Emotional contagion and group polarization: experimental evidence on Facebook

Information, rumors, debates shape and reinforce the perception of reality and heavily impact public opinion. Indeed, the way in which individuals influence each other is one of the foundational challenges in several disciplines such as sociology, social psychology, and economics. One of the most fascinating and powerful mechanisms of social contagion is that of group polarization. The phenomenon manifests when like-minded people discuss and reinforce their shared views thus ending up in a more extreme position. The core of the research work presented in this thesis explores the phenomenon of group polarization on online social media. We focus on the Italian and US pages providing scientific and conspiracy information and we analyze a) users’ emotional dynamics and b) their response to dissenting information. We offer tight quantitative evidence about the existence of echo chambers on online social media. Users tend to promote their beliefs and to form highly polarized groups. Furthermore, dealing with untrusted opponents in online discussion results for users in a major commitment with respect to their own echo chamber.