Search can become selective
People may ask questions, choose sources and use search terms that are more likely to produce supporting answers.
The same evidence is judged differently
Weak evidence may seem persuasive when it supports a preferred belief, while stronger opposing evidence receives unusually severe criticism.
Memory favours confirmation
Supporting examples are often easier to recall than failed predictions and contradictory cases.
Ambiguity is interpreted defensively
Unclear events can be explained in ways that preserve an existing political, religious or personal belief.
Social groups reinforce the bias
Communities may reward agreement and treat disagreement as ignorance, betrayal or moral failure.
Intelligence does not remove the problem
Greater reasoning ability can sometimes help people construct more sophisticated defences of conclusions they already prefer.
Structured methods can reduce bias
Actively seeking disconfirming evidence, stating what would change one's mind and using consistent standards can improve judgement.
Evidence notes
Possible signs include one-sided source selection, unequal evidential standards, unfalsifiable explanations, remembering only successful predictions and hostility toward corrective information.
Ethical questions
What evidence would cause me to change my mind?
Do I examine supportive and opposing claims by the same standard?
Have I actively looked for the strongest alternative explanation?
Conclusion
Confirmation bias misleads by making preferred beliefs feel better supported than they are. It cannot be eliminated completely, but transparent standards and deliberate exposure to contrary evidence can reduce its influence.