Confirmation bias

Confirmation bias is a well-documented phenomenon in cognitive science. Once we have formed an opinion, we unconsciously place more weight on information that supports it—and less on information that contradicts it. This applies to everything from the news stories we click on to how we remember past discussions. This effect isn't a result of dishonesty or laziness, but rather a way for the brain to conserve energy by protecting its existing models of the world. Consequently, opinions become reinforced over time, even when the underlying evidence is weak.

You suspect a colleague doesn't like you. The next time they give a brief answer, you interpret it as proof. When they smile at you, you don't assign much importance to it. After a week, your suspicion feels confirmed—even though their behavior has been neutral all along.

This phenomenon influences everything from science to politics and relationships. Recognizing it in yourself is one of the most powerful intellectual skills because it allows you to update your beliefs more reliably.

Confirmation bias isn't about deliberately lying to yourself. It happens automatically, often even to the most well-read and intelligent people.