Title: Bots sustain and inflate striking opposition in online social systems,
Abstract: Societies are complex systems which tend to polarize into sub-groups of
individuals with dramatically opposite perspectives. This phenomenon is
reflected -- and often amplified -- in online social networks where, however,
humans are no more the only players, and co-exist alongside with social bots,
i.e. software-controlled accounts. Analyzing large-scale social data collected
during the Catalan referendum for independence on October 1 2017, consisting of
nearly 4 millions Twitter posts generated by almost 1 million users, we
identify the two polarized groups of Independentists and Constitutionalists and
quantify the structural and emotional roles played by social bots. We show that
bots act from peripheral areas of the social system to target influential
humans of both groups, mostly bombarding Independentists with negative and
violent contents, sustaining and inflating instability in this online society.
These results quantify the potential dangerous influence of political bots
during voting processes.