Group Formation through Indirect Reciprocity
  The emergence of structure in cooperative relation is studied in a game theoretical model. It is proved that specific types of reciprocity norm lead individuals to split into two groups. The condition for the evolutionary stability of the norms is also revealed. This result suggests a connection between group formation and a specific type of reciprocity norm in our society. 
Koji Oishi, Takashi Shimada, and Nobuyasu Ito
physics.soc-ph cs.SI nlin.AO q-bio.PE