  We review the opinion dynamics in the computer models of Deffuant et al. (D),
of Krause and Hegselmann (KH), and of Sznajd (S). All these models allow for
consensus (one final opinion), polarization (two final opinions), and
fragmentation (more than two final opinions), depending on how tolerant people
are to different opinions. We then simulate the reactions of people to ex treme
events, in that we modify the opinion of an individual and investigate how the
dynamics of a consensus model diffuses this perturbation among the other
members of a community. It often happens that the original shock induced by the
extreme event influences the opinion of a big part of the society.
