What is the availability heuristic?

The availability heuristic is a mental shortcut for estimating how common or probable something is, based on how readily examples come to mind. If many instances are easy to recall, the event is judged to be frequent or likely. The APA Dictionary of Psychology credits the description of the idea to Amos Tversky and Daniel Kahneman in 1973, and it is also called the availability bias when it leads to mistakes. [1] [2]

Tversky and Kahneman's 1973 paper in Cognitive Psychology describes people evaluating the frequency of classes or the probability of events by the ease with which relevant instances come to mind. They noted that availability is generally correlated with real-world frequency, but is also affected by other factors, so relying on it produces systematic biases. They demonstrated such biases in judgments of word classes, combinatorial outcomes and repeated events, and they explained illusory correlation as an availability bias. [2]

Frequent events tend to be easier to recall than rare ones, so the shortcut often gives fast and fairly accurate judgments. Simply Psychology, citing Markman and Medin, notes it errs when rarer events happen to be easier to recall. This tends to occur when something is dramatic, recent, emotionally engaging, heavily reported or personally experienced. The error is therefore directional rather than random. [3]

The APA gives plane crashes as an example: well-publicized events can seem more probable than they are, while less publicized causes of death, such as diabetes, can seem less probable than they are. Verywell Mind offers a similar illustration: police shootings may make policing seem the more dangerous job, yet statistics show loggers are likelier to die at work. It also says that after seeing several news reports about car thefts, a person may judge vehicle theft to be more common locally than it is. [1] [4]

Simply Psychology describes availability as a feeling rather than a count: people need not retrieve any examples to sense it. It cites Schwarz and colleagues (1991), who found that participants who found a recall task easy rated themselves as more assertive than those who found it hard, even though the easy-task group recalled fewer examples. The same source says Schwarz et al. were critiqued as leaving the underlying process ambiguous. [3]

A 2018 meta-analysis by Weingarten and Hutchinson, as summarized by Simply Psychology, pooled 142 papers, 263 studies and 582 effect sizes. It found a medium-sized average effect for the standard ease-of-retrieval manipulation, but publication bias inflated the naive estimate by up to a third. Felt ease explained only part of the effect; other factors, such as the content people actually recalled, accounted for the rest. The authors concluded that the effect is real and meaningful, but that classic demonstrations overstate its typical strength. [3]

The availability heuristic is sometimes confused with the representativeness heuristic, which judges probability by how well an example matches one already in mind, rather than by how easily similar events are recalled. [4]