The Undoing Project: A Friendship That Changed Our Minds

Though Danny and Amos had been at the University of Michigan at the same time, their paths did not cross until they were both working at Hebrew University. Amos came into Danny’s class and guest lectured on some of the research led by Ward Edwards at his lab at the University of Michigan. Edwards was testing a theory on whether people more or less acted as if they knew Bayes’s theorem, a formula that calculated probabilities and odds when people were given new information, such as pulling either a red or white poker chip out of a bag. After completing a math textbook called Foundations of Measurement, Amos was looking for a new line of inquiry. As he explained Edwards’s research in Danny’s class, the students in the room were surprised. Even though Danny and Amos had already established themselves as the stars of the psychology department, the two had never interacted until that guest lecture.

The moment proved to be underwhelming. Danny was astounded by how unimpressive Edwards’s research was, including the premise that anchored the work. As Lewis writes, “to Danny, the experiment that Amos described sounded incredibly stupid. After a person has pulled a red chip out of a bag, he is more likely than before to think the bag to be the one whose chips are mostly red: Well, duh” (147).