This course is an advanced seminar on the psychological underpinnings of social and political polarization of the mass public, with a focus on identity and social cognition. This course focuses primarily on intra- and intergroup relations at the group level, covering topics such as: social identity and categorization; when, why, and how "Us and Them" becomes "Us Against Them"; the effects of group identity and culture on perception, information processing, and cognition; and what this means for politics, polarization, and conflict. The course is generally useful to those in any field of study within government and politics, but especially those with an interest in understanding how identity is shaped, the power of identity to affect the way we think about and see the world, and political polarization.