IN HIS 2012 bestseller “Thinking, Fast and Slow,” a tour de force of popular science, world-renowned Israeli psychologist Daniel Kahneman laid bare our cognitive foibles.Our minds, he explained, frequently play weird tricks on us, but we believe ourselves to be firmly in control.The book, too, played a trick of sorts by having had a dead man partly in control of its creation. Kahneman, 82, dedicated his magnum opus to his late friend and long-time academic collaborator, Amos Tversky, with whom he claimed to have possessed “a shared mind that was superior to our individual minds.” Absent his friend, Kahneman could never have done most of his groundbreaking research for “Thinking, Fast and Slow.”Tversky, who coauthored numerous influential academic papers and scientific articles with Kahneman over almost two decades before his death in 1996, duly looms large in the book. There he is, page after page, usually in the recurring phrase “Amos and I,” thinking, brainstorming, opining, theorizing and analyzing with Kahneman. In the dog-eat-dog world of academe, riven by jealousies and dominated by self-serving ambitions, the two Israeli scientists were a remarkable pair: kindred spirits and fine minds devoted as much to their science as to each other.Their storied friendship and their celebrated collaborative scholarship deserve fleshing out, and the American writer Michael Lewis does just that in “The Undoing Project.”Lewis is the author of the 2003 bestseller “Moneyball,” in which he chronicled a middling US baseball team’s quest to become more competitive by relying not on traditional expert opinions but on cold-headed statistical analysis. “The Undoing Project,” the author notes, was inspired by a psychologist’s critique of “Moneyball,” which first brought the Israel duo’s insights into human judgments and decision-making to his attention.THE RESULT is an informative, occasionally arresting but vexingly discursive book, which can give you severe whiplash as it frequently bounds from topic to topic with nary a dollop of narrative or thematic glue. The first chapter kicks off with a lengthy exposition on the vagaries of recruiting new talents for NBA teams. Neither Kahneman nor Tversky makes even a cameo.Then, in the second chapter, we suddenly encounter Kahneman doing his best, as a precocious Jewish teenager, to elude capture in Nazi-occupied France. After the war, Kahneman immigrates to Israel, where he studies at the Hebrew University in Jerusalem, which is partly and temporarily housed inside a monastery owing to the Jordanian occupation of the city’s eastern half. He cuts his teeth under charismatic teachers like the temperamental intellectual Yeshayahu Leibowitz.There’s not one more word about basketball, or any other sport, for the rest of the book. Presumably, Lewis, or his publisher, felt that his American readers wouldn’t care much about two Israeli psychologists unless they could be seen to have something to contribute to a better understanding of an all-American pursuit like basketball.Be that as it may, in the third chapter, we leave Kahneman and meet a young Tversky, a whip-smart, charismatic maverick from Haifa who rises to command units of paratroopers and infantrymen, fights in the wars of 1956 and 1967, and receives an award for bravery from Moshe Dayan. Like Kahneman, Tversky, too, is something of a prodigy and is naturally drawn to the field of psychology, which is still a nascent discipline in Israeli academia.Separately, Kahneman and Tversky are both creative and original thinkers; together, they will become a formidable team.Clearly enamored of his subjects, whom he familiarly calls Danny and Amos throughout, Lewis often winds up tottering precariously on the verge of hagiography. At times he topples headlong into it. Tversky, he reports breathlessly, was “the last to go to bed, the life of every party, the light to which all butterflies flew, and the freest, happiest, and most interesting person anyone knew.”Good to know.Just by wearing a suit and tie to work at Hebrew University, where he becomes an assistant professor, Tversky causes a sensation in the Spartan, no-nonsense and caustically irreverent social milieu of the 1960s. Good to know that, too. But we’re a third way into the book, and Amos and Danny have yet to meet or so much as be mentioned in the same breath.Meet they finally do, in 1969 and Chapter 5. In short order, Tversky becomes yin to Kahneman’s yang, the ebullient, gungho extrovert complementing the reserved, brooding introvert, as the two set about tackling a series of daunting problems in psychology. “Both wanted to search for simple, powerful truths,” Lewis writes.IN THOSE days, most of psychology wasn’t (as it still largely isn’t) a proper science with empirically sound, quantifiable properties underlying the various grand hypotheses about the animating forces of human behavior. Instead, it was like a form of art, a field of creative intuition where the ideas of prominent psychologists became received wisdom among their followers.Yet both Kahneman and Tversky, each a polymath of sorts in his own way, were fascinated by it – not so much by the academic discipline itself as the quest that it purported to embody: the search for key insights into why we think and behave the way we do.Kahneman was influenced by experimental Gestalt psychology, a field originated and dominated by German Jews in the 1920s and which holds that our perceptions of the world are mediated by our pattern-seeking tendencies, which we often employ to impose meanings arbitrarily, even when there are none. As one of Israel’s first army psychologists, Kahneman learned at firsthand that what may seem like sound judgments of people’s potentials based on their apparent temperaments and abilities can be fraught with errors and misconceptions. Our first impressions and initial expectations of others can badly