The Undoing Project

by Michael Lewis

  Danny was then helping the Israeli Air Force to train fighter pilots. He’d noticed that the instructors believed that, in teaching men to fly jets, criticism was more useful than praise. They’d explained to Danny that he only needed to see what happened after they praised a pilot for having performed especially well, or criticized him for performing especially badly. The pilot who was praised always performed worse the next time out, and the pilot who was criticized always performed better. Danny watched for a bit and then explained to them what was actually going on: The pilot who was praised because he had flown exceptionally well, like the pilot who was chastised after he had flown exceptionally badly, simply were regressing to the mean. They’d have tended to perform better (or worse) even if the teacher had said nothing at all. An illusion of the mind tricked teachers—and probably many others—into thinking that their words were less effective when they gave pleasure than when they gave pain. Statistics wasn’t just boring numbers; it contained ideas that allowed you to glimpse deep truths about human life. “Because we tend to reward others when they do well and punish them when they do badly, and because there is regression to the mean,” Danny later wrote, “it is part of the human condition that we are statistically punished for rewarding others and rewarded for punishing them.”

  The other class Danny taught was about perception: how the senses interpreted and, occasionally, misled. “Let me tell you: After two classes it was clear that this guy was brilliant,” said Avi. Danny recited long passages from the Talmud in which the rabbis described day turning to night, and night turning to day, then asked the class: What colors are these rabbis seeing at that moment, when day turns to night? What did psychology have to say about the way the rabbis saw the world around them? Then he told them about the Purkinje effect—named for the Czech physiologist who had first described it, in the early nineteenth century. Purkinje had noticed that colors that appeared brightest to the human eye in broad daylight appeared the darkest at dusk. And so, for instance, what the rabbis saw as vividly red in the morning might appear, in contrast to other colors, almost colorless in the evening. Danny seemed to have in his head not only every strange phenomenon ever uncovered by anyone but an ability to describe them all in ways that led a student to see the world just a bit differently. “And he came to class with nothing!” said Avi. “He just came in and started talking.”

  A part of Avi couldn’t quite believe the spontaneity of Danny’s performances. He wondered if perhaps Danny had memorized his lectures and was just showing off.” That suspicion was dispelled the day that Danny arrived to class and asked for help. “He came to me,” recalled Avi, “and he said, ‘Avi, my students at Hebrew University want me to give them something in writing, and I don’t have anything. I saw you writing notes. Can I have them so I have something to give them?’ . . . Everything was in his head!”

  Avi soon learned that Danny expected his students to stuff their minds in much the same way that he had. Toward the end of his class on perception, Avi was called to army reserve duty. He went to Danny to say that, sadly, he needed to leave to patrol some remote border, and so he didn’t see how he could keep up with the work and had to drop out of the class. “Danny said to me, ‘It’s okay, just learn the books.’ And I said, ‘What do you mean, just learn the books?’ And he said, ‘Take the books with you and memorize them.’” And so that’s what Avi had done. He returned to Danny’s classroom just in time for the final exam. He’d memorized the books. Before Danny handed back the exams to the students, he asked Avi to raise his hand. “I raised my hand—what did I do this time? Danny says, ‘You got 100 percent. And if someone gets a grade like this it should be said publicly.’”

  After studying with this moonlighting professor from Hebrew University, Avi made two decisions: He would himself become a psychologist. And he would study at Hebrew University. He assumed that Hebrew University must be a magical place where the professors were geniuses who inspired their students to new heights of passion for their subjects. And so for graduate school Avi went to Hebrew University. At the end of his first year, the head of Hebrew University’s Department of Psychology, surveying students, pulled Avi aside. How are your teachers? he asked.

  They’re okay, said Avi.

  Okay? said the department head. Just okay? Why are they only okay?

  I had this one teacher in Beersheba . . . , Avi started to say.

