Availability heuristic

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Availability heuristic (English availability heuristic ) is a shortening cognitive operation that leads to judgment errors. In cognitive psychology, it is one of the so-called judgment heuristics , which to a certain extent represent rules of thumb in order to be able to judge facts even when there is no access to precise and complete information. It replaces the difficult question of the frequency of an event or the scope of a category with the simpler question of how easy it is to remember suitable examples. Two common reasons why examples are easily available and thus lead to systematic error are personal experiences and reports in the mass media.

The term availability errors (English availability error ) is also common for the gambler's fallacy related cognitive bias .


The availability heuristic is used, often unconsciously, when the importance or frequency (or probability ) of an event has to be assessed, but at the same time the time, the possibility or the will is missing to access precise (e.g. statistical ) data. In such cases, judgment is instead influenced by how available that event or examples of similar events are in the mind . Events that we remember very easily therefore seem more likely to us than events that are difficult to remember. For this reason, if you have recently read a report about a murder or frequently encounter such reports in the media, the likelihood of being murdered or victim of violence could be rated as quite high.

In halls with many slot machines, gamblers tend to feed their machines with more money because they occasionally watch someone else win and then estimate their own chances to be higher. It is easier to remember the gains of others than the much more frequent losses. The fact that someone has won does not change the current odds of winning, and focusing on the number of wins is neglecting the number of losses. People make this mistake all the time, even though the odds are as bad in a group as they are on a single machine. It's just easier to remember winnings in a group than at a single machine.

Other examples:

  • "Sorry for the delay - I was red at every traffic light on the way."
  • “My friend is a choleric, a typical Aries .” (The speaker does not remember that he has met hundreds of “atypical Aries” who were not choleric, and therefore believes in the alleged connection between the character and the zodiac sign .)


In a study by Tversky and Kahneman (1973), test subjects were read out lists of proper names. In the first condition the list contained 19 names of very famous men and 20 names of less famous women, in the second condition 19 names of very famous women and 20 of less famous men. Participants were asked to assess whether there were more men or more women on the list. Over 50% of the participants remembered the very famous names better ( famous names effect) , approx. 80% overestimated the proportion of the gender with the very famous name. The application of the availability heuristic led to misjudgments, as availability was determined by the factor of celebrity and not by the group size.

Norbert Schwarz and his colleagues were able to show that it is not the number of examples that are remembered that is decisive, but the ease with which information can be processed . Test subjects were asked to remember six examples in which they behaved confidently. It was easy for most of them. Another group should find twelve such examples, which is considerably more difficult. Although the members of this group had collected more examples, they subsequently rated themselves as less confident than the first group. Even another group, whose members were asked to note twelve events in which they had behaved insecurely , felt more self-confident than the second group afterwards. They came to this judgment because it was very difficult for them to find examples of shy behavior.

The availability heuristic also plays a role when visual content that is easily imaginable for a judgment has more weight than “dry” statistics. For example, it can explain why the frequency of smoking among doctors decreases with proximity to lung cancer patients, as reported in the book by Richard Nisbett and Lee Ross.

In partnerships and working groups, conflicts arise when someone does not feel that their contributions are sufficiently valued. The availability heuristic leads to an overestimation of one's own cooperation, because everyone can easily remember it. Ross and Sicoly asked their spouses how much they participated in the housework, in initiating joint activities, but also in triggering disputes. The addition of the reported shares of both partners was always over 100%.

See also


  • Daniel Kahneman : Thinking, fast and slow. Allen Lane Paperback, 2011, ISBN 978-1-84614-606-0 , therein Chapter 12: The Science of Availability. Pp. 129-136.
  • Richard Nisbett , Lee Ross: Human inference: Strategies and shortcomings of social judgment. Prentice Hall, Englewood Cliffs, NJ 1980.
  • Amos Tversky , Daniel Kahneman: Judgment under uncertainty: Heuristics and biases. In: Max H. Bazerman (Ed.): Negotiation, decision making and conflict management. Vol 1-3. Edward Elgar Publishing, Northampton, MA, US 2005, pp. 251-258.
  • Amos Tversky, Daniel Kahneman: Judgment under uncertainty: Heuristics and biases. In: Science. 185, 1974, pp. 1124-1131.
  • Amos Tversky, Daniel Kahneman: Availability: A heuristic for judging frequency and probability. In: Cognitive Psychology. Volume 5, No. 2, 1973, pp. 207-232.
  • Rolf Reber : “Availability,” in: Rüdiger F. Pohl (Ed.): “Cognitive illusions: Intriguing phenomena in thinking, judgment and memory.” 2nd Edition. Routledge, London and New York 2017, ISBN 978-1-138-90341-8 , pp. 185-203.
  • Norbert Schwarz , Herbert Bless, Fritz Strack, Gisela Klumpp, Helga Rittenauer-Schatka, Anette Simons: Ease of retrieval as information: Another look at the availability heuristic. In: Journal of Personality and Social Psychology. Volume 61, No. 2, 1991, pp. 195-202.
  • Fritz Strack , Roland Deutsch: Judgment Heuristics. In: Dieter Frey, Martin Irle (Hrsg.): Theories of social psychology. Volume III: Theories of motivation, self and information processing. 2002, pp. 352-384.

Individual evidence

  1. www.spektrum.de: Lexicon of Psychology .
  2. ^ Norbert Schwarz et al.: Ease of retrieval as information. 1991.
  3. Michael Ross, Fiore Sicoly: Egocentric biases in availability and attribution. In: Journal of Personality and Social Psychology. Volume 37, 1979, pp. 322-336.