Both make you misjudge how likely something is, but base-rate neglect ignores the statistics you already have, while the availability heuristic substitutes memory for statistics you never had.
| Base rate neglect | The availability heuristic | |
|---|---|---|
| What it is | Ignoring the general statistical rate | Judging likelihood by how easily examples come to mind |
| The error | A vivid detail overrides the base rate | Recent or dramatic examples feel more common than they are |
| Example | Trusting a positive test over a disease's low real prevalence | Fearing a plane crash right after seeing one in the news |
If you have the actual statistics and still weight a specific story more heavily, that's base-rate neglect. If you never had the statistics and are estimating from what comes to mind, that's the availability heuristic. Base-rate neglect ignores the numbers; the availability heuristic substitutes for them.
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