Availability Heuristic
Edited by Paweł Raja, PhD · Published
Definition
Availability Heuristic is a mental shortcut in which people judge how frequent or likely something is by how easily examples come to mind.
- Also known as:
- Availability bias
- Category:
- Judgment & Belief
- Impact:
- High
- Landmark study:
- Tversky & Kahneman (1973)
- Evidence here:
- 7 cited studies
Why it happens: the psychology of availability heuristic
Tversky and Kahneman (1973) described availability as one of the core heuristics of judgment. Instead of counting cases, people ask how easily examples come to mind. Usually that works, because common things are easy to recall. It misleads when recall is driven by something other than frequency — vividness, recency or media coverage.
In one of their demonstrations, people judged that more English words start with the letter K than have K as the third letter, although the opposite is true. Words are easier to retrieve by their first letter, so the first-letter category feels bigger.
Lichtenstein and colleagues (1978) found that people overestimated the frequency of dramatic, heavily reported causes of death, such as tornadoes and accidents, and underestimated quiet killers such as diabetes and stroke.
Schwarz and colleagues (1991) showed that the feeling of ease itself matters. People asked to recall 12 examples of their own assertive behavior — a hard task — later rated themselves as less assertive than people asked for only 6.
Availability Heuristic examples
After heavily reported plane crashes, many people judge flying to be more dangerous than driving, even though per mile traveled driving is far riskier.
- Money: flood-insurance take-up in US communities jumps in the year after a flood and then drifts back down over the following years as the memory fades (Gallagher, 2014).
- Money: in hypothetical choices, people were willing to pay more for flight insurance covering death from terrorism than for a policy covering death from any cause — which includes terrorism (Johnson, Hershey, Meszaros & Kunreuther, 1993).
- Health: people overestimate deaths from dramatic, heavily reported causes such as tornadoes and accidents, and underestimate quiet killers such as diabetes and stroke (Lichtenstein et al., 1978).
- Everyday life: after news coverage of a shark attack, beachgoers worry about being bitten while giving less thought to far more common dangers such as drowning.
- Work: managers rate employees on the incidents they remember from the last few weeks rather than on the whole year.
- Home: when spouses separately rate their share of household tasks, each tends to claim more responsibility than the other partner gives them, because their own efforts come to mind more easily (Ross & Sicoly, 1979).
- Investing: after a market crash dominates the headlines, another crash can feel more likely than the long-run record suggests.
- Everyday life: after a friend's phone is stolen, theft starts to seem common in your neighborhood, though nothing about the actual rate has changed.
How to avoid the availability heuristic
- Look up the base rate. Before judging a risk, find how often it actually happens rather than relying on the examples you remember.
- Ask why an example comes to mind. If it is recent, dramatic or heavily covered, it is probably over-represented in memory.
- Keep records. Performance logs, incident databases and decision journals beat memory for anything you will judge later.
How to design for it (nudge strategy)
Counter vivid anecdotes with concrete base rates presented as natural frequencies (e.g. '1 in 10,000'), and make rare-but-important risks memorable with a specific, relatable story.
Ethical use: design for choices people would endorse on reflection — a nudge, not sludge. Be transparent and keep opting out easy.
Key studies
Introduced the availability heuristic and showed it biases judgments of frequency, for example in the letter-K task.
Tversky, A., & Kahneman, D. (1973). Availability: A heuristic for judging frequency and probability. Cognitive Psychology, 5(2), 207–232. DOI →
Set out availability alongside representativeness and anchoring as the three core heuristics.
Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124–1131. DOI →
People overestimated dramatic, well-publicized causes of death and underestimated common, undramatic ones.
Lichtenstein, S., Slovic, P., Fischhoff, B., Layman, M., & Combs, B. (1978). Judged frequency of lethal events. Journal of Experimental Psychology: Human Learning and Memory, 4(6), 551–578. DOI →
Struggling to recall many examples made people judge the category as smaller — ease of recall, not number recalled, drove the judgment.
Schwarz, N., Bless, H., Strack, F., Klumpp, G., Rittenauer-Schatka, H., & Simons, A. (1991). Ease of retrieval as information: Another look at the availability heuristic. Journal of Personality and Social Psychology, 61(2), 195–202. DOI →
Spouses and team members each claimed more responsibility for joint activities than their partners gave them, because their own contributions were easier to recall.
Ross, M., & Sicoly, F. (1979). Egocentric biases in availability and attribution. Journal of Personality and Social Psychology, 37(3), 322–336. DOI →
Flood-insurance take-up rose sharply in the year after a local flood and then steadily declined back toward its earlier level.
Gallagher, J. (2014). Learning about an infrequent event: Evidence from flood insurance take-up in the United States. American Economic Journal: Applied Economics, 6(3), 206–233. DOI →
Key research
- Memory, Attention, and ChoicePedro Bordalo, Nicola Gennaioli, Andrei Shleifer · The Quarterly Journal of Economics (2020)
Related biases
Availability Heuristic: frequently asked questions
What is the availability heuristic?
The availability heuristic is judging how common or likely something is by how easily examples come to mind. Vivid, recent or widely reported events therefore seem more frequent than they are.
What are some examples of the availability heuristic?
Fearing flying more than driving after news of a plane crash; buying flood insurance right after a flood and letting it lapse a few years later; overestimating crime rates after a run of crime stories, even when statistics show the risk is low or falling.
Who came up with the availability heuristic?
Amos Tversky and Daniel Kahneman introduced it in a 1973 paper and included it in their influential 1974 Science article on heuristics and biases.
What is the difference between the availability heuristic and the representativeness heuristic?
Availability judges likelihood by how easily examples come to mind; representativeness judges it by how similar something is to a typical case or stereotype.
Cite this page
Raja, P. (Ed.). (2026, 8 Oct 2026). Availability Heuristic. Behavioral Economics Lab. https://www.behavioraleconomicslab.com/biases/availability-heuristic