  The department head immediately sensed what had happened. Oh, he said, You’re comparing them to Danny Kahneman. You can’t do that. It’s not fair to them. There’s a category of teacher called Kahnemans. You cannot compare teachers to Kahnemans. You can say this guy is bad or good compared to others. That’s okay. But not to Kahneman.

  Inside the classroom Danny was simply a bold genius. Outside the classroom—well, Avi was surprised by the volatility of Danny’s state of mind. One day on campus, he ran into Danny and found him in a seriously dark mood—unlike anything Avi had ever seen. A student had just given him a bad review, Danny explained, and he thought that maybe he was all washed up. “He even asked me, ‘I’m still the same man, right?’” It was obvious to Avi, and to everyone else but Danny, that the student was a fool. “Danny was the best teacher at Hebrew University,” said Avi, “but it was very hard to convince him that the review didn’t matter—that he was excellent.” This was just the first of many sources of complication for Danny Kahneman: He was unusually inclined to believe the worst anyone said about him. “He was very insecure,” Avi said. “This is part of his character.”

  * * *

  To those he saw every day, Danny seemed unknowable. The picture people had in their minds of him was ever-shifting, like one of those sketches used for experiments by the Gestalt psychologists. “He was moody in the extreme,” said a former faculty colleague. “You never knew which Danny you were going to meet. He was very vulnerable. Starving for admiration and affection. Very edgy. Very impressionable. But could get easily insulted.” He smoked two packs of cigarettes a day. He’d married, and his wife had given birth to a son and a daughter, but Danny still seemed to others to live entirely through his work. “He was very much task-oriented,” said Zur Shapira, a student of Danny’s who later became a professor at New York University. “You would not say he was a happy person.” His moods put distance between Danny and other people, a bit like the distance caused by intense grief. “Women felt the urge to care for him,” says Yaffa Singer, who worked with Danny in the Israeli army’s psychology unit. “He was always in doubt,” said Dalia Etzion, who served as Danny’s teaching assistant. “I remember coming to him and he was blue. He was teaching, and he said, ‘I’m sure the students don’t like me.’ I thought: What does it matter? And it was bizarre. Because the students love him.” Another colleague said, “He was like Woody Allen, without the humor.”

  Danny’s volatility was a weakness and, less obviously, also a strength. It led him, almost inadvertently, to broaden himself. It turned out that Danny never really had to decide what kind of psychologist he would be. He could be, and would be, many different kinds of psychologists. At the same time that he was losing his faith in his ability to study personality, he was building a laboratory in which he might study vision. Danny’s lab had this bench where subjects would be immobilized in a device constructed for that purpose, with their mouths stuck in an impression of their own teeth, while Danny flashed various signals at their pupils. The only way to understand a mechanism such as the eye, he thought, was by studying the mistakes that it made. Error wasn’t merely instructive; it was the key that might unlock the deep nature of the mechanism. “How do you understand memory?” he asked. “You don’t study memory. You study forgetting.”

  In his vision lab, Danny searched for the ways people’s eyes played tricks on them. When exposed to vanishingly brief flashes of light, for example, the brightness that the eye experienced wasn’t some straightforward function of the brightness of the flash. It also depended
on the length of the flash—was in fact a product of the length of the flash and its intensity. A one-millisecond flash with an intensity of 10X was indistinguishable from a ten-millisecond flash with an intensity of X. But when flashes of light were longer than about 300 milliseconds, the brightness looked the same to people, no matter how long the flash lasted. The point of bothering to discover this was unclear, even to Danny, except that there was demand for such stuff in psychology journals, and he thought that the measuring was itself good training for him. “I was doing science,” he said. “And I was being very deliberate about what I was doing. I consciously viewed what I was doing as filling a gap in my education, something I needed to do to become a serious scientist.”

