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Concept

Confirmation bias

We seek, interpret, and remember information in a way that confirms what we already believe.

In Spanish
Sesgo de confirmación
Origin
Wason (1960); Nickerson (1998)

What problem it addresses

Explains why it is so hard to change our minds and why research can end up seeing only what it expected.

An example

You are told the sequence 2, 4, 6 follows a rule. You can propose other sequences to discover it.

What most people do2, 4, 6Fits the rule8, 10, 12Fits the rule20, 22, 24Fits the ruleEverything confirms: “even numbers going up by 2”
They test sequences that fit their idea. They all fit, so they announce “even numbers going up by 2.”
What they should have done1, 7, 30Fits the rule3, 2, 1Does not fit5, 5, 5Does not fitThe rule: three numbers in increasing order
Test sequences that could disprove it. The rule was “three numbers in increasing order.”

Most people only tested sequences that confirmed their idea. To discover the rule, you had to look for one that disproved it.

Why it happens

  1. We form an idea very quickly.

  2. We look for cases that confirm it, not cases that test it.

  3. Each confirmation makes us more confident, even though it proves nothing.

Applications in design

  • Use it like this

    In research, deliberately look for what contradicts your hypothesis.

  • Avoid

    Designing interviews or surveys with questions that lead to the expected answer.

  • Don’t fall for it

    Before deciding, write down what evidence would make you change your mind.

6 of 29

What the research says

That is how many participants got the rule right on the first try. Most first announced some wrong rule (Wason, 1960).

Solid evidence. Nickerson (1998) reviewed decades of studies and described it as a bias present in many domains.

Connections

Used in

Related to

Authors and works

  1. 1960

    Peter Wason

    Created the 2, 4, 6 task.

  2. 1998

    Raymond Nickerson

    Reviewed the research on the bias across many domains.

Sources

Original sources

  • Wason, P. C. (1960). On the failure to eliminate hypotheses in a conceptual task. Quarterly Journal of Experimental Psychology, 12(3), 129–140. View source: Wason, P. C. (1960)

Academic reviews

Last reviewed: