Reciprocity, Altruism, Solidarity: A Dynamic Model

Reciprocity is a decisive behavioural rule resulting in successful co-operation or deterrence. In this paper, a dynamic model is proposed, where reciprocity is described by changes in altruistic (or malevolent) ties. Multiple steady states may exist in one of which there may be general cooperation (solidarity) and the other being one of universal malice (war of each individual against all other individuals). We apply our theory to a number of examples, illustrating that the agents’ initial preferences determine whether a steady state of solidarity, selfishness or malice will emerge.