The Unlikely Friendship That Changed the Way We Look at Human Behavior

Michael Lewis chronicles the groundbreaking collaboration of behavioral economists Daniel Kahneman and Amos Tversky.
Illustration: Matija Medved

For the past several years, the shelves of airport bookstores from LAX to JFK have groaned under the weight of nonfiction works exploiting ideas that originated with Israeli psychologists Daniel Kahneman and the late Amos Tversky: one-syllable titles such as Nudge, Blink, and Drive; Predictably Irrational and The Power of Habit; and Kahneman’s own Thinking, Fast and Slow. In various ways, these books explain or expand on the scholars’ groundbreaking discovery that, contrary to what economists long assumed, we’re wired to make mistakes. Doctors misdiagnose illnesses, savers blow their money, and generals put troops in harm’s way because of heuristics—mental shortcuts—that don’t work.

In The Undoing Project: A Friendship That Changed Our Minds ($28.95, W.W. Norton), Michael Lewis has found a compelling way to mine this seam. He’ll likely get another movie out of it; if you saw The Blind Side, Moneyball, or The Big Short, you have Lewis to thank for the raw material. He casts Danny and Amos, as he refers to his protagonists, as mismatched men who enjoyed an intellectual bond so intense that it resembled a marriage. “What they were like, in every way but sexually, was lovers,” Lewis writes in what will probably be the book’s most quoted sentence. The Undoing Project is a history of the birth of behavioral economics, but it’s also Lewis’s testament to the power of collaboration.

Kahneman and Tversky came from different backgrounds. During World War II, Kahneman fled Paris with his family, hiding from the Nazis for a time in a chicken coop in the south of France. They moved to Israel after the war. Kahneman was messy, moody, self-doubting, and averse to conflict. Tversky, three years younger, grew up in Israel; he was neat, combative, and charismatic, physically unimpressive but brave. (Note to casting directors: Brad Pitt isn’t an obvious choice for either role.) The army decorated Tversky after he rescued a fellow soldier who fainted on top of a ticking explosive during a training exercise. From then on, he felt he had to live up to his reputation for heroism. Both men earned undergraduate degrees from the Hebrew University of Jerusalem and doctorates in the U.S.

Lewis false-starts his book with a chapter on mental mistakes by pro sports scouts, a bit that seems to have fallen out of Moneyball. His subjects don’t appear together until page 142 (of 369), when Kahneman trashes a paper that Tversky has presented at a conference. The relationship quickly becomes intense. “We just found each other more interesting than anyone else,” Kahneman tells Lewis. The two took turns as lead author on joint papers because of a mind meld that made it impossible for them to sort out who contributed what. Out of their collaboration in the 1970s came a series of landmark papers on the workings of the mind that have changed psychology, economics, and public policy. Their research inspired automatic enrollment in retirement savings programs, as well as calorie counts on menus. Marketers embrace their “prospect theory,” which describes how people value gains and losses. Irrationally, we’re happier getting two $50 vouchers than one for $100.

The friendship gradually disintegrated in the 1980s when Tversky began to get the lion’s share of public credit for their work. “I would hear their phone calls,” Tversky’s widow tells Lewis. “It was worse than a divorce.” In 1996, three days after Kahneman told Tversky they were no longer friends, Tversky called to say he’d been diagnosed with cancer and given six months to live. They reconciled before Tversky died that June. Six years later, Kahneman alone accepted the Nobel Prize for economics, which isn’t awarded posthumously.

The “undoing project” refers to an idea Kahneman proposed to Tversky as their collaboration was waning. It’s about how people mentally undo things that have happened to them, imagining what would have occurred if not for some chance event. Undoing is a process that feeds regret, frustration, and envy. Kahneman, as the surviving partner, seems to feel all those emotions about their relationship. “I hate the feeling of envy,” Kahneman told a Harvard psychiatrist in an interview, supplied to Lewis, for a book that was never published. Yet their years together were incredibly productive, and Lewis recounts with deep humanity a project that no one would ever want undone.

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