Amos Tversky invited to a Jerusalem psychology seminar

Amos Tversky invited to a Jerusalem psychology seminar was the initiating encounter for Daniel Kahneman’s most consequential intellectual collaboration. In 1969, while teaching in the Department of Psychology at the Hebrew University of Jerusalem, Kahneman asked Tversky to speak as a guest. The seminar turned an acquaintance with a brilliant young researcher into a sustained inquiry whose consequences reached from intuitive statistics to prospect theory, framing effects, and public policy.

The Invitation and Its Setting

The invitation took place on what Kahneman remembers as a lucky day in 1969. Tversky was thirty-two and Kahneman thirty-five. Tversky was already regarded as a rising star in decision research and, by many who knew him, as the most intelligent person they had ever encountered. Kahneman presents him as brilliant, voluble, and charismatic, with a perfect memory for jokes and an exceptional ability to use them to make a point. His presence made the seminar intellectually vivid rather than merely instructional.

The setting was the Department of Psychology at the Hebrew University of Jerusalem, a location that mattered because the encounter grew directly out of teaching and discussion rather than from a formal research plan. The seminar gave Tversky a platform, Kahneman an unexpected interlocutor, and both men a problem sufficiently concrete to pursue together.

The Seminar’s Question

Tversky spoke about an ongoing research program at the University of Michigan that asked whether people were good intuitive statisticians. The comparison was with intuitive grammar: a four-year-old can effortlessly follow grammatical rules without knowing that those rules exist. The question was whether people possessed a comparable intuitive grasp of basic statistical principles.

The initial answer was a qualified yes, but the discussion moved Kahneman and Tversky toward a qualified no. Their conclusion was not that people lacked all statistical ability. Rather, ordinary intuition could appear competent while systematically misjudging the reliability of evidence, especially when statistical reasoning required sensitivity to sample size and replication.

The seminar therefore became an instance of the phenomenon it examined. The two researchers were not detached observers of faulty intuition. Despite years of teaching and using statistics, they recognized that their own intuitions about the reliability of results from small samples were deficient. They were too willing to believe findings based on inadequate evidence and inclined to collect too few observations in their own research.

From Conversation to Research

Kahneman and Tversky enjoyed the exchange and decided that intuitive statistics would be an interesting subject for joint investigation. That decision became concrete the following Friday, when they met for lunch at Café Rimon, a favorite gathering place for bohemians and professors in Jerusalem. There they planned a study of the statistical intuitions of sophisticated researchers.

Their survey used realistic research scenarios. Tversky collected responses at a meeting of the Society of Mathematical Psychology, including answers from expert participants and the authors of two statistical textbooks. The results confirmed the concern that had emerged in the seminar: the experts greatly exaggerated the likelihood that an experimental result from a small sample would successfully replicate, and they gave poor advice to a fictitious graduate student about how many observations to collect. Even statisticians were not good intuitive statisticians.

The finding transformed an engaging seminar debate into a research program. The collaboration’s method was already visible in miniature: invent a problem, examine the immediate judgment it elicited, test that judgment against evidence, and identify the systematic error when intuition failed. The seminar supplied not merely a topic but a shared habit of inquiry.

The Collaboration’s Consequences

The partnership later expanded from statistical judgment to decisions under risk. For years, Kahneman and Tversky spent many hours in conversation—in offices, restaurants, and on long walks through Jerusalem—creating simple decision problems and asking which option seemed immediately tempting. Their interest was not initially in the most rational or advantageous choice, but in the intuitive choice that appeared compelling.

Five years after beginning their study of gambles, they completed “Prospect Theory: An Analysis of Decision under Risk.” The theory was descriptive rather than prescriptive: it documented and explained systematic violations of the axioms of rationality in choices between gambles. It departed from utility theory by showing that outcomes are evaluated relative to a reference point, so a result can be experienced as a gain or a loss depending on the earlier state against which it is judged. The added variable made prospect theory more complex than Bernoulli’s model, but it also enabled the theory to explain patterns that the simpler model could not.

The article’s publication in Econometrica proved consequential. The venue placed the work inside economics and decision theory, where it could influence the discipline that assumed the rational agent, rather than leaving it confined to a psychological journal. Two years later, Kahneman and Tversky published an account of framing effects in Science, showing that inconsequential changes in wording could produce large changes in preferences.

Intellectual and Institutional Legacy

The seminar’s original question eventually became part of a larger challenge to the image of the fully rational Econ. Humans, as Kahneman describes them, are affected by System 1, limited by the information available at a given moment, and unable consistently to avoid priming, WYSIATI, narrow framing, the inside view, or preference reversals. The research did not establish that people were irrational in the ordinary sense of being impulsive or impervious to argument. It showed instead that Humans are not well described by the rational-agent model.

That conclusion had policy consequences. Because Humans often need help to make accurate judgments and better decisions, Richard Thaler and Cass Sunstein developed libertarian paternalism in Nudge: institutions could arrange choice architecture to serve people’s long-term interests while preserving their ability to opt out. Default enrollment in pension plans, automatic health-insurance enrollment, clearer disclosures, the replacement of the Food Pyramid with the Food Plate, and balanced presentation of meat-label information all exemplify applications of the psychological tradition that began with the seminar’s concern about intuitive error.

The invitation thus has a significance disproportionate to its modest form. A guest lecture led to a disagreement; the disagreement led to lunch at Café Rimon; lunch led to a survey that exposed experts’ statistical weaknesses; and the shared investigation eventually produced prospect theory, framing research, and a practical vocabulary for understanding judgment and choice. What began as an invitation became the origin point of a collaboration that changed both psychology and economics.