Group identity is a central concept in many social science disciplines. We investigate why people identify with groups and show favoritism to in-group members. We anticipate group identifications are substantially influenced by genes and social environments, likely working through stable personality traits.
Using twin study data from the National Survey of Midlife Development in the United States (MIDUS I), we investigate the heritability of in-group identification and favoritism, as well as the extent to which the genetic bases of these orientations are shared with genetic underpinnings of personality traits, primarily focusing on the “Big Five”: openness to experience, conscientiousness, extraversion, agreeableness, and emotional stability/neuroticism.
Group identification is largely attributable to genetic factors. However, environments also affect group identification. The heritability of personality traits accounts for a modest portion of the genetic variation of group identification.
Our findings have implications for the study of collective action, identity politics, and the growing research program investigating social and political behavior genetics.