“A man with a conviction is a hard man to change,” Festinger, Henry Riecken, and Stanley Schacter wrote in
When Prophecy Fails, their 1957 book about this study. “Tell him you disagree and he turns away. Show him facts or figures and he questions your sources. Appeal to logic and he fails to see your point … Suppose that he is presented with evidence, unequivocal and undeniable evidence, that his belief is wrong: what will happen? The individual will frequently emerge, not only unshaken, but even more convinced of the truth of his beliefs than ever before.”
This doubling down in the face of conflicting evidence is a way of reducing the discomfort of dissonance, and is part of a set of behaviors known in the psychology literature as “motivated reasoning.” Motivated reasoning is how people convince themselves or remain convinced of what they want to believe—they seek out agreeable information and learn it more easily; and they avoid, ignore, devalue, forget, or argue against information that contradicts their beliefs.