title: Echo Chambers: Emotional Contagion and Group Polarization on Facebook.
abstract: Recent findings showed that users on Facebook tend to select information that adhere to their system of beliefs and to form polarized groups - i.e., echo chambers. Such a tendency dominates information cascades and might affect public debates on social relevant issues. In this work we explore the structural evolution of communities of interest by accounting for users emotions and engagement. Focusing on the Facebook pages reporting on scientific and conspiracy content, we characterize the evolution of the size of the two communities by fitting daily resolution data with three growth models - i.e. the Gompertz model, the Logistic model, and the Log-logistic model. Although all the models appropriately describe the data structure, the Logistic one shows the best fit. Then, we explore the interplay between emotional state and engagement of users in the group dynamics. Our findings show that communities' emotional behavior is affected by the users' involvement inside the echo chamber. Indeed, to an higher involvement corresponds a more negative approach. Moreover, we observe that, on average, more active users show a faster shift towards the negativity than less active ones.
authors.affiliation: Laboratory of Computational Social Science, Networks Dept, IMT School for Advanced Studies, 55100 Lucca, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Del Vicario
authors.affiliation: Laboratory of Computational Social Science, Networks Dept, IMT School for Advanced Studies, 55100 Lucca, Italy.
authors.forename: Gianna
authors.initials: G
authors.lastname: Vivaldo
authors.affiliation: Laboratory of Computational Social Science, Networks Dept, IMT School for Advanced Studies, 55100 Lucca, Italy.|IUSS Institute for Advanced Study, Piazza della Vittoria 5, 27100 Pavia, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bessi
authors.affiliation: Laboratory of Computational Social Science, Networks Dept, IMT School for Advanced Studies, 55100 Lucca, Italy.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Zollo
authors.affiliation: Laboratory of Computational Social Science, Networks Dept, IMT School for Advanced Studies, 55100 Lucca, Italy.|ISC-CNR Uos "Sapienza", 00185 Roma, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Scala
authors.affiliation: Laboratory of Computational Social Science, Networks Dept, IMT School for Advanced Studies, 55100 Lucca, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Caldarelli
authors.affiliation: Laboratory of Computational Social Science, Networks Dept, IMT School for Advanced Studies, 55100 Lucca, Italy.
authors.forename: Walter
authors.initials: W
authors.lastname: Quattrociocchi
mesh_terms: D003142:Communication; D004644:Emotions; D006801:Humans; D007558:Italy; D007802:Language; D016018:Least-Squares Analysis; D012306:Risk; D012919:Social Behavior; D061108:Social Media; D060756:Social Networking