What is the belief perseverance phenomenon?

Belief perseverance is a psychological phenomenon in which people hold on tightly to their beliefs regardless of convincing evidence that proves they are actually incorrect. This term was coined by social psychologists Ross, Lepper and Hubbard.

The social psychologists who coined the term found that some people have a tendency to cling to their foundational premises even in the face of facts that point to their inaccuracy. For example, the Jonestown cult members pledged their loyalty to Jim Jones by selling all they owned and following him. They remained devoted to him even through consistent manipulation and abuse. They even committed mass suicide at his request.