Sociophysics and the Forming of Public Opinion: Threshold versus Non Threshold Dynamics

A two state model for opinion forming, which has proven heuristic power, is reviewed with a novel emphasis on the existence or absence of a threshold for the dynamics. Monitored by repeated small groups discussions floater agents update their opinion according to a local majority rule. A threshold makes the initial supports to flow towards eitheir one of two opposite attractors with only one single opinion. While odd sizes yield a threshold at fifty percent even sizes, which allow the inclusion of doubt at an opinion tie, produces a threshold shift toward either 0 or 1 giving rise to minority opinion spreading. Considering heterogeneous agents like contrarians and inflexibles turn the dynamics threshold less beyond sone critical values. One unique attractor at fifty-fifty drives then the dynamics. In addition inflexibles can generate asymmetry and if one sided they erase the threshold ensuring the associated opinion to eventually gain the all population support. It may shed a new and counter intuitive light on some social aspect of the global warming phenomenon.