Think about the last time you did something you knew was wrong. How did you explain your actions to yourself? All of us tell stories about why we do the things we do. We justify our failures, and come up with plausible explanations for our actions. This week, Elliot Aronson explains the mental processes behind this type of self-justification, and shares how he helped develop one of the most widely-known concepts in psychology: cognitive dissonance. Humans are full of contradictions. We want to stay healthy, yet we smoke and loathe to exercise. We want to be honest, but we cheat and tell lies. In other words, we want to think of ourselves as good people, yet sometimes we don't act like it. Why is that? This week, psychologist Elliot Aronson shares his research on how we figure out those contradictions.