between intuitive and conscious thinking is much more significant. With important decisions, remember that, at the intuitive level, we have a soft spot for plausible stories. Therefore, be on the lookout for convenient details and happy endings. Remember: if an additional condition has to be met, no matter how plausible it sounds, it will become less, not more, likely. - The Art of Thinking Clearly, Rolf Dobelli
Posted on: Wed, 03 Sep 2014 08:15:35 +0000
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