All countries have national myths. The story of the first Thanksgiving, for example, evokes the warm glow of intercultural contact: European settlers, struggling to survive in the New World, and Native American tribes eager to help. As many of us learned in history class, this story leaves a lot out. This week on Hidden Brain, we explore a national secret: that from the time Christopher Columbus arrived in the New World until 1900, there were as many as five million Native American people enslaved. We’ll learn about this history, and the psychological forces that kept it unexamined for so long.