Availability heuristic
The availability heuristic is the habit of judging how likely something is by how easily examples come to mind.
We judge how likely something is by how easily examples spring to mind, which means vivid and recent things seem more common than they are.
The availability heuristic is the mental shortcut of estimating the probability or frequency of something by how easily instances of it come to mind. Events that are recent, vivid, or heavily reported feel more likely, regardless of their actual frequency.
Ease of recall as a proxy
The heuristic substitutes an easy question for a hard one. Asked how common something is, a question that properly requires data, the mind instead answers how easily can I think of an example, which is quicker. Usually the two track each other, common things are easier to recall, so the shortcut works. But ease of recall is also driven by vividness, recency, and emotional impact, which have nothing to do with true frequency, and there the shortcut misleads.
Vividness beats statistics
The result is a systematic distortion toward the dramatic. People overestimate the risk of rare but memorable dangers, plane crashes, shark attacks, terrorist incidents, and underestimate common but mundane ones, household accidents, ordinary illness, that harm far more. A single vivid news story can do more to shift perceived risk than reams of statistics, because the story is available to memory and the statistics are not.
Why it matters
The availability heuristic shapes how people, markets, and governments respond to risk, often badly. Resources flow toward the frightening and recent rather than the statistically serious; investors chase whatever disaster or boom is freshest in mind; policy lurches in response to the latest vivid event. Media coverage, by determining what is available to recall, quietly steers collective judgements of what matters and what is dangerous.
The availability heuristic is a reminder that perceived risk and actual risk diverge in predictable ways, and that what is memorable is not the same as what is likely. Correcting for it means deliberately reaching for base rates and data rather than trusting the examples that the mind, fed by memory and media, serves up most readily.