Third-party punishment

Third-party punishment, or altruistic punishment, is punishment of a transgressor (first party) which is administered, not by a victim of the transgression (second party), but rather by a third party not directly affected by the transgression. It has been argued that third-party punishments are the essence of social norms, as they are an evolutionarily stable strategy, unlike second-party punishments. It has also been shown that third-party punishments are exhibited in all examined populations, though the magnitude of the punishments varies greatly, and that costly punishment co-varies with altruistic behavior. Differences between within-group and inter-group altruistic punishments have also been observed.