  We present a toy model of opinion spreading in a society which combines a
self-reinforcing mechanism with diffusion. The relative strength of these two
mechanisms - called the affectability of the system - is a free parameter of
the model. The model is run on a scale-free network and its asymptotic
behaviour is investigated. A surprising emergent effect is observed: If every
individual becomes more attentive to the opinions of others, the society as a
whole switches from a plurality of nuanced opinions into the state of an
absolute consensus on an extreme opinion. This counter-intuitive emergent
behaviour may help to explain certain paradoxes in human history.

Physics and Society;Social and Information Networks