Confirmation Bias

It is the tendency to seek, read and remember evidence in ways that favour what we already believe or expect. Sixty years of studies, from a number puzzle to journal reviewers and shoppers, find it again and again, and a pooled review found people choose supporting information about two times in three. Testing expected cases is often sensible, and asking for the reasons against, comparing options side by side and reasoning in a group all improve judgement.

What the report found

1. People look for agreement. Asked to test a belief, people usually seek cases that would fit it rather than cases that could rule it out.
2. Expectations shape what people see. The same performance by a child was rated higher or lower depending on a label, and identical methods were judged sounder when the results agreed with the reviewer's view.
3. It reaches everyday choices. Shoppers read new product information in favour of whichever option is ahead, and pooled studies find that people choose information that supports their view about two times in three.
4. Not all of it is an error. Testing the cases you expect to be true is often sensible, and some researchers argue the habit serves argument well. How much is flaw and how much feature is still debated.
5. The process is the fix. Warnings do little, but listing reasons against a choice, considering the opposite, reasoning in a group and short training all improve judgement.

What is inside

1. The idea and where it came from
2. The original studies, explained
3. What happened when others tested it
4. Where researchers disagree
5. What we can say with confidence

Plus a timeline of the key studies, three debates set out side by side and a table grading each common claim.

Who it is for

For marketers and product teams, managers who hire and review, researchers and analysts, and anyone who wonders why the evidence always seems to agree with them.

How we work

Evidence Reviews follow one well known idea from its origin to today: the original studies, what happened when others tested them, where researchers disagree and what we can say with confidence. Every claim is graded, and both sides of each debate are set out before we say where we stand.

Cite this report

The Why We Project (2026) Confirmation Bias: Seeing what we expect to see. Evidence Review No. 22. Dubai: Why We Tech Ltd. Available at: thewhyweproject.com