  This study explores the geographic dependencies of echo-chamber communication
on Twitter during the Brexit referendum campaign. We review the literature on
filter bubbles, echo chambers, and polarization to test five hypotheses
positing that echo-chamber communication is associated with homophily in the
physical world, chiefly the geographic proximity between users advocating sides
of the campaign. The results support the hypothesis that echo chambers in the
Leave campaign are associated with geographic propinquity, whereas in the
Remain campaign the reverse relationship was found. This study presents
evidence that geographically proximate social enclaves interact with polarized
political discussion where echo-chamber communication is observed. The article
concludes with a discussion of these findings and the contribution to research
on filter bubbles and echo chambers.
