Belief perseverance is the tendency to cling to an initial conception even after the evidence on which it was based has been discredited. Once a belief takes root, it resists uprooting.

Classic experiments showed that people who formed impressions of another person on the basis of feedback later told to be false continued to rate the person in line with the original feedback. The same pattern appears with social theories, political attitudes, and self-assessments. Explaining why a belief might be true seems to strengthen it; the act of generating supporting reasons creates a mental structure that survives the removal of the original data.

The phenomenon is not simple stubbornness. It reflects the way memory and reasoning operate. People recall information consistent with their beliefs more readily than inconsistent information, and they interpret ambiguous evidence in belief-confirming ways. Debiasing is possible but effortful: actively considering the opposite, or explaining how the contrary belief could be true, can reduce perseverance.

Beliefs are easier to form than to abandon. That asymmetry shapes both ordinary opinion and scientific progress.