Dr. Kahneman’s research became famous primarily for refuting the concept of “homo economicus”, “economic man”, who, since the times of Adam Smith, was considered a rational being acting in his own interest. Instead, as Dr. Kahneman discovered, people rely on intellectual shortcuts that often lead to poor decisions that go against their self-interest.

These poor decisions happen because people are “too influenced by recent events,” Dr. Kahneman once said. “In some circumstances they are too quick to reach conclusions and in others they are too slow to make changes.”

Dr. Kahneman was affiliated with Princeton University when he won the 2002 Nobel Prize in Economic Sciences “for integrating knowledge from psychological research with economic science, especially relating to human judgment and decision-making under conditions of uncertainty.” He shared the prize with Vernon L. Smith, then of George Mason University in Virginia, who pioneered the use of laboratory experiments in economics.

Dr. Kahneman was reluctant to judge a person’s ability to think through a problem. “Many people are overconfident and tend to trust their intuition too much,” he wrote in his popular 2011 book, “Thinking, Fast and Slow.” “They apparently find cognitive effort at least moderately unpleasant and avoid it as much as possible.”

Dr. Kahneman spent much of his career working with psychologist Amos Tversky, whom he believed deserved much recognition for his award-winning work. But Tversky died in 1996, and the Nobel Prize is never awarded posthumously.

Both men were atheist grandchildren of Lithuanian rabbis, and both studied and taught at the Hebrew University of Jerusalem. Their thirty-year friendship and close collaboration, described in Michael Lewis’s 2016 book “The Undoing Project,” was a study in opposites.

According to Lewis, Tversky was the soul of the party; Dr. Kahneman didn’t even go there. Tversky had a mechanical pencil on his desk and nothing else; Dr. Kahneman’s office was full of books and articles that he never finished. Still, Dr. Kahneman said, at times it seemed like we “shared the same mind.” They worked so closely together that they flipped a coin to decide whose name would get the top spot in an article or book.

Their research helped establish the field of behavioral economics, which uses psychological insights to study economic decision-making, but it also had far-reaching impact beyond the academy. He is credited with changing the way baseball scouts evaluate prospects, governments shape public policy and doctors make medical diagnoses.

Inspired in part by Dr. Kahneman and Tversky’s early work, Judgments Under Uncertainty, economist Richard Thaler and lawyer Cass Sunstein developed the concept of “libertarian paternalism.” Thaler and Sunstein’s 2008 book “Nudge” proposed how governments can encourage people to save for retirement, take care of their health and make other intelligent choices with minimal government interference.

Dr. Kahneman presented his ideas to a wide audience in the book “Thinking, Fast and Slow”, which distinguishes between two modes of thinking: System 1, in which the mind, acting quickly, is based on intuition, direct impressions and emotional reactions; and System 2, in which the mind, by slowing down, functions more rationally and analytically and is able to correct errors made by System 1.

Dr. Kahneman argued that most of the time the mind works in System 1 and draws conclusions using the System 1 toolkit: rules of thumb, cognitive biases, and anything that speeds up the judgment process.

Dr. Kahneman and Tversky conducted experiments that demonstrated various cognitive biases. For example, it was shown that many more people were willing to make a 20-minute trip to save $5 at a calculator price of $15 than to make the same trip to save the same amount, $5, at a calculator price of $125 – an example of the so-called cropping effect.

In another Kahneman-Tversky experiment, students were told about a fictitious 31-year-old Linda who was an activist in college and “was deeply concerned about issues of discrimination and social justice and had participated in anti-nuclear demonstrations.”

Students were then asked which was more likely: Linda is a bank teller or Linda is a bank teller and is active in the feminist movement. The vast majority chose bank teller and active feminist, which must be a less likely choice because the probability of two conditions will always be lower than the probability of one of them. This experiment demonstrated the so-called conjunction fallacy, another way in which people sometimes fail to think logically.

One type of psychological distortion that preoccupied Dr. Kahneman in his later years was the difference between “experienced” and “remembered” well-being, and between experienced and remembered happiness or unhappiness. A remembered experience, he said, depends largely on its most extreme moment, the peak, and its end – hence the “end of peak rule.”

