Accession Number : ADA131801

Title :   External versus Intuitive Reasoning: The Conjunction Fallacy in Probability Judgment.

Descriptive Note : Tecnical rept.,

Corporate Author : STANFORD UNIV CA DEPT OF PSYCHOLOGY

Personal Author(s) : Tversky,Amos ; Kahneman,Daniel

PDF Url : ADA131801

Report Date : Jun 1983

Pagination or Media Count : 71

Abstract : Perhaps the simplest and the most basic qualitative law of probability is the conjunction rule: the probability of a conjunction P (A&B) cannot exceed the probabilities of its constituents, P(A) and P(B), because the extension (or the possibility set) of the conjunction is included in the extension of its constituents. Judgments under uncertainty, however, are often mediated by intuitive heuristics that are not bound by the conjunction rule. A conjunction can be more representative than one of its constituents and instances of a specific category can be easier to imagine or retrieve than instances of a more inclusive category. The representativeness and availability heuristics therefore can make a conjunction appear more probable than one of its constituents. This phenomenon is demonstrated in a variety of contexts including estimation of word frequency, personality judgment, medical prognosis, decision under risk, suspicion of criminal acts and political forecasting. Systematic violations of the conjunction rule are observed in judgments of lay people and of experts in both between-subjects and within-subjects comparisons.

Descriptors :   *JUDGEMENT(PSYCHOLOGY), *COGNITION, *REASONING, *PERFORMANCE(HUMAN), *HEURISTIC METHODS, PROBABILITY, DECISION MAKING, PROBLEM SOLVING, BEHAVIOR, PREDICTIONS, SCENARIOS, PERCEPTION(PSYCHOLOGY), REACTION(PSYCHOLOGY), SOCIAL PSYCHOLOGY

Subject Categories : Psychology

Distribution Statement : APPROVED FOR PUBLIC RELEASE