Representativity heuristic

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The representativity heuristic is a judgment heuristic (judgment decision rule) in which the probability of events is assessed according to how closely they correspond to certain prototypes. This also happens with objects that are to be assessed in classes. Objects that appear representative of a certain class are assigned to a class with too high a probability. This doesn't always lead to complete misjudgments - intuitive impressions are often more accurate than actual estimates based on probabilities.

Experiments by Kahneman and Tversky

In a classic study, Daniel Kahneman and Amos Tversky (1973) offered their test subjects a written description of a woman named Linda. It reported a great deal about Linda's work for women's rights and emancipation. Then the test persons were asked what, after this description, was more likely that Linda was “a bank clerk” or “a bank clerk and a feminist”. The majority of the test persons estimated the probability that Linda was “a bank clerk and a feminist”, much higher (conjunction effect).

This assessment is wrong, however, because the probability that both events will occur simultaneously cannot be greater than the probability that one of the two events will occur alone. Even if all bank employees are also feminists, the two probabilities for (1) “bank employee” and for (2) “bank employee and feminist” would be the same.

Another important study by Kahneman and Tversky (1973) demonstrates the occurrence of the so-called base rate error ( prevalence error or base rate neglect ). The test subjects in two groups were given brief descriptions that were compatible with the stereotype of the “ lawyer ” or “ engineer ” (e.g. “Jack is 45 years old. He is married with four children. He is generally conservative, careful and ambitious. He has no interest in politics or social issues and spends most of his free time on one of his many hobbies such as carpentry, sailing and math brain teasers. " The base rate was varied by informing the test participants that this personal description resulted from interviews that 30 lawyers and 70 engineers had undergone. The test subjects' task was to estimate the likelihood of an engineer (or lawyer). The different initial probabilities had little influence on the judgment, as the test subjects made the assignment based on the external description. As a result, there were frequent errors of judgment.

The base rate neglect, i.e. H. Kahneman and Tversky explain the overestimation of the conditional probability of events with a low base rate by using the representativity heuristic. More recent explanations for this error in the judgment process can be found in Gigerenzer and Hoffrage (1995) (presentation format) and Fiedler et al. (2000) ( sampling effect ).

Implications

Another implication arises from the fact that people neglect the sample size. A small excerpt from a process is seen as representative of the entire process and after a short time a pattern for all events is recognized. These patterns do not have to be right and can therefore be misleading. An example of this: You have two samples with the height of men. The first sample contains ten measurements, the second 1000. You know that the men in the population from which the samples were measured average 1.70 meters tall. When assessing how likely it is that the respective mean of the samples is exactly 1.70 meters, most people give both samples the same probability. However, this is wrong. The probability that the sample with the higher number of measurements is exactly 1.70 meters is higher.

It also comes to the player's fallacy .

See also

literature

  • K. Fiedler, B. Brinkmann, T. Betsch, B. Wild: A sampling approach to biases in conditional probability judgments: Beyond base rate neglect and statistical format. In: Journal of Experimental Psychology: General. Vol. 129, No. 3, 2000, pp. 399-418.
  • G. Gigerenzer, U. Hoffrage: How to improve Bayesian reasoning without instruction: Frequency formats. In: Psychological Review. Volume 102, 1995, pp. 684-704.
  • G. Pennycook, VA Thompson: Base-rate neglect. In: RF Pohl (Ed.): Cognitive illusions: Intriguing phenomena in thinking, judgment, and memory. 2nd Edition. Routledge, London / New York 2017, pp. 44–61.
  • KH Teigen: Judgments by representativeness. In: RF Pohl (Ed.): Cognitive illusions: Intriguing phenomena in thinking, judgment, and memory. 2nd Edition. Routledge, London / New York 2017, pp. 204–222.
  • A. Tversky, D. Kahneman: Availability: A heuristic for judging frequency and probability. In: Cognitive Psychology. Volume 42, 1973, pp. 207-232.

Individual evidence

  1. ↑ David G. Myers : Psychology. Springer, Berlin 2008, ISBN 978-3-540-79032-7 , p. 437.
  2. ^ A b c Hanno Beck : Behavioral Economics: an introduction. Springer Gabler, Wiesbaden 2014, ISBN 978-3-658-03366-8 , pp. 28-38.
  3. ↑ Daniel Kahneman: Fast thinking, slow thinking. From the English by Thorsten Schmidt. 3. Edition. Siedler Verlag, Munich 2011, ISBN 978-3-328-10034-8 , p. 190.