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Availability Heuristic

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Availability Heuristic

The availability heuristic estimates frequency or probability by the ease with which examples can be retrieved from memory. If examples come to mind quickly, the brain concludes the event is common; if retrieval is difficult, the event seems rare.

Primary source: kahneman-2011-thinking-fast-and-slow

When It Misleads

Ease of recall is influenced by factors other than actual frequency:

  • Emotional salience: vivid, scary, or unusual events (plane crashes, shark attacks) are easy to recall → over-estimated
  • Recency: recent events are more available → recent stock market crashes feel more probable than they are
  • Media coverage: widely reported events feel more common; under-reported risks (car accidents) feel less dangerous
  • Personal experience: events you have personally experienced are more available than statistically equivalent events you only heard about

Availability Cascade

A related dynamic: a story that spreads widely through media and conversation becomes increasingly “available” → judged increasingly probable → generates more coverage → more available. This is how minor risks can cascade into public panics.

Corrective

Force yourself to consider base rates: how often does this type of event actually occur? Do not rely on how easily examples come to mind.

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