Confirmation Bias.

01Overview

Confirmation bias is the mind's preference for its own past. It operates at four stages — what we seek, what we notice, how we interpret what is ambiguous, and what we remember later — and it requires no dishonesty to run, only momentum. Wason's experiments showed that even a pure logic task, stripped of any emotional stake, is solved by testing examples one expects to succeed. The phenomenon sharpens with belief: Lord, Ross and Lepper demonstrated that partisans presented with the same mixed evidence emerge more convinced of their prior position than before.

02Key theorists

Wason's 2-4-6 rule-discovery experiments in 1960 revealed that subjects test hypotheses by seeking confirmation rather than disconfirmation. Two decades later, Lord, Ross and Lepper showed the bias survives contact with strong out-group evidence — biased assimilation converts mixed data into vindication. Vallone, Ross and Lepper then demonstrated the hostile media effect: partisans watching identical coverage both came away believing it favoured the enemy.

03How it works

1. 01Selective exposure: choosing information sources and conversations that flatter existing beliefs
2. 02Selective interpretation: ambiguous evidence is read in the direction of the prior
3. 03Selective memory: confirming facts are recalled more readily and with more detail
4. 04Positive test strategy: hypotheses are tested by seeking supportive examples and overlooking disconfirmation
5. 05Biased assimilation: favourable and unfavourable evidence is processed differently, hardening the prior
6. 06Hostile media effect: neutral coverage is perceived as hostile by partisans on both sides

04Where it shows up

Investment behaviour in which positions are held far past the point where the thesis collapsed; courtrooms and investigations that lock onto a suspect early and reinterpret everything to fit; self-diagnosis from search results; entire academic schools that share vocabulary but never share a disconfirming test.

05The propaganda link

The Ministry of Truth's control of the past worked only because citizens reprocessed memory in the direction of power. Confirmation bias is the apparatus running locally — no officials are needed when the citizen does the editing.

06How to resist

• Seek disconfirmation deliberately: actively commission the case against your view and read it as sympathetically as your own
• Precommit in writing what evidence would change your mind, before the evidence arrives
• Use adversarial collaboration: agree with an opponent on a test that could decide between you, in advance
• Record predictions and outcomes to defeat memory's hindsight adjustments