Judging the probability or frequency of an event by how easily instances come to mind. Vivid, recent, or dramatic events are recalled readily and are therefore over-weighted relative to their true base rate.
In intelligence analysis
- A recent high-profile attack inflates the perceived likelihood of that attack vector, while quiescent but more probable threats are under-weighted.
- Salient reporting (a single dramatic case) swamps aggregate statistical reporting in perceived importance.
- Closely related to Vividness Bias — ease of recall is driven in part by vividness.
Countermeasure
- Base-rate discipline: explicitly estimate frequencies and compare against historical baselines.
- Structured weighting of evidence (Admiralty Rating) to separate a source's vividness from its reliability.
- Maintain a track record and calibrate over time.
Related
- Cognitive Bias — the taxonomy this bias sits within
- Vividness Bias — a driver of availability
- Structured Analytic Techniques — structured weighting and checklists