Hebrew University of Jerusalem students participated in two experiments of repeated play of the Intergroup Prisoners' Dilemma (IPD) game, which involves conflict of interests between two groups and, simultaneously, within each group. The experiments manipulated the level of competition exhibited...

Repeated interaction in integroup conflict was studied in the context of two team games: the intergroup public goods (IPG) game and the intergroup prisoner's dilemma (IPD) game. The results reveal (a) a main effect for game type; subjects were twice as likely to contribute toward their group...

The intergroup prisoner's dilemma (IPD) game was played repeatedly in an attempt to distinguish the dynamic process associated with reciprocation at the intergroup level from that resulting from adaptation at the individual level. Results show that when players were not allowed to communicate...

Immanuel Kant, Adam Smith, Charles Darwin, George Williams, and Stephen J. Gould, among others, have pointed out that observing that a certain behavior causes a certain effect does not itself license the inference that the effect was the result of intent or design to bring about that effect....