Group polarization is a means of a group to generate action. To generate a group needs to reach agreed SON, and generate enough energy for action from its members. Conservative create this energy by facilitating group thinking, and creating a mood of danger to the group FFFF. The feeling of danger, is usually created by bringing evidences from extreme events and groups that threatened the wale-fare of the members of the group members. These evidence, due to group thinking are unchallenged and therefore seems real and critical. This admixture of group thinking and constructing a state of need for action in face of a generated feeling of danger is producing a state of polarization.
See Cass R. Sunstein - Why Societies Need Dissent[1], and slso this article that suggest that social networks will create increase in group polarization[2]
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