Oxytocin Promotes Altruistic Punishment

Gökhan Aydogan; Nadja C. Furtner; Bianca Kern; Andrea Jobst; Norbert Müller; Martin G. Kocher

Disclosures

Soc Cogn Affect Neurosci. 2017;12(11):1740-1747. 

In This Article

Abstract and Introduction

Abstract

The role of neuromodulators in the enforcement of cooperation is still not well understood. Here, we provide evidence that intranasal applied oxytocin, an important hormone for modulating social behavior, enhances the inclination to sanction free-riders in a social dilemma situation. Contrary to the notion of oxytocin being a pro-social hormone, we found that participants treated with oxytocin exhibited an amplification of self-reported negative social emotions such as anger towards free-riders, ultimately resulting in higher magnitude and frequency of punishment of free-riders compared to placebo. Furthermore, we found initial evidence that oxytocin contributes to the positive effects of a punishment institution by rendering cooperation preferable in the oxytocin condition for even the most selfish players when punishment was available. Together, these findings imply that the neural circuits underlying altruistic punishment are partly targeted by the oxytonergic system and highlight the importance of neuromodulators in group cohesion and norm enforcement within social groups.

Introduction

Oxytocin constitutes one of the most important neuromodulators of social behavior among mammals, including humans. The evidence on its exact mechanisms of action, however, is still inconclusive. Several studies have found that the neuropeptide oxytocin modulates various behaviors associated with pro-social behavior (Kosfeld et al., 2005; Israel et al., 2009; Mikolajczak et al., 2010; Israel et al., 2012), including conflict resolution (Ditzen et al., 2009), in-group conformity (Stallen et al., 2012) and both cognitive and emotional empathy ( Domes et al., 2007; Rodrigues et al., 2009, Guastella et al., 2010; Schulze et al., 2011; Shamay-Tsoory et al., 2013). It is these characteristics that have led to the common interpretation of oxytocin (henceforth OT) as a 'pro-social' hormone (MacDonald and MacDonald, 2010, Ebitz et al., 2013). This notion, however, has recently been questioned due to contradictory findings regarding the effects of inhaled OT on pro-social preferences. For instance, a recent systematic review of the oxytocin literature found no evidence that trust behavior is associated with oxytocin (Nave et al., 2015). Specifically, these authors found that trust was neither influenced by inhaled OT, nor by OT plasma levels nor by any genetic polymorphisms of the OT receptor gene.

Moreover, several recent studies indicate a more contextual effect of OT on social behavior, since OT has been shown to promote cooperation within groups but not between them (Dreu et al., 2010), to enhance a general ethnocentric bias (De Dreu et al., 2011), to increase dishonesty (Shalvi and De Dreu, 2014; Aydogan et al., 2017), and to amplify negative social emotions like envy and schadenfreude evoked by unfair money allocations (Shamay-Tsoory et al., 2009). Additionally, inhaled OT increases sensitivity to the social information of co-players in a social dilemma game (Declerck et al., 2010, 2013; Mikolajczak et al., 2010; Bartz et al., 2011;), indicating a more complex role of the neuropeptide in cooperative behavior (Bartz et al., 2011) than has often previously been assumed. This more differentiated view is also supported by animal studies showing that endogenous OT release in the rodent brain correlates with aggression in mate-guarding behavior (Bales and Carter, 2003) and with maternal aggression in defending offspring against intruders (Bosch, 2005; Bosch and Neumann, 2012).

In this work, we examine the effect of OT on the enforcement of cooperation, since it has been shown that the inclination to altruistically punish uncooperative behavior with no egoistic material benefits is a crucial factor for the sustainability of cooperation (Fehr and Schmidt, 1999; Fehr and Gächter, 2002; Fehr and Fischbacher, 2004). In building upon studies suggesting that OT is associated with social emotions like envy and schadenfreude in unfair money allocations (Shamay-Tsoory et al., 2009), it is straightforward to assume that inhaled OT may amplify negative emotions (e.g. 'anger') toward defectors and therefore increase the inclination to enforce the norm of cooperation.

Our primary hypothesis concerns punishment inclination in a social dilemma game. We therefore hypothesize that inhaled OT increases the inclination to punish defectors relative to a placebo in a social dilemma game. To confirm previous findings on the motivational factors of altruistic punishment (Hopfensitz and Reuben, 2009), we also asked participants to indicate the emotions they experienced before and after the social dilemma game. As our supporting hypothesis, we predicted an amplification of negative emotions directed toward defectors following the violation of a social norm.

Finally, to explore OT's effects on the efficiency of a punishment institution, we also conducted further analyses examining the directionality and the effectiveness of punishment—important features that may determine the sustainability of the social norm.

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