Partisan Blocking: Biased Responses to Shared Misinformation Contribute to Network Polarization on Social Media

Researchers know little about how people respond to misinformation shared by their social media “friends.” Do responses scale up to distort the structure of online networks? We focus on an important yet under-researched response to misinformation—blocking or unfollowing a friend who shares it—and assess whether this is influenced by political similarity between friends. Using a representative sample of social media users (n = 968), we conducted two 2 × 2 between-subjects experiments focusing on two political issues and individuals’ political ideology as a quasi-factor. The first factor manipulated who shared the misinformation (politically similar vs. dissimilar friend); the second manipulated the misinformation’s plausibility (implausible vs. moderately plausible). Our findings, which replicated across political issues and levels of plausibility, reveal that social media users, particularly left-wing users, are more likely to block and unfollow politically dissimilar than similar friends who share misinformation. Partisan blocking contributes to network polarization on social media.