Costly punishment does not always increase cooperation

Abstract

In a pairwise interaction, an individual who uses costly punishment must pay a cost in order that the opponent incurs a cost. It has been argued that individuals will behave more cooperatively if they know that their opponent has the option of using costly punishment. We examined this hypothesis by conducting two repeated two-player Prisoner's Dilemma experiments, that differed in their payoffs associated to cooperation, with university students from Beijing as participants. In these experiments, the level of cooperation either stayed the same or actually decreased when compared with the control experiments in which costly punishment was not an option. We argue that this result is likely due to differences in cultural attitudes to cooperation and punishment based on similar experiments with university students from Boston that found cooperation did increase with costly punishment.antisocial punishment ͉ cultural effects ͉ experimental outcome ͉ Prisoner's Dilemma repeated game ͉ reputation

Effects of punishment in a mobile population playing the prisoner's dilemma game

“…Rewarding and punishing human behavior has also been tested by using sequential PD games (often called gift exchange or trust games) [43]. In other cases, the payoff matrix of the PD game has been modified in order to include three types of players: cooperators, defectors, and punishers [44]. Moreover, the use of pairwise interactions is also present in models with incentive strategies [36].…”

Reputation based on punishment rather than generosity allows for evolution of cooperation in sizable groups

“…Punishment can increase cooperation levels if there are opportunities to punish defectors, that is, decreasing a defector's immediate payoff at a personal immediate cost (Fehr & Gächter, 2002;Raihani et al, 2010;Raihani et al, 2012;Sigmund, 2007). Until recently, such costly punishment has been perceived as an evolutionary puzzle because punishers accept costs to harm others while third parties benefit from the increased cooperation levels (Dreber et al, 2008;Fehr & Gächter, 2002;Rankin et al, 2009;Sigmund, 2007;Wu et al, 2009). However, if punishers can build up a punishment reputation that affects later decisions of others, punishment can lead to long-term benefits that compensate or even outweigh the immediate costs of punishment (dos Santos et al, 2011;dos Santos et al, 2013;Hilbe & Sigmund, 2010;Hilbe & Traulsen, 2012).…”

The evolutionary significance of costly punishment is still to be demonstrated

“…The efficiency ratio of punishment is then ␣:␤ ϭ 2:3 which is far less conducive to punishment than the ␣:␤ ϭ 1:4 punishment ratio assumed by the authors (3,4). A further problem with the experimental set-up is that players can only choose between cooperating, defecting, or punishing.…”

“…In conclusion, the game settings that have been used in recent studies (3,4) on the evolutionary significance of costly punishment are problematic. It can therefore not yet be concluded that costly punishment is unlikely to evolve to increase cooperation.…”

“…A recent study by Wu et al (3) confirmed earlier conclusions (4) that costly punishment is mostly maladaptive and may have evolved for other reasons. We welcome their emphasis on cultural differences in experimental games (5), but we argue that these first tests (3,4) are not yet conclusive with regard to the functional significance of costly punishment. There are three problems: (i) the definition of ''defection'' in their Prisoner's Dilemma is problematic for studies on punishment, (ii) a closer examination of their payoff matrices reveals them to be nonconducive to punishment, and (iii) their specific game structure imposes an additional opportunity cost that further reduces the effectiveness of punishment.…”