Availability Heuristic: Definition, Examples and the Original Experiments

By the IQ Revealed Team · Updated October 28, 2026

The availability heuristic is the mental shortcut of judging how common or how likely something is by how easily examples of it come to mind. If instances spring to mind quickly, the thing feels frequent; if you struggle to think of any, it feels rare. Amos Tversky and Daniel Kahneman named the shortcut in 1973. Most of the time it works, because common things really are easier to recall. It misleads you whenever something becomes memorable for a reason other than being common: it was dramatic, recent, personal or all over the news.

The availability heuristic at a glance

The question you are asked: how often does this happen, or how likely is it?
The question you answer instead: how easily can I think of an example?
When it works: when what you remember is a fair sample of what actually happens.
When it fails: when vividness, recency, media coverage or the way memory is organised make some examples easier to retrieve than their real frequency deserves.
Also called: availability bias. It is one of the classic cognitive biases, described alongside representativeness and anchoring.

The original experiments

Tversky and Kahneman introduced availability in a 1973 paper in Cognitive Psychology and summarised the key demonstrations in their 1974 article in Science. Three of them still explain the idea better than any definition.

Words that start with r

Pick a word of three letters or more at random from an English text. Is it more likely to start with r, or to have r as its third letter? People answer by trying to recall words, and it is much easier to search memory by a first letter than by a third. So most judge that words beginning with the consonant are more numerous, even for consonants such as r and k, which are more frequent in the third position. The ease of the search is mistaken for the size of the category.

Famous names

In another study, people heard a list of well-known men and women and were then asked whether the list contained more men or more women. In some lists the men were more famous; in others, the women. In each case participants wrongly judged that the sex with the more famous names had been the more numerous. Famous names were easier to recall, so they felt like more.

Committees of two and of eight

How many different committees of two people can be formed from a group of ten, and how many of eight? Mathematically the answer is the same, 45, because every committee of two leaves out a committee of eight. But small committees are easier to imagine. The median estimate was 70 for committees of two and 20 for committees of eight. Here what is available is not a memory but how easily examples can be constructed.

Ease, not just content: the 1991 twist

Is it the number of examples you recall that sways you, or the feeling of how easy it was? In 1991 Norbert Schwarz and colleagues separated the two. Some participants were asked to recall six occasions on which they had acted self-assuredly, others twelve. Six came easily; twelve was a struggle. Those who recalled twelve examples of self-assured behaviour went on to rate themselves as less self-assured than those who recalled six, even though they had just produced twice as much evidence. When recall felt hard, people concluded the behaviour could not be typical of them. When the difficulty could be blamed on something else, the effect disappeared. The judgement rests on the experience of remembering, not only on what is remembered.

Risk, news and fear

In a 1978 series of experiments, Sarah Lichtenstein, Paul Slovic, Baruch Fischhoff and colleagues asked people to judge how many deaths a year various causes produce. Their answers were consistent but systematically skewed: small frequencies were overestimated and large ones underestimated, and some causes were exaggerated while others of the same real frequency were played down. The authors traced the errors to disproportionate exposure, memorability or imaginability of particular events, and found that participants could not correct for them when explicitly told to.

Gerd Gigerenzer, at the Max Planck Institute for Human Development in Berlin, looked at a real-world case. After the attacks of 11 September 2001, many Americans avoided flying and drove instead. In the year that followed, he estimated that about 1,500 more people died on American roads than the usual baseline would predict, more than the number of passengers killed on the four hijacked flights. Gigerenzer calls this a reaction to dread risk, rare events that kill many people at once. It is a close relative of availability: a single, endlessly replayed catastrophe outweighs thousands of unreported ordinary accidents.

In medicine: the last case you saw

Doctors are not immune. In a 2010 experiment at Erasmus University Medical Centre in Rotterdam, Sílvia Mamede and colleagues first had 36 internal medicine residents evaluate a set of clinical cases. Later, the residents diagnosed new cases, some of which looked like the earlier ones but had different diagnoses. Second-year residents scored 1.55 out of 4 on the look-alike cases against 2.19 on the others: the recently seen diagnosis came to mind and was wrongly applied. First-year residents did not show the pattern. When the residents then reconsidered the look-alike cases through structured reflection, going back over the findings for and against each possible diagnosis, accuracy improved in both years.