skew our judgments of them.To reduce such mistakes, he devised new personality assessment techniques for the IDF, which are still in use.Kahneman, whom Lewis aptly dubs “a spectacularly original connoisseur of human error,” set out to find a method for ameliorating the impact of flawed personal opinions on decisions – be it in the military, politics, business or medicine. The key, he thought, was to eliminate our innate biases by reining in our “gut feelings.” Independently, Tversky arrived at similar conclusions about the flaws in human decision-making. People, he realized, choose between two or more options based not only on the various features of each but also on which of those features they regard as more relevant whenever they happen to make their choice. In other words, context can greatly influence the outcome of their choice. Tversky was also expert at math and statistics, which would soon help anchor the two’s formative insights in quantifiable foundations.AS ONE of their first tasks, the dynamic duo proved that people, experts included, are ready to draw sweeping, and frequently wrong, conclusions from a few random or select facts or observations. This may not seem like a revolutionary insight but it went against the prevailing idea at the time that credited people with being intuitive, natural- born statisticians, who could somehow divine hard truths from a few bits of data. Innate probabilistic reasoning, the two Israeli experts showed, is not one of our strengths as a species. That’s why computerized algorithms, not being prone to the human mind’s frequent erroneous judgments, can do the job of analyzing, diagnosing and predicting far better than flesh-and-blood experts.Through a series of similar experiments, Kahneman and Tversky documented that we understand the world by the help of instinctive habits of mind that serve us well in some situations but let us badly down in others.As a result, we often err in our judgments but rarely realize it. We use mental shortcuts, or “heuristics” in academic parlance, to evaluate probabilities and make judgments accordingly, but we aren’t very good at it.We’re slaves to a whole host of built-in cognitive biases – confirmation bias, hindsight bias, illusory correlation bias. They carried on for years and years, tackling problems, slaying sacred cows of utility theory and decision analysis, and prying ever further into the whims of human folly.All the while they remained fast friends.“They’d become a single mind, creating ideas about why people did what they did,” Lewis writes, echoing Kahneman’s own assessment of their relationship.SOME OF the two Israelis’ findings about human psychology proved seminal, such as their insight that people approach risks differently when they’re faced with the prospect of a certain gain or a certain loss. They act more circumspectly in the former case but are more willing to gamble in the latter so as to avoid incurring a loss. The reason: “our greater sensitivity to negative rather than positive changes,” as they put it. “For most people,” they elucidated, “the happiness involved in receiving a desirable object is smaller than the unhappiness involved in losing the same object.”Likewise, we evaluate gains and losses according to our “reference point,” our subjective and transient baseline for what we see as gains and losses. If, for example, we expect a year-end bonus of $100,000 but receive only $50,000, we will likely feel cheated, even though we still have made a gain. If, on the other hand, we receive the full $100,000 but learn that everyone else at work has received $150,000, we will likely feel cheated again because our reference point will suddenly have shifted to what everyone else has got. This quirk of human nature means we can easily be coaxed into taking or avoiding risks, depending on whether we’re made to believe, through a simple reframing of context, that we’re facing a net gain or a net loss.The Israeli pair presented their new “prospect theory,” a form of value theory, to a select group of leading experts during an international conference held at a kibbutz near Jerusalem in 1975. “And so it was on a farm that a theory that would become among the most influential in the history of economics made its public debut,” Lewis observes. It would help Kahneman win the Nobel Prize in economics in 2002. Tversky was equally deserving of the honor, but by then he had died of cancer, at age 59.Other findings of theirs that Lewis relays appear less momentous. Take this one: Kahneman and Tversky prove, through a series of experiments, that people are essentially risk averse. Given a choice, say, between the certainty of receiving $400 and a 50 percent chance of receiving $1,000, most people, loath to gamble as they are, will forfeit the prospect of the larger sum and settle for $400. This will come as a surprise only to someone unfamiliar with the age-old proverb “a bird in the hand is worth two in the bush,” which has long testified to just such pecuniary prudence.Human affairs are animated by what the American psychologist Paul Meehl called “the ubiquity and recalcitrance of irrationality,” but you need not be a trained psychologist to see that. Lewis has done us a favor by documenting the long and intellectually fruitful friendship of Kahneman and Tversky while simultaneously helping popularize their insights. Ultimately, however, “The Undoing Project” is an uneven book, in turns riveting and prosaic, astute and humdrum.Regretfully, it also leaves some issues it raises unexplored. “[T]he question of whether God exists left me cold,” Kahneman, the grandson of Lithuanian rabbis, explains at one point apropos his burgeoning atheism in his youth, “But the question of why people believe God exists I found really fascinating.”We never learn what answers to that question he’s found. Too bad, because it’d be worth finding out.