Harris, E. A., Pärnamets, et al.
Why have citizens become increasingly polarized? The answer is that there is increasing identification with political parties —a process known as partisanship (Mason, 2018). This chapter will focus on the role that social identity plays in contemporary politics (Greene, 2002). These party identities influence political preferences, such that partisans are more likely to agree with policies that were endorsed by their political party, regardless of the policy content, and, in some cases, their own ideological beliefs (Cohen, 2003; Samuels & Zucco Jr, 2014). There are many social and structural factors that are related to partisanship, including polarization (Lupu, 2015), intergroup threat (e.g., Craig & Richeson, 2014), and media exposure (Tucker et al., 2018; Barberá, 2015). Our chapter will focus on the psychology and neuroscience of partisanship within these broader socio-political contexts. This will help reveal the roots of partisanship across political contexts.
A burgeoning literature suggests that partisanship is a form of social identity with interesting and wide-reaching implications for our brains and behavior. In some ways, the effects of partisanship mirror those of other forms of group identity, both behaviorally and in the brain. However, partisanship also has interesting biological antecedents and effects in political domains such as belief in fake news and conspiracy theories, as well as voting behavior. As political polarization rises in many nations across the world, partisanship will become an increasingly divisive and influential form of social identity in those countries, thus highlighting the urgency to understand its psychological and neural underpinnings.