People lie. We tell Aunt Linda we like her new hat. We tell a creditor that the check is in the mail. And we don't just lie to others, we lie to ourselves: Those extra pounds look good on me. I can quit smoking anytime I want—I just don't want to. Because we are liars, simply asking people what their innermost thoughts are can produce inaccurate results. This is particularly true for sensitive topics such as racism and bigotry. Psychologists and pollsters have long known that people will offer self-serving answers to questions about such topics and will act in ways that reveal latent biases.
(Daniel Levitin, professor of psychology and neuroscience at McGill)