  This sort of science didn’t come naturally to him. A vision lab demanded precision, and Danny was about as precise as a desert storm. In the chaos that was his office, his secretary got so tired of being asked to help him search for his scissors that she tied them by a string to his desk chair. Even his interests were chaotic: That the same person could be mentally following schoolkids into the wilderness to ask them how many people they wanted sleeping in their tent, and sticking grown-ups’ teeth into a vise to study how their eyes worked, struck even other psychologists as odd. Personality testers were hunting for loose correlations between some trait and some behavior: tent choice and sociability, for example, or IQ and job performance. They didn’t need to be precise, and they need know nothing about people as biological organisms. Danny’s studies of the human eye felt less like psychology than ophthalmology.

  He nursed along other interests, too. He wanted to study what was known to psychologists as “perceptual defense” but to everybody else as subliminal perception. (A wave of anxiety had swept the United States in the late 1950s, thanks to a book by Vance Packard, called The Hidden Persuaders, about the power of advertising to warp people’s decisions by influencing them subconsciously. Peak craze came in New Jersey, where a market researcher claimed that he had spliced imperceptibly brief messages like “Hungry? Eat Popcorn!” and “Drink Coca-Cola” into a movie and created a surge of demand for popcorn and Coke. He later confessed he’d made it all up.) Psychologists in the late 1940s had detected—or claimed to have detected—the mind’s ability to defend itself from what it ostensibly did not want to perceive. When the experimenters flashed taboo words in front of subjects’ eyes, for instance, the subjects read them as some less troubling word. At the same time, people were also influenced by the world around them in all sorts of ways without being entirely conscious of it: Stuff got into the mind without the mind’s full awareness.

  How did these unconscious processes work? How could a person understand a word well enough to distort it, without first having perceived it in some fashion? Was there perhaps more than one mechanism inside the mind at work? Did some part of the mind perceive incoming signals, say, while another part of the mind blocked them? “I was always interested in the question: ‘Are there other ways to understand your experience?’” Danny said. “Perceptual defense was interesting because it seemed to get at unconscious life with proper experimental techniques.” Danny designed some tests himself to see if, as he suspected, people were able to learn subconsciously. He showed subjects a series of playing cards or numbers, for example, and then asked them to predict what would come next. There was a hard-to-detect sequence in the cards or the numbers. If the subjects were able to sense the sequence, they would guess the next card or number more frequently than they would by chance—and they wouldn’t know why! They’d have perceived the pattern without being aware of it. They’d have learned something subconsciously. Danny abandoned his experiments after he decided that his subjects had learned nothing.

  That was another thing colleagues and students noticed about Danny: how quickly he moved on from his enthusiasms, how easily he accepted failure. It was as if he expected it. But he wasn’t afraid of it. He’d try anything. He thought of himself as someone who enjoyed, more than most, changing his mind. “I get a sense of movement and discovery whenever I find a flaw in my thinking,” he said. His theory of himself dovetailed neatly with his moodiness. In his darker moods, he became fatalistic—and so wasn’t surprised or disturbed when he did fail. (He’d been proved right!) In his up moments he was so full of enthusiasm that he seemed to forget the possibility of failure, and would run with any new idea that came his way. “He could drive people up the wall with his volatility,” said fellow Hebrew University psychologist Maya Bar-Hillel. “Something was genius one day and crap the next, and genius the next day and crap the next.” What drove others crazy might have helped to keep Danny sane. His moods were grease for his idea factory.

  If Danny’s various intellectual pursuits had a common theme, other than his interest in them, it was hard for others to detect it. “He had no ability to see what is a waste of time and what is not,” said Dalia Etzion. “He was willing to accept anything as possibly interesting.” Suspicious of psychoanalysis (“I always thought it was a lot of mumbo jumbo”), he nevertheless accepted an invitation from the American psychoanalyst David Rapaport to spend a summer at the Austen Riggs Center in Stockbridge, Massachusetts. Each Friday morning the Austen Riggs psychoanalysts—some of the biggest names in the field—would gather to discuss a patient whom they had spent a month observing. All these experts would have by then written up their reports on the patient. After delivering their diagnoses, they would bring in the patient for an interview. One week Danny watched the psychoanalysts discuss a patient, a young woman. The night before they were meant to interview her, she committed suicide. None of the psychoanalysts—world experts who had spent a month studying the woman’s mental state—had worried that she might kill herself. None of their reports so much as hinted at the risk of suicide. “Now they all agreed, how could we have missed it?” Danny recalled. “The signs were all there! It made so much sense to them after the fact. And so little sense before the fact.” Any faint interest Danny might have had in psychoanalysis vanished. “I was aware at the time that this was very instructive,” he said. Not about the troubled patients but about the psychoanalysts—or anyone else who was in a position to revise his forecast about the outcome of some uncertain event once he had knowledge of that outcome.

