Left-right Categorization and Perceptions of Party Ideologies 1 Forthcoming on Political Behavior DOI: 10.1007/s11109-018-9451-y by: Federico Vegetti (vegetti.fede@gmail.com) Daniela Širinić (dsirinic@gmail.com) Abstract Political similarities and differences are often described in terms of left and right. However, while scholars have long focused on their substantive policy content, ideological labels also serve largely as symbolic identifiers of political groups. We investigate how the contextual variation in what left and right mean relates to the way that citizens perceive party ideological positions in European countries. We discuss the impact of categorization, a basic cognitive process where people organize reality by classifying objects into groups based on some relevant characteristics. We argue that when left and right strongly reflect symbolic group attachments, citizens tend to accentuate their perceived similarity to parties in their own ideological camp, and difference from parties in the opposite ideological camp. Using data from the European Election Study 2009, we provide empirical evidence of the latter process. We conclude that taking into account the categorical function of left-right provides important insights to understand political perceptions and polarization. 1 Earlier versions of this paper were presented at the MPSA conference 2014, and at the Political Behavior Research Group (PolBeRG) seminar at the Central European University in Budapest. We thank the present and past members of PolBeRG for all the stimulating discussions over the years, in particular Levi Littvay, Zoltán Fazekas, and Martin Mölder. We also thank the Central European University for providing us and many others a great environment where to exchange ideas. Replication materials are available at https://doi.org/10.7910/DVN/MT7XU0.