The way digital information technologies work and, more specifically, the possibilities for action that technological devices offer to us affect our processes of political belief formation. In particular, there seems to be a close connection between our digital affordances and the increase of the sort of polarization that threatens the proper functioning of democracy. In this paper, we analyze whether the type of polarization linked to the use of digital technologies, and which endangers the health of public deliberation, has to (...) do with the adoption of beliefs whose contents are increasingly extreme—extremism—or, on the contrary, has more to do with increasing our credence in the core beliefs of our political identity—radicalism. (shrink)