Confirmation bias is the tendency to search for, interpret, and remember information in a way that confirms one’s preexisting beliefs. Counter-evidence is noticed less readily, interpreted more skeptically, or simply forgotten.

The bias appears in many settings. People testing a hypothesis tend to look for confirming instances rather than potential falsifications. Political partisans interpret the same news footage in opposite ways. Scientists are not immune; they may design studies that are more likely to support favored theories or explain away inconvenient results. Even the evaluation of one’s own personality traits shows the pattern: evidence of desired qualities is accepted more readily than evidence of undesired ones.

Confirmation bias is not deliberate dishonesty. It arises from the ordinary operations of attention, memory, and reasoning, all of which are influenced by existing knowledge structures. Awareness of the bias can reduce its effects—actively seeking disconfirming evidence, considering the opposite, or using structured decision protocols—but the tendency itself is robust and widespread.

Once a belief is in place, the mind tends to protect it. Confirmation bias is the name of that protective tendency.