Amos Tversky (1937-1996) was one of the most important cognitive psychologists of the 20th century, known primarily for his collaboration with Daniel Kahneman that produced the heuristics and biases research program and prospect theory. A mathematical psychologist of extraordinary rigor and creativity, Tversky brought formal precision to the study of how people make judgments and decisions under uncertainty. Had he lived, he would certainly have shared Kahneman's Nobel Prize.
Key Contributions
With Kahneman, Tversky demonstrated that human judgment systematically departs from rational norms in predictable ways. Their 1974 Science paper "Judgment Under Uncertainty: Heuristics and Biases" introduced the availability, representativeness, and anchoring heuristics. Prospect theory (1979), their model of decision-making under risk, showed that people evaluate outcomes relative to a reference point, are loss-averse (losses loom larger than equivalent gains), and weight probabilities nonlinearly (overweighting small probabilities and underweighting large ones). Prospect theory became the most cited paper in economics.
Beyond his collaboration with Kahneman, Tversky made fundamental contributions to measurement theory, similarity judgment (his contrast model showed that similarity is not symmetric and depends on the features of both items), and the foundations of decision theory. His elimination by aspects model proposed that choices are made by sequentially eliminating options that fail to meet criteria on important attributes — a satisficing strategy consistent with bounded rationality. His features of similarity work showed that people judge similarity by comparing shared and distinctive features, weighted by their salience and diagnosticity.