Confirmation Bias is the tendency of the researcher to focus on, remember, and use information that confirms a preconceived belief. This is a broader class of bias. Other specific biases that affect researchers are Experimenter’s or Expectation Bias and Observer-expectancy Effect.

Confirmation Bias is one of the most frequent biases I see in product teams and one I am constantly watchful for in myself as a UX practitioner and when doing research. This bias is particularly dangerous for the research and ideation phases because of the massive long term impact decisions in these phases have.

Examples of Confirmation Bias

• With products when stakeholders focus only on opinions that support the feature over data and research that disputes the feature.
• Searching for articles and data that supports a belief, instead of trying to gather data against a belief.
• User research that only focuses on expected use cases.
• Leading questions when performing customer research. "Would you use X when Y happens?" "What are 3 things you hate about our product?"
• Research planning that focuses on proving a hypothesis instead of disproving the hypothesis.