As a rule of thumb, if we have a pleasant experience at the end of a vacation, for example, we tend to remember the entire vacation fondly. Similarly, if we feel less pain at the end of a medical procedure, we remember the entire experience as less painful. He discovered that sometimes the remembered experience is more important than the experience itself.

Daniel Kahneman was born on March 5, 1934 in Tel Aviv, while his mother was visiting relatives in the then British Mandate of Palestine. The Kahnemans settled in France, and young Daniel was raised in Paris, where his mother was a housewife and his father was the head of research at a cosmetics company.

During World War II, he was forced to wear a Star of David after the city was captured by Nazi German troops in 1940. One night in 1941 or 1942, he later recalled, he was outside the German-imposed Jewish curfew, visiting a friend, and turned his sweater inside out. side to hide the star as he walked the few blocks home. Then he met an SS soldier who called him, picked him up and hugged him.

“I was terrified that he would notice the star under my sweater,” Dr. Kahneman noted in a biographical essay prepared for the Nobel Prize ceremony. But the German took out his wallet, showed the boy’s photo, gave him some money and sent him away. “I returned home more certain than ever that my mother was right: people were infinitely complex and interesting.”

As the Nazis stepped up mass arrests of French Jews, Dr. Kahneman’s father narrowly escaped deportation to a death camp. The family fled to still uninhabited Vichy France, where they eventually found refuge in a henhouse in the seaside town of Cagnes-sur-Mer. In November 1942, the Germans took control of Vichy France.

As Lewis noted in his book, Dr. Kahneman had to hide in plain sight, attending school but avoiding social contact with teachers and classmates. Lewis wrote that he found human personality extremely interesting, but “his survival depended on his keeping to himself.”

The Germans and their French collaborators intensified their search for hiding Jews. Dr. Kahneman’s father, a diabetic, had increasing difficulty securing medication and died of complications from the disease just six weeks before the Allied D-Day invasion. “I was really angry about his death,” Dr. Kahneman told Lewis. “Was good. But he wasn’t strong.

After the war, Dr. Kahneman moved with his mother and sister to what soon became the state of Israel. At the age of 15, he passed a professional exam, which confirmed that he had the makings of a psychologist. He graduated from Hebrew University in 1954 with a bachelor’s degree in psychology and mathematics. He fulfilled part of his obligation to serve in the military by developing character assessment tests for recruits.

In 1961, Dr. Kahneman earned his doctorate in psychology from the University of California, Berkeley, and returned to the Hebrew University as a lecturer. There he met Tversky, who was gaining a reputation as one of the greatest psychologists of his generation.

Dr. Kahneman’s first marriage to Irah Kahn ended in divorce. In 1978, he married Anne Treisman, a cognitive psychologist who studied the mechanisms of perception and attention. Before joining Princeton in 1993, they taught at the University of British Columbia and Berkeley.

Meanwhile, Tversky took a position at Stanford University. The physical separation made working with Dr. Kahneman difficult, if not impossible, and the friendship soured.

By the late 1980s, Dr. Kahneman came to the conclusion that Tversky had not sufficiently appreciated his contributions to their work, and Tversky had his own complaints about Dr. Kahneman. “I kind of divorced him,” Dr. Kahneman said later. The two renewed their friendship in the months before Tversky’s death from melanoma in 1996.

Treisman died in 2018. Dr. Kahneman later lived with Barbara Tversky, the widow of his longtime collaborator.

In addition to Tversky, his partner of four years, the victims include two children from his first marriage, Michael Kahneman and Lenore Shoham; four stepchildren: Jessica, Daniel, Stephen and Deborah Treisman; and seven grandchildren.

Dr. Kahneman received the Presidential Medal of Freedom from President Barack Obama in 2013, the nation’s highest civilian honor. A staunch pessimist, he said he and his wife did not expect to win the Nobel Prize, despite a number of honors received over the years.

“We thought the probability was 0.2,” Treisman told the Philadelphia Inquirer after Dr. Kahneman’s award was announced. “We were very curious who would win.”