Among Daniel Kahneman’s many imaginative contributions to the field of psychology is something called the “peak-end rule,” which holds that our memories of any given experience are defined not by how we felt about it moment to moment, but how we felt as it ended and how it felt at its most intense. Say you go to Italy, and the first five days are blighted by rain, but the last two are ablaze with sunshine. You are likely to remember that trip far more fondly than had it been the other way around.
Following this rule, Michael Lewis’s “The Undoing Project: A Friendship That Changed Our Minds,” which focuses on the enchanted collaboration between Dr. Kahneman and Amos Tversky, leaves a lovely afterimage. At its peak, the book combines intellectual rigor with complex portraiture. (Mr. Lewis keeps a number of single-haired paintbrushes on hand for when fine detail is required.) During its final pages, I was blinking back tears, hardly your typical reaction to a book about a pair of academic psychologists.
The reason is simple. Mr. Lewis has written one hell of a love story, and a tragic one at that. The book is particularly good at capturing the agony of the one who loves the more.
Yet passionate fans of Mr. Lewis’s should also be warned: “The Undoing Project” is less cinematic — which is to say, less plot-driven — than some of his previous books. The ideas generated by his two intense, extraordinary subjects are as much the stars of this production as the professors themselves, which means that Mr. Lewis spends stretches recapitulating and illuminating the contents of foundational academic papers; this book could stand a bit of trimming, and readers should ready themselves for tougher meat than they might be expecting to chew.
To be fair, Mr. Lewis is very aware of his quaint enthusiasms — as when he tells readers to skip ahead if they don’t care to read his footnote on Page 259, which consists almost entirely of algebraic equations. “I apologize for this,” he writes, “but it must be done.”
Mr. Lewis has always had a knack for identifying eccentrics and horde-defiers who somehow tell us a larger story, generally about an idea that violates our most basic intuition. In “Moneyball,” he gave us Billy Beane, who rejected the wisdom of traditional baseball scouts and rehabilitated the Oakland A’s through statistical reasoning. In “The Big Short,” he gave us an assortment of jittery misfits who bet against the housing market.
In “The Undoing Project,” Mr. Lewis has found the granddaddy of all stories about counterintuition, because Dr. Kahneman and Dr. Tversky did some of the most definitive research about just how majestically, fantastically unreliable our intuition can be. The biases they identified that distort our decision-making are now so well known — like our outsize aversion to loss, for instance — that we take them for granted. Together, you can safely say, these two men made possible the field of behavioral economics, which is predicated on the notion that humans do not always behave rationally.
In 2002, Sweden noticed. Dr. Kahneman was awarded the Nobel in economic science, though he’s a psychologist. You assume that Dr. Tversky would have won one, too, but the prize is reserved for the living. (He died in 1996.)
For social-science nerds, Mr. Lewis provides the back story to Dr. Kahneman and Dr. Tversky’s most famous papers. But the real drama of “The Undoing Project” — the scenes on the peak-end highlight reel — revolve around Dr. Tversky and Dr. Kahneman, both as individuals and as a creative pair.
The two men really couldn’t have been more different. True, they were both Israelis, and both saw war; they also shared a contrarian sensibility. But Dr. Kahneman arrived in Jerusalem as a shy adolescent, a refugee from France, where he’d barely survived the Nazis; Dr. Tversky was a “swaggering Sabra,” or native of Israel. Dr. Kahneman, particularly in the beginning of his career, was pessimistic, moody and profoundly insecure (“like Woody Allen, without the humor,” declares a colleague; oof). Dr. Tversky was a boffo extrovert, practically leaking self-confidence. He was also the more conspicuously dazzling to talk to. His mind was like a cow’s stomach, capable of digesting many things at once.
Yet somehow, starting in 1969, an intellectual romance bloomed between these two professors of psychology. They finished each other’s sentences and shared their own shorthand. They wrote side by side at the same typewriter. (“I cannot imagine,” the psychologist Richard Nisbett tells Mr. Lewis. “It would be like having someone else brush my teeth for me.”) In 1975, when Dr. Kahneman received a package from Dr. Tversky that he thought didn’t contain a personal note, he was crushed. Then he realized he was mistaken — there was a note there after all. “I saw the words ‘Yours, as ever’ and I had goose bumps from emotion,” he wrote in his reply.
But, like so many romances, it was fragile — and ultimately painful. As often happens in collaborations, one person, fairly or unfairly wound up getting more credit for the work, and in this case, it was Dr. Tversky. For Dr. Kahneman, this imbalance generated terrible tension and envy. That we know the details of such a close relationship, and its rocky emotional topography, is astonishing. Dr. Kahneman, 82, now at Princeton, seldom speaks to writers. But Mr. Lewis, as we know, is no an ordinary author. While Dr. Kahneman started this project as a leery participant (see the acknowledgments), he clearly softened as time went along.
And what do we learn? That envy really is corrosive. That successful marriages involve, as the psychologist Marcel Zentner discovered, “positive illusions.” That world-famous psychologists can be blind to the needs of those around them. And that even winning a Nobel doesn’t guarantee self-esteem. Late in life, Dr. Kahneman remained a rattling kettle of self-doubt.
In a remarkable note on his sources, Mr. Lewis reveals that for years he watched Dr. Kahneman agonize over his 2011 book, “Thinking, Fast and Slow,” which became both a critical and a fan favorite. “Every few months he’d be consumed with despair, and announce that he was giving up writing altogether — before he destroyed his own reputation,” Mr. Lewis writes. “To forestall his book’s publication he paid a friend to find people who might convince him not to publish it.”
Dr. Tversky never fully understood these fits of doubt. Nor did he see how he made them worse. “I needed to get away,” Dr. Kahneman said. “He possessed my mind.”
Love. It’s the least rational feeling of all.