The availability heuristic is a rule of thumb, heuristic, or cognitive bias, where people base their prediction of an outcome on the vividness and emotional impact rather than on actual probablity. A rule of thumb is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination. ... Heuristic is the art and science of discovery and invention. ... Cognitive bias is any of a wide range of observer effects identified in cognitive science and social psychology including very basic statistical, social attribution, and memory errors that are common to all human beings. ...

An everyday example would be the statement: "Sorry I'm late—I hit every red light on the way here." Here the aggravation of the red lights made them seem more prevalent than they actually were.

This phenomenon was first reported by psychologists Amos Tversky and Daniel Kahneman, who also identified the representativeness heuristic. To see how availability differs from related terms vivid and salience, see availability, salience and vividness. A psychologist is a scientist who studies psychology, the systematic investigation of the human behavior and mental processes. ... Amos Tversky (March 16, 1937 - June 2, 1996) was a pioneer of cognitive science, a longtime collaborator of Daniel Kahneman, and a key figure in the discovery of systematic human cognitive bias and handling of risk. ... Daniel Kahneman Daniel Kahneman (born March 5, 1934 in Tel Aviv, in the then British Mandate of Palestine, now in Israel), is a key pioneer and theorist of behavioral finance, which integrates economics and cognitive science to explain seemingly irrational risk management behavior in human beings. ... The representativeness heuristic is a heuristic wherein we assume commonality between objects of similar appearance. ... Because too much data can cause “cognitive clutter”, individuals need a system to enable them to rank available data in terms of its immediate importance. ... Availability, salience and vividness are three terms which refer to very similar things in psychology but have slightly different meanings. ...

Overview

One important corollary finding to this heuristic is that people asked to imagine an outcome tend to immediately view it as more likely than people that were not asked to imagine the specific outcome. If group A was asked to imagine a specific outcome and then asked if it was a likely outcome, and group B was asked whether the same specific outcome was likely without being asked to imagine it first, the members of group A tend to view the outcome as more likely than the members of group B, thereby demonstrating the tendency toward using an availability heuristic as a basis for logic^{[citation needed]}. A theorem is a statement which can be proven true within some logical framework. ...

In one experiment that occurred before the 1976 US Presidential election, participants were asked simply to imagine Gerald Ford winning the upcoming election. Those who were asked to do this subsequently viewed Ford as being significantly more likely to win the upcoming election, and vice versa for participants that had been asked to imagine Jimmy Carter [Carroll, 1978]. Analogous results were found with vivid versus pallid descriptions of outcomes in other experiments. Presidential electoral votes by state. ... Gerald Rudolph Ford, Jr. ... James Earl Jimmy Carter, Jr. ...

Availability effects in lethal events

When asked to rate the probability of a variety of causes of death people tend to rate more "newsworthy" events as more likely. People often rate the chance of death by plane crash higher after plane crashes, and death by natural disaster as too likely only because these events are more reported than more common causes of death. Other rare forms of death are also seen as more common than they really are because of their inherent drama: shark attacks, terrorism, etc.

Denial as a reverse availability heuristic

An opposite effect of this bias, called denial, occurs when an outcome is so upsetting that the very act of thinking about it leads to an increased refusal to believe it might occur. In this case, being asked to imagine the outcome actually made participants view it as less likely.

References

• Tversky, A., & Kahneman, D. (1973). Availability: a heuristic for judging frequency and probability. Cognitive Psychology, 5, 207-232.
• Tversky, A. & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185, 1124-1130.
• Combs, B. & Slovic, P. (1979). Newspaper coverage of causes of death. Journalism Quarterly, 56, 837-843.
• Carroll, J. S. (1978). The effect of imagining an event on expectations for the event: An interpretation in terms of the availability heuristic. Journal of Experimental Social Psychology, 14, 88-96.

See also

• gambler's fallacy
• misleading vividness
• Texas sharpshooter fallacy
• List of cognitive biases

The gamblers fallacy is a logical fallacy which encompasses any of the following misconceptions: A random event is more likely to occur because it has not happened for a period of time; A random event is less likely to occur because it has not happened for a period of... The logical fallacy of misleading vividness involves describing some occurrence in vivid detail, even if it is an exceptional occurrence, to convince someone that it is a problem. ... The Texas sharpshooter fallacy is a logical fallacy where a cluster of statistically non-significant data is taken from its context, and therefore thought to have a common cause. ... Cognitive bias is distortion in the way we perceive reality (see also cognitive distortion). ...

External links

• Changingminds.org: Availability heuristic