FoMind
Right after reading news of a plane crash, many people feel flying is too dangerous and would rather drive long distances. Yet per kilometer traveled, the risk of dying in a plane is far lower than in a car.
This is the availability heuristic: we judge how common something is by how easily examples come to mind. The easier to recall, the more common it seems.
What makes examples easy to recall
- Vividness: plane crashes, shark attacks, and house fires all come with strong mental images.
- Recency: something from last week surfaces more easily than something from three years ago.
- Heavy coverage: events pushed repeatedly by news and social media.
- Personal experience: if a friend just got laid off, it feels like "everyone is getting laid off right now."
None of these have much to do with how often things actually happen, yet they genuinely shape your probability judgments.
What it looks like in forecasting
- After seeing several friends post that they got into grad school, you overestimate the admission rate.
- After one food delivery arrived an hour late last month, you overestimate the chance the next one will be late.
- When headlines are full of a stock-market crash, you overestimate the chance of another sharp drop next month.
How to guard against it when forecasting
- Look for data, not examples: replace the cases that pop into your head with statistics and base rates.
- Ask: "Am I thinking of this because it's common, or because it happened to be in the news or happened to someone I know?"
- Think of the counterexamples: how many uneventful cases never made the news?
How to spot it in a review
Look back at your reasons: did your probability come mainly from one or two recent events, a viral news story, or a friend's experience, without you checking the overall data? If so, the availability heuristic may have played a part.
Easy to recall doesn't mean common: estimate probabilities from data, not from the examples in your memory.