  In 1965, he went to the University of Michigan for postdoctoral study with a psychologist named Gerald Blum. Blum was busy testing how powerful emotional states changed the way people handled various mental tasks. To do this he needed to induce in his subjects powerful emotional states. He did so with hypnosis. He’d first ask people to describe in detail some horrible life experience. He’d then give them a trigger to associate with the event—say, a card that read “A100.” Then he’d hypnotize them, show them the card—and, sure enough, they’d instantly start to relive their horrible experience. Then he’d see how they performed some taxing mental task: say, repeating a string of numbers. “It was weird, and I did not take to it,” said Danny—though he did learn how to hypnotize people. “I ran some sessions with our best subject—a tall, thin guy whose eyes would bulge and his face redden as he was shown the A100 card that instructed him to have the worst emotional experience of his life for a few seconds.” Once again, it wasn’t long before Danny found himself undermining the validity of the entire enterprise. “One day I asked, ‘How about we give them a choice between that and a mild electric shock?’” he recalled. He figured that anyone given a choice between reliving the worst experience of his life and mild electric shock would choose the shock. None of the patients wanted the shock: They all said they’d much rather relive the worst experience of their lives. “Blum was horrified, because he wouldn’t hurt a fly,” said Danny. “And that’s when I realized that it was a stupid game. That it cannot be the worst experience of their lives. Somebody is faking. And so I got out of that field.”

  That same year, a psychologist named Eckhard Hess wrote an article in Scientific American that caught Danny’s eye. (What didn’t?) Hess describ
ed the results of experiments he’d done measuring the dilation and constriction of the pupil in response to all sorts of stimuli. You showed a man the picture of a scantily dressed woman and his pupils expanded. The same thing happened when you showed a woman a picture of a good-looking man. On the other hand, if you showed people a picture of a shark, their pupils shrank. (Abstract art had the same effect, curiously.) If you gave people something tasty to drink, their pupils dilated; if you gave them something unpleasant (lemon juice or quinine), their pupils shrank. If you gave them tastes of five subtly different orange fizzy drinks, their pupils registered the degree of pleasure they got from each. People reacted incredibly quickly, before they were entirely conscious of which one they liked best. “The essential sensitivity of the pupil response,” wrote Hess, “suggests that it can reveal preferences in some cases in which the actual taste differences are so slight that the subject cannot even articulate them.”

  The eye might offer a window into the mind. In Blum’s hypnosis lab, with a psychologist named Jackson Beatty, whom he’d poached from Blum, Danny set out to investigate how the pupil responded when people were asked to perform various tasks that required mental effort: remember strings of digits, or distinguish sounds of different pitches. They were seeking to understand not whether the eye played tricks on the mind, but if the mind also played tricks on the eye. Or, as they put it, how “intense mental activity hinders perception.” They found that it wasn’t just emotional arousal that altered the size of the pupil: Mental effort had the same effect. There was, quite possibly, as they put it, “an antagonism between thinking and perceiving.”

  * * *

  From Michigan, Danny planned to return to a tenured job at Hebrew University. When the university delayed its decision on whether to give him tenure, he refused to return. “I was very angry,” he said. “I called and said, ‘I’m not coming back.’” Instead, in the fall of 1966, he went to Harvard. (Three years at Berkeley had persuaded him that he was smart enough to play in the big leagues.) There he heard a talk, given by a young British psychologist named Anne Treisman, that sent him in yet another direction.