Daniel Kahneman, who revolutionized the perception of rationality, dies

Daniel Kahneman, an Israeli psychologist with a laureate in another field, economics, passed away this Wednesday (27) at the age of 90. Based in the United States, he had lived for many years on the island of Manhattan, in New York, and taught mainly at Princeton University since 1993. His wife, Barbara, preferred not to disclose the place or cause of death.

In four hands, with his collaborator Amos Tversky (1937-1996), Kahneman’s main intellectual achievement was to overthrow, in the 1970s, the idea of Homo economicus — the human being interpreted in the premises of economics as a perfectly rational being when making decisions, including economic ones. The two are considered pioneers in the field of behavioral economics, and their work was recognized in 2002 with an economic sciences award in memory of Alfred Nobel, from the Central Bank of Sweden.

Kahneman’s legacy to psychology and economics

At the bestseller “Fast and slow: two ways of thinking” (Objetiva, 2012), Kahneman explains that until the 1970s social scientists “mostly accepted two ideas about human nature”. The first is that “people are generally rational and their thinking is normally sane”. The second is that “emotions such as fear, affection and hatred explain most of the occasions in which people break with rationality”.

The two Israelis cast doubt on both ideas, investigating systematic errors, or biases, that are part of the structure of the human mind. Then it would not be the case that emotions are to blame for clouding reason, but that there are “errors in the design of the machinery of cognition”. Furthermore, the psyche would operate in two modes: a System 1, faster, automatic, instinctive, for first impressions and more subject to bias; and a System 2, slower and more expensive, which coincides with what is popularly called “burning your eyelashes” and leaves the usual and automatic.

The popular idea that it is possible to influence the sex of an unborn baby, for example, would be derived from a cognitive bias that leads us to interpret random patterns as if they had a causal link with external factors. When seeing a sequence of births of, for example, six boys in a row from the same mother, we tend to think (with System 1) that this must have a cause other than chance compared to a sequence in which the sexes appear to alternate at intervals. varied.

Why do these errors happen? One reason is that “assuming causality could have evolutionary advantages,” that is, advantages for survival and reproduction. “We are automatically aware of the possibility that the environment has changed. Lions appear on the plains at random times, but it would be safer to notice and respond to an apparent increase in the rate of appearance of lion prides,” even if the actual pattern is chance rather than increase, the psychologist explained — with this type of of explanation, in addition to integrating psychology with economics, he also contributed to an interdisciplinary conversation with biology, something rare for social scientists.

“The last few days have taught me that practically all the people I follow have something in common: admiration for Daniel Kahneman”, summarized computer scientist and essayist Paul Graham, in X. A follower of the essayist reported that reading “Quick and Devagar” saved his wife’s life: “we had to choose between two types of surgeries and we were leaning towards choosing one type based on risk aversion. Then I opened the book to the page dedicated to decision making, it was crucial to look for a better alternative”.

In his book “Psych” (Ecco Press, 2023; unpublished in Brazil), Paul Bloom, professor emeritus of psychology at Yale University, says that the area of ​​the study of cognitive biases “has its own Freud — in fact, two of them: friends and collaborators Amos Tversky and Daniel Kahneman.” Their influence led later work to propose lists of up to more than 100 biases, but Bloom does not believe the list is that extensive. In part, because since the last decade psychology has suffered a crisis of failure to reproduce study results, when they were redone. The expert reduces the list of biases to five, but Kahneman’s work survives the crisis and is still relevant.

Canadian philosopher Joseph Heath, in the book “Enlightenment 2.0”, makes an effort to recover the ideal of human rationality after Kahneman’s revelations. “The insidious nature of cognitive bias is that It’s your own brain that is doing this to you,” Heath acknowledges, “so that it is not possible to discern by introspection when the misleading is happening.” Just knowing that we have biases, and what they are, is not enough for us to be wiser or more rational, he points out. Heath’s solution is familiar to cognitive-behavioral therapists: change the environment. Just as pencil and paper make us more rational and less prone to error in mathematics, we can create environments more conducive to rationality, which depends on slow processes in the individual brain and cultural tricks accumulated in communities committed to rigorous thinking.

Daniel Kahneman’s youth

When Kahneman was born in Tel Aviv in 1934, there was not a State of Israel, but a British Mandate of Palestine. His parents, Lithuanian Jews, were just visiting, the family home was in Paris. His father researched chemistry for an industry. The psychologist said that the family’s roots in France were shallow, as they did not feel safe — which was only confirmed with Hitler’s invasion in the 1940s.

It was when the Second World War was still raging, in 1941, that the seven-year-old boy drew his first graphic. These were figures from the family’s fortune, in precipitous decline in the wake of the Holocaust. “I will never know whether my vocation as a psychologist resulted from my early exposure to interesting gossip,” Kahneman joked in an autobiographical article for the Nobel Prize page, “or whether my interest in gossip was an indication of a budding vocation. Like many other Jews, I suppose, I grew up in a world that consisted exclusively of people and words, and most words were about people.”

In her mother’s gossip, some people were better than others, “but the best were far from perfect and no one was just plain bad.” The stories were full of irony and all had two sides or more.

In invaded France, as a boy, he was forced to wear a Star of David on his lapel and respect the 6pm curfew. Once, he accidentally ran into a Nazi SS soldier after the deadline, because he was too distracted playing with a little Christian friend. The soldier wore a black uniform that he had learned to fear. As he approached, with a tight step, he was approached by the Nazi. The man picked him up, gave him a hug, and spoke emotionally in German. He opened his wallet, showed his son’s photo, and gave him money. “I went home more certain than ever that my mother was right: people were infinitely complicated and interesting,” he reflected.

At the age of 17, Israel already existed and asked him to serve in the armed forces. The boy, more inclined towards intellect than physicality, managed to combine service with his passion for writing. It was then that he decided he would become a psychologist. The career guidance test confirmed: psychology was the first recommendation — economics was the second. In two years, Kahneman completed his degree in psychology at the Hebrew University of Jerusalem, with an important specialization in mathematics that would mark the quantitative rigor of his research later, but “he was mediocre in mathematics”, he confessed.

At the age of 20, he was already applying his knowledge as a second lieutenant in the Israel Defense Forces. But it was at the end of the following decade, in the 1960s, when he was teaching at the university where he graduated, that Kahneman met his youngest collaborator, Amos Tversky. Of the eight joint articles they published during the 1970s, five were cited by other researchers more than a thousand times. Tversky died of cancer in 1996. His wife was the same Barbara, now twice widowed. Kahneman also left behind two children from his first marriage, four stepchildren and seven grandchildren.