It is common to find polarized communication networks on social media expressing situations of extremism, separation, rupture, etc. This means that the information is produced in a kind of closed system or echo chamber. Polarization denotes the existence of groups or communities where interaction berween similar users occurs, for example in the case of people who share the same points of view […], meaning that the content that is most shared is that which reinforces the ideologies and information inside those communities.
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The ideological effect of the echo chamber is based on both homophily (similarity) and heterophily (dissimilarity), if we think of the two extremes of a social structure (the complete community or a complete network). In this way, if ideological discourses or orientations are repeated inside each echo chamber (or subcommunity), the discourses – being ideologically similar – resonate, and the discourses are reproduced and reinforced within each online community, resulting in a non-dialogue between communities. This can lead to extremism, depending on the topics […]. Once a community built upon a shared ideology is detected, it is technically easy to inject harmful or fake content into it through social bots or other strategies, in order to promote division within society at large. This currently occurs in several spheres of social media through the spread of disinformation, fake news, videos or pictures with false information, and so on.
– ‘Social network analysis, social big data and conspiracy theories’, in Routledge Handbook of Conspiracy Theories (2020), pp. 139-40