Home > Glossary > Confirmation Bias

Confirmation Bias

Confirmation Bias


Confirmation bias is our tendency to look for information that is consistent with our existing beliefs and attitudes and ignore information that conflicts with our opinions. We subconsciously seek out and are drawn to evidence that confirms our view of the world. People are very good at overlooking facts that undermine their opinions and will follow the crowd (see Herd Instinct) that most closely supports those beliefs.

In website optimization this takes the form of accepting the results of experiments that we anticipated and looking for reasons to challenge any tests that we failed to accurately predict the outcome of. To avoid confirmation bias we should be equally thorough in examining the results of A/B tests. Whether or not we expected the outcome.

Koen Smets, a behavioural change specialist, believes confirmation bias is the worst bias people are inflicted with. He suggests that we should always investigate for signs that an intervention does not work rather than accepting it did work at the first sign of success.

“The best way to combat confirmation bias, is to look for signs that the intervention does not work. Or that any positive effects are not the result of the intervention”. Koen Smets, Behavioural Change Specialist.

Finally, confirmation bias is such a difficult bias to avoid. We should always be on our guard against accepting evidence that supports our views.


Conversion marketing – Glossary of Conversion Marketing.

Cognitive biases – Why do people prefer gut instinct to research?

Over 300 tools reviewed – Digital Marketing Toolbox.


Bias icons created by Freepik – Flaticon