How different or similar are out- and in-group supporters? A literature review of perceptions of differentness and similarity

Horizontal affective polarization and vertical political dissatisfaction are two main and pressing problems representative democracies are wrestling with. A growing body of work has started looking into drivers of these phenomena, yet we argue that one understudied driver of these phenomena are, what we call, citizens’ perceptions of differentness/similarity or (dis)similarity (PoDS). We define PoDS as “citizens’ perceptions that politically other- or like-minded citizens and politicians are different and/or similar from themselves with regard to attributes not obviously political in nature”. The PoDS concept already adds to the study of ingroups versus outgroups for two reasons. Firstly, it introduces non-political characteristics (e.g., how we perceive someone’s socioeconomic status but also someone’s lifestyle, hobbies, experiences or likes and dislikes) as a source of partisan dislike and even conflict towards outgroup members and their leaders. Secondly, it allows for the examination of the under-studied perception of similarity of an individual with the members of his or her political ingroup. The present literature review serves to situate this recently conceived concept in the recent relevant literature in political science in two parts. The first part of this paper addresses the most relevant literature on citizens' tendency to infer non-political traits and characteristics of other- and like-minded citizens based on the latter's vote choice. The second part of the review addresses the most relevant recent literature in social and political psychology that examine citizens' tendency to perceive politically like-minded citizens as similar to themselves, and politically other-minded citizens as different from themselves. The two final goals of this review are to examine whether the PoDS concept can be differentiated from related concepts that at first glance may appear very similar, such as othering, social sorting, stereotyping, or in- and out-group categorization, and others; and to ultimately situate this new concept within that existing literature.