The Intergroup Prisoner’s Dilemma with Intragroup Power Dynamics (IPD^2) is
a new game paradigm for studying human behavior in conflict situations. IPD^2 adds the
concept of intragroup power to an intergroup version of the standard Repeated Prisoner’s
Dilemma game. We conducted a laboratory study in which individual human participants
played the game against computer strategies of various complexities. The results show that
participants tend to cooperate more when they have greater power status within their
groups. IPD^2 yields increasing levels of mutual cooperation and decreasing levels of
mutual defection, in contrast to a variant of Intergroup Prisoner’s Dilemma without
intragroup power dynamics where mutual cooperation and mutual defection are equally
likely. We developed a cognitive model of human decision making in this game inspired
by the Instance-Based Learning Theory (IBLT) and implemented within the ACT-R
cognitive architecture. This model was run in place of a human participant using the same
paradigm as the human study. The results from the model show a pattern of behavior
similar to that of human data. We conclude with a discussion of the ways in which the
IPD^2 paradigm can be applied to studying human behavior in conflict situations. In
particular, we present the current study as a possible contribution to corroborating the
conjecture that democracy reduces the risk of wars.