── ── Cognitive bias
Availability Heuristic
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.
How it works
Step 1 — Specify the estimate: probability/frequency being estimated · current intuitive estimate · basis (memory/news/data) · decision that depends on it.
Step 2 — Identify the reference class: population of comparable cases · size · time horizon · inclusion/exclusion criteria. (Getting this wrong is the main failure mode.)
Step 3 — Get the base rate: actual frequency in the reference class · source · confidence level.
When to use it
- user says 'we keep hearing about X so it must be common', 'that just happened so it's risky', 'the news is full of stories about this', 'I've seen this a lot lately so it's probable', or is making a risk/frequency estimate driven by memorable examples rather than data
When not to use it
the available evidence is genuinely representative of the reference class; the decision warrants heavy precautionary weight on rare but catastrophic/irreversible risks.
Worked example
Tversky and Kahneman's 1973 Availability Studies
The 1973 paper "Availability: A heuristic for judging frequency and probability" was the second in Tversky and Kahneman's seminal 1972-1974 trilogy on judgmental heuristics (the others being representativeness in 1972 and anchoring in 1974). Together with their 1974 Science paper "Judgment under Uncertainty," the work established the empirical foundation of behavioral economics — and earned the 2002 Nobel Memorial Prize in Economics.
Install this skill (free, MIT)
npx skills add deciqAI/knowledge-skills