Can we lie to ourselves? If you are the liar, wouldn't you know the truth? In this segment, we explore the confusing and contradictory idea of self-deception. We go back to the early 70s, when psychiatrists Harold Sackeim and Ruben Gur came up with a set of embarrassing questions that they say reveal the lies we tell ourselves. Psychologist Joanna Starek tells us that swimmers who lie to themselves swim faster than those who do not. And we explore the power of self-deception to make us more successful, and happier, people.