The Undoing Project

Any Good Books

February 2017

The Undoing Project: A Friendship That Changed Our Minds

Michael Lewis (W.W. Norton, 2017)

    Amos Tversky and Daniel Kahneman would have had brilliant careers in psychology if they had never known each other. Amos worked in mathematical psychology, and helped write the principal reference on measurement. He was as lively and outgoing as his chosen subject was dry, and he could get to the heart of other subjects with shocking speed, able to appear the smartest physicist in a room full of them. Danny was the most interesting teacher at Hebrew University, with a seemingly limitless supply of ideas and questions about why people act the way they do. At 22, he designed an assessment system for the Israeli military which helped it make better decisions about assignments and promotions. He was cut from a different cloth personally, feeling an acute sensitivity to the opinions of others where Amos felt none. 

 

    But when they started working together, in 1969, they hit it off like peanut butter and chocolate. Both had studied at the University of Michigan before returning to Hebrew University as professors, and one day Amos came to a seminar Danny was teaching. He came to discuss some work being done at Michigan about how people judge probability; the working assumption was that people have an intuitive grasp of statistical theory, though they sometimes make mistakes in expressing it. Danny, who had taught statistics, thought that was ridiculous, and said so; he won the argument that day. 

 

    That fall, Danny and Amos renewed the argument, from the same side. They devised a test requiring statistical reasoning and tried it out at meetings of psychologists. "The resulting paper dripped with Amos's self-assurance, beginning with the title he had put on it: 'Belief in the Law of Small Numbers.'" Their point was that the Law of Large Numbers doesn't actually apply to small numbers: "Even people trained in statistics and probability theory failed to intuit how much more variable a small sample could be than the general population–and that the smaller the sample, the lower the likelihood that it would mirror the broader population." Were psychologists committing such errors in their own work? Certainly they were; if their experiments gave different results on different trials, they were far more likely to rationalize the difference away than to conclude that their samples had been too small.

    The next year, they moved on to the obvious next question:"If people did not use statistical reasoning, even when faced with a problem that could be solved with statistical reasoning, what kind of reasoning did they use?" Danny and Amos identified several rules of thumb, which they dubbed 'heuristics', that seemed to be operating when people tried to generalize from partial information. The heuristic of representativeness applies to things like choosing athletes in a draft - the front office knows what a pro basketball player 'looks like', which is a useful rule of thumb, most of the time–but it would have missed Jeremy Lin and Steph Curry. (It has since been adjusted to account for them, but who knows what else is still missing?)

    Another heuristic they called 'availability'. "Any fact or incident that was especially vivid, or recent, or common–or anything that happened to preoccupy a person–was likely to be recalled with special ease, and so be disproportionately weighted in any judgment." It's why we're always fighting the last war, and doubling our fire insurance when our neighbor's house has burned. Like other mental shortcuts, it isn't always wrong–evolution made us this way for a reason, so to speak–but when it is wrong, we have trouble catching ourselves. The previously prevalent notion that people are inherently rational has great big holes in it.

    The hundreds of days, over eight years, that Danny and Amos spent in closed rooms, arguing in Hebrew and English, shouting and laughing, gave rise to published work that made everyone think differently. Their findings were disruptive to academic psychology, not surprisingly, but also to economics, medicine, history, and sports. Their lives and academic fortunes diverged in the late seventies, and they began collaborating with other people, though probably never as fruitfully as they had together. Michael Lewis has captured a little bit of their lightning in a bottle, and you may never mistake Man for a rational animal again.