Jerusalem is the formative setting for the collaboration between Daniel Kahneman and Amos Tversky, the partnership that supplied the book’s intellectual origin and ultimately changed how systematic error in judgment and choice is understood. In the city, a psychology seminar became the first testing ground for their questions, Café Rimon became the place where a research program was planned, and long conversations and walks developed into a method that produced some of the most influential work in modern behavioral science.

Seminar and First Encounter

Jerusalem first appears through the Department of Psychology at the Hebrew University of Jerusalem, where Daniel Kahneman was teaching a seminar in 1969. He invited Amos Tversky, then a thirty-two-year-old rising star in decision research, to speak to the class. Tversky was remembered as brilliant, voluble, charismatic, exceptionally funny, and gifted with a perfect memory for jokes that he could turn into arguments. Kahneman, five years older, expected an intellectually lively meeting; the encounter became the beginning of a fourteen-year collaboration.

Tversky spoke about an ongoing research program at the University of Michigan that asked whether people were good intuitive statisticians. The seminar contrasted intuitive grammar, which children use competently without knowing its rules, with the possibility of an equally natural intuitive grasp of statistical principles. The discussion initially produced a qualified yes, but Kahneman and Tversky ultimately judged that a qualified no was more accurate. Jerusalem therefore functions not merely as a backdrop but as the site where an apparently ordinary question about statistical intuition was converted into a shared research problem.

Café Rimon and the Research Program

That Friday, Kahneman and Tversky met for lunch at Café Rimon, described as a favorite gathering place for bohemians and professors in Jerusalem. There they planned a study of the statistical intuitions of sophisticated researchers. The setting linked intellectual exchange with the informal social life of the city: the project did not begin as a remote institutional program but as a conversation carried into a familiar meeting place.

Their plan was sharpened by an admission that included themselves. Despite years of teaching and using statistics, both researchers lacked an intuitive sense of how unreliable results from small samples could be. They were too willing to believe findings based on inadequate evidence and were inclined to collect too few observations in their own research. The proposed survey would therefore examine whether other researchers suffered from the same weakness rather than treating professional expertise as protection against intuitive error.

The resulting questionnaire presented realistic research scenarios involving statistical judgment. Tversky collected responses from expert participants at a meeting of the Society of Mathematical Psychology, including two authors of statistical textbooks. The experts, like Kahneman and Tversky, greatly exaggerated the probability that an experimental result based on a small sample would replicate and gave poor advice about the number of observations a fictitious graduate student should collect. The Jerusalem conversation thus led to a finding with an uncomfortable scope: even statisticians were not good intuitive statisticians.

Collaboration in the City

The work begun in Jerusalem quickly acquired a distinctive rhythm. While writing the article reporting their findings, Kahneman and Tversky discovered that they enjoyed working together. Their amusement made long periods of concentrated work easier and helped them remain patient in pursuit of precision. Although both were critical and argumentative, neither rejected the other’s ideas out of hand. Tversky often clarified the point of Kahneman’s vague intuitions, while Kahneman contributed a stronger grounding in the psychology of perception. Tversky was more logical and theory-oriented; Kahneman was more intuitive. Their differences created surprise without preventing mutual understanding.

They developed a routine of spending much of their working days together, often walking for long periods. Their research became a continuing conversation in which they invented questions, examined their first intuitive answers, and treated each question as a small experiment. They were not initially seeking the formally correct response to a statistical problem. Instead, they wanted to identify the answer that came to mind first, including the answer they felt tempted to give even when they knew it was wrong. The shared setting of Jerusalem helped sustain this conversational method, in which informal exchange became a disciplined instrument for exposing the machinery of judgment.

One playful exercise involved several toddlers known to both researchers. They independently imagined that the argumentative three-year-old would become a lawyer, the nerdy child a professor, and the empathetic but mildly intrusive child a psychotherapist. The predictions were absurd, yet their appeal revealed that judgments were being driven by resemblance to cultural stereotypes. This insight became part of a theory of representativeness and prediction that they later tested in dozens of experiments.

From Jerusalem to a Wider Science

The collaboration that took shape in Jerusalem extended far beyond the city. Over several years, Kahneman and Tversky studied biases in assigning probabilities, forecasting the future, assessing hypotheses, and estimating frequencies. 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 in intuitive thought and treated roughly twenty biases as manifestations and demonstrations of those heuristics.

The work challenged two widely accepted assumptions in 1970s social science: that people were generally rational and that departures from rationality were mainly caused by emotions such as fear, affection, or hatred. Kahneman and Tversky instead documented systematic errors in normal thinking and traced them to the design of cognition itself. Their article attracted more attention than 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 ideas were subsequently used in medical diagnosis, legal judgment, intelligence analysis, philosophy, finance, statistics, and military strategy.

The same partnership later turned from judgment to decision making under uncertainty. Their work on simple gambles led to “Prospect Theory: An Analysis of Decision under Risk,” published five years after the Science article and regarded as one of the foundations of behavioral economics. The collaboration continued until geographical separation made it too difficult to sustain. Kahneman later received the 2002 Nobel Prize for work whose central basis was the collaboration; Tversky would have shared the prize had he not died in 1996 at the age of fifty-nine.

Narrative Significance

Jerusalem gives the book’s intellectual history a precise origin: a seminar, a disagreement about intuitive statistics, a Friday lunch at Café Rimon, and a partnership formed through repeated conversation. The city is associated with the moment when private intuitions became public experiments. Its significance lies in the contrast between the modest scale of the beginning and the breadth of the consequences. A question raised in a university classroom and developed over lunch became a research program about how ordinary minds use heuristics, generate predictable biases, and depart from the logic of probability and rational choice.

The city also remains embedded in the book’s larger method. Kahneman and Tversky learned to treat their own immediate answers as evidence—not as authority, but as phenomena to be examined. Jerusalem is therefore the place where the book’s central discipline was established: notice the first thought, question its apparent coherence, and test whether an individual intuition is part of a wider and repeatable pattern.