http://www.hpl.hp.com/research/idl/papers/opinion_expression/ How opinions evolve online. We performed a massive study of the dynamics of group delibera- tion among several websites containing millions of opinions on topics ranging from books to media. Contrary to the common phenomenon of group polarization observed offline, we measured a strong tendency towards moderate views in the course of time. This phenomenon possi- bly operates through a self-selection bias whereby previous comments and ratings elicit contrarian views that soften the previous opinions. Fang Wu and Bernardo A. Huberman 2008-05-15 17:00:00 ratings opinion formation polarization reviews