Definition
Confirmation bias is the tendency to seek out, notice, and remember evidence that fits what one already believes — while overlooking, dismissing, or forgetting evidence that does not. It operates quietly, shaping which facts a person even registers, long before any conscious reasoning takes place.
It is not the same as deliberately lying or arguing in bad faith. Confirmation bias feels like honest inquiry from the inside: the person genuinely believes they are weighing the evidence, when in fact they have been collecting only one side of it.
Why it matters
How it works
Confirmation bias acts at three points. When gathering information, people search where supporting evidence is likely to be found. When interpreting ambiguous information, they read it in the direction of their belief. When recalling it later, supporting instances come to mind more readily than contradicting ones.
Together these stages create a sealed loop: a belief generates a biased sample of evidence, the biased sample appears to confirm the belief, and confidence grows. This is why simply being careful or well-intentioned is not enough — the bias corrupts the inputs. The only reliable counter is to actively hunt for the best case against your own position.