What is the availability heuristic?
The availability heuristic is a mental shortcut: when estimating how often something happens or how likely it is, we rely on how easily relevant examples come to mind. Amos Tversky and Daniel Kahneman named it in 1973.
- Meaning
- What comes to mind easily feels common
- Proposed by
- Tversky & Kahneman (1973)
- Upside
- Fast, usually reasonable judgments
- Pitfall
- Overestimating vivid or recent events
The classic letter-K experiment
Are there more English words that start with K, or words with K as the third letter? In Tversky and Kahneman’s study, most participants said words starting with K were more common, even though words with K in the third position are actually more numerous.
It is much easier to search memory by first letter than by third letter, so ease of recall was mistaken for frequency.
Judging causes of death
Lichtenstein and colleagues (1978) asked people to estimate how often various causes of death occur. People overestimated dramatic, heavily publicized causes such as accidents, homicide and disasters, and underestimated quiet killers such as diabetes and stroke.
| Tended to be overestimated | Tended to be underestimated |
|---|---|
| Accidents, homicide, floods, tornadoes | Diabetes, stroke, some cancers |
Everyday examples
- After news of a plane crash, people choose to drive, even though driving carries more risk per mile traveled.
- Insurance: purchases rise right after people hear about a major accident or disaster nearby.
- Investing: when a stock’s big gains are all over the news, investors overestimate the chance it will keep rising.
- Group projects: each member remembers their own work vividly and overestimates their share of the effort.
Availability vs. anchoring
| Aspect | Availability heuristic | 앵커링 효과 | Anchoring effect |
|---|---|---|---|
| Cue used | Ease of recalling examples | An initial number (the anchor) | |
| Typical error | Overestimating dramatic events | Adjusting too little from the anchor |
Seeking out only information that fits what you already think is covered in misinformation and confirmation bias.
How to reduce the bias
- Check the base rate. Look up statistics rather than asking how often you’ve heard about it.
- Consider counterexamples. Deliberately think of cases on the other side.
- Keep records. Decisions based on records rather than memory are less swayed by recent events.
Frequently asked questions
- What is the availability heuristic?
- It is a mental shortcut in which people judge the frequency or probability of an event by how easily examples come to mind.
- What is an example of the availability heuristic?
- Feeling that flying is more dangerous than driving after seeing news coverage of a plane crash is a classic example.
- Is the availability heuristic always bad?
- No. It usually gives quick, reasonable answers, but it can distort judgment when some events are especially vivid, recent or heavily reported.
References
- Tversky, A., & Kahneman, D. (1973). Availability: A heuristic for judging frequency and probability. Cognitive Psychology, 5(2), 207–232.
- 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.