title: Justine effect: punishment of the unduly self-sacrificing cooperative individuals.
abstract: BACKGROUND
  Allowing players to punish their opponents in Public Goods Game sustains cooperation within a group and thus brings advantage to the cooperative individuals. However, the possibility of punishment of the co-players can result in antisocial punishment, the punishment of those players who contribute the most in the group. To better understand why antisocial punishment exists, it must be determined who are the anti-social punishers and who are their primary targets.
  
  
  METHODS
  For resolving these questions we increased the number of players in a group from usual four to twelve. Each group played six rounds of the standard Public Goods Game and six rounds of the Public Goods Game with punishment. Each player in each round received 20 CZK ($ 1.25). Players (N = 118) were rematched after each round so that they would not take into consideration opponents' past behavior.
  
  
  RESULTS
  The amount of the punishment received correlated negatively with the contribution (ρ = -0.665, p<0.001). However, this correlation was positive for players in the highest contributors-quartile (ρ = 0.254, p<0.001). Therefore, the graph of relation between the contribution given and punishment obtained was U-shaped (R2 = 0.678, p<0.001) with the inflection point near the left boarder of the upper quartile. The antisocial punishment was present in all groups, and in eight out of ten groups the Justine Effect (the positive correlation between the contribution to the public pool and the risk of suffering punishment in the subpopulation of altruistic players) emerged. In our sample, 22.5% subjects, all of them Free riders and low contributors, punished the altruistic players.
  
  
  CONCLUSIONS
  The results of our experimental game-study revealed the existence of the Justine effect--the positive correlation between the contribution to the public pool by a subpopulation of the most altruistic players, and the amount of punishment these players obtained from free-riders.
authors.affiliation: Department of Philosophy and History of Science, Faculty of Science, Charles University, Prague, Czech Republic.
authors.forename: Aleš Antonín
authors.initials: AA
authors.lastname: Kuběna
authors.affiliation: Department of Philosophy and History of Science, Faculty of Science, Charles University, Prague, Czech Republic; Department of Economics, Faculty of Social and Economic Studies, J. E. Purkyně University in Ústí nad Labem, Ústí nad Labem, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Houdek
authors.affiliation: Department of Anthropology, Faculty of Humanities, Charles University, Prague, Czech Republic.
authors.forename: Jitka
authors.initials: J
authors.lastname: Lindová
authors.affiliation: Department of Philosophy and History of Science, Faculty of Science, Charles University, Prague, Czech Republic.
authors.forename: Lenka
authors.initials: L
authors.lastname: Příplatová
authors.affiliation: Department of Philosophy and History of Science, Faculty of Science, Charles University, Prague, Czech Republic.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Flegr
mesh_terms: D000533:Altruism; D003299:Cooperative Behavior; D005716:Game Theory; D006801:Humans; D011678:Punishment; D012935:Social Justice