This PhD dissertation tackle the surge in political polarization that many European countries are now experiencing. We commonly define political polarization as intensification of political cleavages between ideological or partisan groups on both classical economic issues and new cultural issues related to European integration, immigration, and cultural liberalism. This thesis shed light on new forms of social and political conflicts which deeply destabilize European societies nowadays; and to better understand the new cleavages among citizens since the Great Recession and the migrant crisis occurred.
Whereas most of the empirical research in Europe is focusing on the study of radicalization and its electoral outcomes, recent developments from political psychology established the deep impact of individual personality traits (such as Big Five) on political orientations and policy preferences. This dissertation offers an original three-level methodological design in order to investigate the topic of political polarization in Europe and its relationship with personality traits.

The first level of the research design analyzes political polarization in a comparative cross-national perspective, relaying on international longitudinal surveys since the beginnings of the 1980s. We assume that the evolution of political cleavages, especially along the cultural dimension, is related to the sharp increase of polarization between ideological and partisan groups. The second level is built on several national surveys in order to evaluate the intensity of the relationship between political polarization and personality traits among European publics. Here, the main hypothesis is that political polarization is generated by strengthening consistency between personality traits, political orientations, economic and social preferences.
The third level of the whole research design is derived from a laboratory experiment to enrich the results from the two other levels by adding physiological and psychometric measurement. This experiment aims to disentangle the potential interactions between personality, political orientation and policy preferences on one side, and their physiological responses on the other side. All in all, this PhD dissertation offers a theoretical and methodological approach to study polarization in Europe, combining jointly longitudinal quantitative survey data analysis at the macro level and producing original experimental data at the micro level in order to clarify how political polarization, individual personality traits and their physiological manifestations are related together. Finally, the aim of this dissertation is to shed new light on the state of polarization in the context of European political and partisan systems and on the substance of past and potential future political change in Europe.