The Pitfalls of Familiarity

Linda is a 31-year old single woman. She is outspoken and very bright. She majored in philosophy, and as a student, she was deeply concerned with discrimination and social justice issues. She never missed an opportunity to participate in anti-nuclear energy demonstrations. Which one of these statements is more probable? <ol> <li>Linda is a bank teller</li> <li>Linda is a bank teller and is active in the feminist movement</li> </ol> If you answered 2, congratulations, you’re in the majority (~85%)! Except that it’s the wrong answer. Assume that the probability of Linda being a bank teller P(A) is 0.5, and the probability of her being active in the feminist movement P(B) is 0.8. To know the probability of those two events happening together P(C), we would need to multiply P(A) and P(B): P(C) = P(A) × P(B) = 0.8 × 0.5 = 0.4 As we can see, P(C) (0.4) is actually lower lower than both P(A) and P(B). So, the probability of Event 2 is lower than the probability of Event 1. We could even take this to the extreme, say both events have a probability of 0.99. The product of 0.99×0.99 is 0.9801, still lower than 0.99. The above question is known as the Linda Problem, first devised by Amos Tversky and Daniel Kahneman in the 1980s to demonstrate the conjunction fallacy. <a href="https://yohanestheda.medium.com/the-pitfalls-of-familiarity-14123c09f20a">Website</a>