Self-organizing social hierarchies in a timid society

Emergence of hierarchies is investigated by Monte Carlo simulation in a timid society where all individuals are pacifist. The self-organiztion of hierarchies is shown to occur in two steps as the population is increased, i.e. there are three states, one egalitarian and two hierarchical states;the transition from the egalitarian to the first hierarchical state is continuous and the transition from the first hierachical state to the second one is discontinuous. In the first hierarchical society, all individuals belong to either middle class or losers and no winners appear. In the second hierarchical society, many winners emerge and the population of the middle class is reduced. The hierarchy in the second hierarchical society is stronger than the hierachy in a no-preference society studied by Bonabeau et al [ Physica A{\bf 217}, 373 (1995)]