Nowadays, social media platforms, online blogs, and discussion forums are a crucial component in the public sphere, fostering discussions and influencing the public perception for a myriads of social issues such as politics, security, climate, health, economics, migration, to name but a few. On the one hand, this represents an unprecedented opportunity to discuss and propose new ideas, giving voice to the crowds. On the other hand however, new socio-technical issues arise, which are related to the discussion of such controversial topics. Among the most pressing issues in online societal debates, is the formation of so-called “echo chambers”, i.e., situations where polarized like-minded people reinforce each other’s opinion, but do not get exposed to the views of the opposing side. Echo chambers have a negative effect on society since polarized communities tend to get isolated and only marginally exposed to unbiased information.

As a result, people belonging to echo chambers are more likely to incur in extremization and hate. Unfortunately, misinformation is present also outside of echo chambers. Indeed, rumor spreading, fake news, and hoaxes are another major issue of all controversial social discussions, where people try to influence the opposing side with questionable means. Misinformation and political campaigns are sometimes also carried out by groups of automated accounts that pollute and tamper the social environment by injecting a large number of targeted messages. This special session focuses on data science approaches to study, model, characterize, and propose solutions to these, and other similar, challenges related to all aspects of polarized, political, and controversial societal debates.