Generalized prisoner's dilemma
  Prisoner's dilemma has been heavily studied. In classical model, each player chooses to either "Cooperate" or "Defect". In this paper, we generalize the prisoner's dilemma with a new alternative which is neither defect or cooperation. The classical model is the special case under the condition that the third state is not taken into consideration. 
Xinyang Deng, Qi Liu, Yong Deng
cs.GT