The First collaboration meeting with Amos Tversky was the decisive origin of Daniel Kahneman and Amos Tversky’s research partnership. A guest seminar at the Hebrew University of Jerusalem in 1969 led from an argument about whether people were intuitive statisticians to a lunch at Café Rimon, where the two psychologists decided to investigate the question together. That encounter established not only their subject but also the conversational method, intellectual complementarity, and shared skepticism that would shape some of the most influential work in modern social science.

The Seminar and Its Question

The meeting began when Daniel Kahneman invited Amos Tversky to speak to a seminar he was teaching in the Department of Psychology at the Hebrew University of Jerusalem. Tversky was thirty-two and Kahneman thirty-five. Kahneman already regarded Tversky as a rising star: he was brilliant, voluble, charismatic, gifted with a perfect memory for jokes, and unusually able to use humor to make an intellectual point. The seminar therefore promised not merely information but an encounter with a forceful and entertaining thinker.

Tversky presented an ongoing University of Michigan research program that asked whether people were good intuitive statisticians. The comparison was with intuitive grammar: a four-year-old can speak according to grammatical rules without knowing that those rules exist. The question was whether people possessed a similarly effortless grasp of basic statistical principles. The discussion initially allowed for a qualified yes, but the debate ultimately moved Kahneman and Tversky toward a qualified no. People might reason successfully in some statistical situations, yet their immediate judgments could systematically depart from statistical logic.

The Lunch at Café Rimon

Kahneman and Tversky enjoyed the exchange enough to decide that intuitive statistics deserved joint investigation. That Friday they met for lunch at Café Rimon, a favorite gathering place for bohemians and professors in Jerusalem, and planned a study of the statistical intuitions of sophisticated researchers. The choice of participants was important: they were not setting out to expose only ordinary people’s mistakes. They wanted to know whether professional experience with statistics protected researchers from the same errors.

Their first target was their own intuition. Despite years of teaching and using statistics, both recognized that they lacked an intuitive sense of the reliability of results obtained from small samples. They were too willing to believe research findings based on inadequate evidence and too prone to collect too few observations in their own studies. The proposed research consequently had a reflexive quality: before diagnosing other researchers, the two investigators acknowledged that the problem belonged to them as well.

From Joint Test to Shared Discovery

The pair prepared a survey containing realistic scenarios involving statistical issues that arise in research. Tversky collected responses from expert participants at a meeting of the Society of Mathematical Psychology, including the authors of two statistical textbooks. The results confirmed their concern. The experts greatly exaggerated the probability that an experimental result would successfully replicate even when the original study used a small sample, and they gave poor advice to a fictitious graduate student about how many observations she needed. Expertise in statistics had not produced reliable intuitive statistics.

The encounter also revealed why collaboration between them could work so productively. While writing the article reporting the findings, Kahneman and Tversky discovered that they enjoyed working together. Tversky’s humor made Kahneman funny as well, and their hours of work passed in continuous amusement. That pleasure made them unusually patient: striving for perfection became easier when the work was never boring. Although both were critical and argumentative, neither rejected the other’s ideas out of hand. Tversky often saw the point of Kahneman’s vague ideas more clearly than Kahneman himself did.

Their differences became an intellectual resource rather than an obstacle. Tversky was the more logical thinker, oriented toward theory and possessed of an unfailing sense of direction. Kahneman was more intuitive and rooted in the psychology of perception, from which they borrowed many ideas. They were similar enough to understand one another easily and different enough to surprise one another. They soon developed a routine of spending much of their working days together, often on long walks, and for the next fourteen years the collaboration became the focus of their lives and, in Kahneman’s judgment, the source of the best work either had done.

The Method Born from the Meeting

The research practice established after the meeting was itself a major consequence of the event. Their work took the form of conversation: they invented questions and jointly examined their intuitive answers. Each question functioned as a small experiment, and they could conduct many such experiments in a single day. They were not initially trying to discover the correct answer to a statistical problem. Instead, they wanted to identify the intuitive answer—the first response that came to mind, including the response they felt tempted to give even when they knew it was wrong.

They reasoned that an intuition shared by both of them would probably be shared by many other people and would therefore be relatively easy to demonstrate experimentally. A playful example involved predicting the future professions of toddlers they knew: an argumentative three-year-old seemed destined to become a lawyer, a nerdy child a professor, and an empathetic, mildly intrusive child a psychotherapist. The predictions were absurd but appealing because each child resembled a cultural stereotype. This small exercise helped them develop a theory about the role of resemblance in prediction, which they later tested and elaborated in dozens of experiments.

Long-Term Consequences

The initial collaboration expanded into several years of research on biases in intuitive thinking, including the assignment of probabilities, forecasting, hypothesis assessment, and frequency estimation. In the fifth year of their collaboration, they presented their main findings in Science in the article “Judgment Under Uncertainty: Heuristics and Biases.” The article described simplifying shortcuts used by intuitive thinking and interpreted about twenty biases as manifestations of those heuristics and as evidence of their role in judgment.

The article challenged assumptions widely held among social scientists in the 1970s. One assumption was that people were generally rational and that their thinking was normally sound. Another was that departures from rationality were mainly caused by emotions such as fear, affection, or hatred. Kahneman and Tversky instead documented systematic errors in the thinking of ordinary people and linked those errors to the design of the machinery of cognition rather than primarily to emotional corruption.

The article attracted far more attention than they had expected and became one of the most highly cited works in social science, with more than three hundred scholarly articles referring to it in 2010. Its concepts were applied in medical diagnosis, legal judgment, intelligence analysis, philosophy, finance, statistics, and military strategy. The first meeting therefore mattered not simply because two scholars began working together, but because a seminar dispute and a lunch conversation created a durable investigative program: intuitive judgments could be treated as observable, repeatable objects of study, and their errors could be described with a precise shared vocabulary.