# Hindsight bias

*Also called: Knew it all along effect*

- **Cluster:** Causal errors — Sequence, coincidence and hindsight read as cause
- **Page:** https://fallacy.wiki/fallacy/hindsight/
- **In Arabic:** https://fallacy.wiki/ar/fallacy/hindsight.md
- **Licence:** CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/

## What it is

Treating an outcome as having been obvious once you know it happened.

## In the wild

> The crash was obvious, anyone could have seen it coming.

## How to answer it

Ask what was actually written down or predicted before the event.

## Origin and naming

Documented experimentally by psychologist Baruch Fischhoff in 1975, who showed that people told an outcome inflate how predictable it was beforehand — the 'knew-it-all-along phenomenon', also called creeping determinism. It is less an argument than a memory defect that sounds like one.

## More places it shows up

- After the election: 'Obviously the underdog was going to win — the signs were everywhere.' Before it: nobody circled those signs.
- The startup folded and suddenly every investor says the business model was doomed from day one.
- After the layoff announcement, everyone on the team 'always suspected' the company was in trouble.
- The bridge collapsed and now every commenter is an engineer who saw the fatigue cracks years ago.

## How to spot it

- The certainty is always backward-facing — ask what they said before, and the record is thin.
- Nobody can point to a prediction made in advance, only to 'signs' noticed afterward.
- The same people who 'knew it' are freshly surprised by the next event.

## Nearby

- [Historian's fallacy](https://fallacy.wiki/fallacy/historians.md)
- [Regression fallacy](https://fallacy.wiki/fallacy/regression.md)
- [Texas sharpshooter](https://fallacy.wiki/fallacy/texas-sharpshooter.md)
- [Just-world fallacy](https://fallacy.wiki/fallacy/just-world.md)

## Read more

- [Wikipedia](https://en.wikipedia.org/wiki/Hindsight_bias)

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From fallacy.wiki — a bilingual field guide to 91 logical fallacies, published by phi holdings. Licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/): reuse freely with attribution to fallacy.wiki.