“…In particular, news recommender systems and social media filters, by nature of their design, run the risk of insulating users from exposure to different viewpoints, creating self-reinforcing biases and "filter bubbles" that are damaging to the normal functioning of public debate, group deliberation, and democratic institutions more generally (Bozdag, 2013;Bozdag & van den Hoven, 2015;Harambam, Helberger, & van Hoboken, 2018;Helberger, Karppinen, & D'acunto, 2016;Koene et al, 2015;Reviglio, 2017;Zook et al, 2017). A closely related issue is protecting these systems from manipulation by (sometimes even small but) especially active groups of users, whose interactions with the system can generate intense positive feedback, driving up the system's rate of recommendations for specific items (Chakraborty, Patro, Ganguly, Gummadi, & Loiseau, 2019).…”