  The hypothesis of selective exposure assumes that people seek out information
that supports their views and eschew information that conflicts with their
beliefs, and that has negative consequences on our society. Few researchers
have recently found counter evidence of selective exposure in social media:
users are exposed to politically diverse articles. No work has looked at what
happens after exposure, particularly how individuals react to such exposure,
though. Users might well be exposed to diverse articles but share only the
partisan ones. To test this, we study partisan sharing on Facebook: the
tendency for users to predominantly share like-minded news articles and avoid
conflicting ones. We verified four main hypotheses. That is, whether partisan
sharing: 1) exists at all; 2) changes across individuals (e.g., depending on
their interest in politics); 3) changes over time (e.g., around elections); and
4) changes depending on perceived importance of topics. We indeed find strong
evidence for partisan sharing. To test whether it has any consequence in the
real world, we built a web application for BBC viewers of a popular political
program, resulting in a controlled experiment involving more than 70
individuals. Based on what they share and on survey data, we find that partisan
sharing has negative consequences: distorted perception of reality. However, we
do also find positive aspects of partisan sharing: it is associated with people
who are more knowledgeable about politics and engage more with it as they are
more likely to vote in the general elections.
