Collective Action and Intra-Group Conflict: An Experiment

In many situations, two rivals find themselves facing a common threat necessitating cooperation. Such alliances are uneasy as the parties anticipate eventually competing against each other in the future. Recent theoretical work shows that both standalone and joint contribution strategies, as well as a hybrid of the two, can emerge in equilibrium where the former strategy is characterized by one of the rivals contributing enough to eliminate the common threat, while the latter is characterized by rivals providing half the necessary effort to eliminate the common threat. Using a controlled laboratory experiment, we show that player behavior is best described by the hybrid strategy. However, none of these predictions closely describes the observed behavior, which is better described as following a proportionate rule.