Why people protest, and with whom. Motivational antecedents of extreme (vs. moderate) activism and group commitment

This dissertation investigates the psychological and social mechanisms underlying activism. The manuscript comprises three main parts. Part I focuses on the development and validation of the Young Adult–Environmental Activism Scale (YA-EAS), designed to distinguish between non-extreme and extreme forms of environmental activism. Drawing on data from participants across three Western regions, Studies 1–3 establish the psychometric validity and cross-cultural stability of the scale, while Study 4 identifies distinct motivational profiles underlying each form of activism. Part II explores how activists choose the groups through which they pursue their causes, adopting the Quest for Significance Theory as its guiding framework. Combining qualitative (Study 5) and experimental methods (Studies 6–7), this section examines how loss of personal significance, combined with group characteristics (i.e., group prestige, perceived acceptance, and individual–group value fit) shape group commitment. Finally, Part III integrates motivational and group-level perspectives, grounded in the Quest for Significance framework, to explain the emergence of extreme activism. Through an experimental study (Study 8), it shows that experiences of significance loss, when combined with exposure to group norms promoting extreme environmental actions, can heighten intentions to engage in disruptive activism. Overall, the dissertation advances understanding of activism and offers practical insights for preventing radicalization. Importantly, it also extends Significance Quest Theory (Kruglanski et al., 2022) by deepening understanding of the Collectivistic Shift Hypothesis and demonstrating the applicability of the Merit–Appreciation Model of Love to the context of activism.