The evolution of metanorms: quis custodiet ipsos custodes?

How are norms maintained? Axelrod (in Am. Political Sci. Rev. 80(4): 1095–1111, 1986) used an evolutionary computational model to proffer a solution: the metanorm (norm to enforce norm enforcement). Although often discussed, this model has neither been sufficiently replicated nor explored. In this paper we replicate and extend that model. Results were generally supportive of the original. Speculations in the original regarding the requirement to link sanctions underlying the metanorm structure were not supported, as differentiating punishment likelihoods against defectors from punishment likelihoods against shirkers (non-enforcers of the norm against defection) lead to more efficient and effective sanctioning structures that allowed norm emergence. Replications of the Groups game (two groups differing in numbers and power) generally supported the original reports, but true norms against defection emerged only if sanctioning structures were differentiated, resulting in the Strong group developing a dominant norm against others defecting (Metavengeance). That is, when groups are involved with differential power, Metanorms fail unless a more sophisticated sanctioning structure (Metavengeance) is supported.