Availability Heuristic

Overview

The availability heuristic: people estimate probability by how easily examples come to mind. Vivid, recent, and media-reported events are systematically overestimated; routine, statistical events are underestimated. Five triggers: recency, vividness, media coverage, personal experience, imaginability. Structural fix: reference-class forecasting — answer from base-rate data, not memory.

Composes with bayesian-reasoning, probabilistic-thinking, anchoring, survivorship-bias, framing-effect.

When to Use

• Someone estimates probability from memorable examples rather than data
• Risk perception driven by recent news, vivid anecdotes, or media coverage
• Team is preparing for the last disaster rather than the most likely next one
• Investment or resource-allocation decision follows a recent dramatic event
• Medical, legal, or technical decision made by anecdote rather than reference class
• AI capex, AI valuations, or AI-adoption/displacement estimates are driven by a viral demo, a dramatic layoff headline, or a safety scare rather than deployment and labor base rates

Not when: available evidence is a representative sample; decision warrants precautionary weight on rare catastrophic risks; no reference-class data exists.