Jennifer Ouellette in Ars Technica:
Social perception bias is best defined as the all-too-human tendency to assume that everyone else holds the same opinions and values as we do. That bias might, for instance, lead us to over- or under-estimate the size and influence of an opposing group. It tends to be especially pronounced when it comes to contentious polarizing issues like race, gun control, abortion, or national elections.
Researchers have long attributed this and other well-known cognitive biases to innate flaws in individual human thought processes. But according to a paper published last year in Nature Human Behaviour, social perception bias might best be viewed as an emergent property of our social networks. This research, in turn, could lead to effective strategies to counter that bias by diversifying social networks.