title: Direct and indirect punishment among strangers in the field.
abstract: Many interactions in modern human societies are among strangers. Explaining cooperation in such interactions is challenging. The two most prominent explanations critically depend on individuals' willingness to punish defectors: In models of direct punishment, individuals punish antisocial behavior at a personal cost, whereas in models of indirect reciprocity, they punish indirectly by withholding rewards. We investigate these competing explanations in a field experiment with real-life interactions among strangers. We find clear evidence of both direct and indirect punishment. Direct punishment is not rewarded by strangers and, in line with models of indirect reciprocity, is crowded out by indirect punishment opportunities. The existence of direct and indirect punishment in daily life indicates the importance of both means for understanding the evolution of cooperation.
authors.affiliation: Department of Public Economics, University of Innsbruck, A-6020 Innsbruck, Austria; loukas.balafoutas@uibk.ac.at.
authors.forename: Loukas
authors.initials: L
authors.lastname: Balafoutas
authors.affiliation: Social Science Division, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates; and.
authors.forename: Nikos
authors.initials: N
authors.lastname: Nikiforakis
authors.affiliation: Department of Economics, University of Cologne, D-50923 Cologne, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Rockenbach
mesh_terms: D000374:Aggression; D006801:Humans; D008962:Models, Theoretical; D011678:Punishment; D014754:Violence
keywords: cooperation; field experiment; indirect reciprocity; punishment; social norms