Availability, representativeness and its neighbours

Availability is easily confused with other biases, and the difference matters for fixing it:

Representativeness judges what category something belongs to by how typical it looks, and tends to ignore base rates. Availability judges how frequent something is by how easily it comes to mind.
Recency is one route to availability: recent events are easier to recall. Tversky and Kahneman noted that the felt probability of traffic accidents rises for a while after you see an overturned car by the road. For memory for lists, see our page on the serial position effect.
Confirmation bias is about which evidence you seek and accept; availability is about which evidence your memory hands you first. The two compound: the examples you sought out are also the ones you recall.

Does a high IQ protect you?

Not in any way research has demonstrated. In 2008 Keith Stanovich and Richard West reported seven studies in which many classic thinking biases were uncorrelated with cognitive ability, including anchoring, framing, base-rate neglect and myside bias. The availability heuristic was not one of the biases they tested, so we will not claim more than that. Experience is no shield either: in the Rotterdam study it was the second-year residents, not the first-year ones, whose diagnoses were pulled towards the cases they had just seen. Knowledge supplies examples; it does not check whether those examples are representative.

That is why reasoning ability and good judgement are best treated as separate skills. Our pages on critical thinking and the Dunning-Kruger effect look at other ways capable people misjudge.

Is the availability heuristic always bad?

No. Tversky and Kahneman described their heuristics as “highly economical and usually effective”. Without a statistics table to hand, how easily you can recall examples is often the best evidence available, and most of the time it points in the right direction. The problem is narrower: it fails in predictable situations, and those are exactly the situations in which memorability and frequency come apart.

How to reduce availability bias

Count instead of recall. Before judging a risk, look up the base rate. How often a thing is reported is not how often it happens.
Ask why an example came to mind. Was it common, or was it vivid, recent, personal or widely shared?
Reflect in a structured way. In the Rotterdam study, going back over the evidence for and against each option improved accuracy after recent cases had misled people.
Do not rely on good intentions. In the 1978 risk studies, being told about the bias did not remove it. Changing the procedure works better than trying harder.
Widen the sample. In teams, ask several people for examples independently before discussing them, so one memorable story does not set the frame for everyone.

Trust and scope notes

This page summarises published research for general information, with figures taken from the studies listed below. The IQ Revealed test is an online reasoning test of 40 original items for adults aged 18 and over; it does not measure the availability heuristic or any other thinking bias, and a reasoning score says little about how well someone judges frequency and risk. Our guide to how IQ tests work explains what an online test can and cannot tell you.

IQ Revealed is not affiliated with, endorsed by or connected to the researchers, universities, institutes, journals or publishers named on this page. Names are used only to identify the research being described.

Frequently asked questions

What is the availability heuristic?＋

The availability heuristic is the mental shortcut of judging how common or how likely something is by how easily examples of it come to mind. Amos Tversky and Daniel Kahneman named it in 1973. It is usually a reasonable guide, because common things tend to be easy to recall, but anything that makes an example memorable without making it common, such as drama, recency or news coverage, distorts the judgement.

What is an example of the availability heuristic?＋

Ask people whether more English words start with the letter r or have r as their third letter. Most say first, because words are far easier to search for by their first letter, yet r and k both appear more often in the third position. In everyday life, the same shortcut makes a widely reported plane crash feel like evidence that flying is dangerous, while ordinary road deaths, which are far more common, rarely come to mind.

Is the availability heuristic the same as availability bias?＋

They are two names for the same thing seen from different sides. The heuristic is the shortcut itself, judging frequency by ease of recall. Availability bias is the systematic error the shortcut produces when ease of recall and real frequency come apart. Searchers use the two terms interchangeably.

What is the difference between the availability and representativeness heuristics?＋

Availability answers 'how often does this happen?' from how easily examples come to mind. Representativeness answers 'what kind of thing is this?' from how closely it resembles a typical case. Tversky and Kahneman described both, together with anchoring, in their 1974 article in Science. They can lead to different errors: availability distorts frequency, representativeness leads people to ignore base rates.

Are intelligent people less affected by the availability heuristic?＋

There is no good evidence that they are. In 2008 Keith Stanovich and Richard West found that a long list of classic thinking biases, including anchoring, framing and base-rate neglect, were largely unrelated to cognitive ability. The availability heuristic itself was not among the biases they tested, so the honest answer is that a high IQ has not been shown to protect against it.

How can you avoid the availability heuristic?＋

Replace recall with counting where you can: look up the base rate before you judge a risk, and ask whether an example comes to mind because it is common or because it was vivid or recent. In a 2010 study of medical residents, structured reflection, going back over the evidence for and against each diagnosis, improved accuracy after recent cases had led them astray. Simply being told to avoid the bias, on the other hand, did not help in a 1978 study of risk judgements.