title: Dopaminergic stimulation increases selfish behavior in the absence of punishment threat.
abstract: BACKGROUND
  People often face decisions that pit self-interested behavior aimed at maximizing personal reward against normative behavior such as acting cooperatively, which benefits others. The threat of social sanctions for defying the fairness norm prevents people from behaving overly selfish. Thus, normative behavior is influenced by both seeking rewards and avoiding punishment. However, the neurochemical processes mediating the impact of these influences remain unknown. Several lines of evidence link the dopaminergic system to reward and punishment processing, respectively, but this evidence stems from studies in non-social contexts.
  
  
  OBJECTIVE
  The present study investigates dopaminergic drug effects on individuals' reward seeking and punishment avoidance in social interaction.
  
  
  METHODS
  Two-hundred one healthy male participants were randomly assigned to receive 300 mg of L-3,4-dihydroxyphenylalanine (L-DOPA) or a placebo before playing an economic bargaining game. This game involved two conditions, one in which unfair behavior could be punished and one in which unfair behavior could not be punished.
  
  
  RESULTS
  In the absence of punishment threats, L-DOPA administration led to more selfish behavior, likely mediated through an increase in reward seeking. In contrast, L-DOPA administration had no significant effect on behavior when faced with punishment threats.
  
  
  CONCLUSIONS
  The results of this study broaden the role of the dopaminergic system in reward seeking to human social interactions. We could show that even a single dose of a dopaminergic drug may bring selfish behavior to the fore, which in turn may shed new light on potential causal relationships between the dopaminergic system and norm abiding behaviors in certain clinical subpopulations.
authors.affiliation: Institute of Psychology, Social and Affective Neuroscience, University of Basel, Basel, Switzerland, andreas.pedroni@unibas.ch.
authors.forename: Andreas
authors.initials: A
authors.lastname: Pedroni
authors.forename: Christoph
authors.initials: C
authors.lastname: Eisenegger
authors.forename: Matthias N
authors.initials: MN
authors.lastname: Hartmann
authors.forename: Urs
authors.initials: U
authors.lastname: Fischbacher
authors.forename: Daria
authors.initials: D
authors.lastname: Knoch
mesh_terms: D001519:Behavior / Q000187:drug effects*; D003627:Data Interpretation, Statistical; D003657:Decision Making; D015259:Dopamine Agents / Q000009:adverse effects / Q000494:pharmacology*; D004311:Double-Blind Method; D004532:Ego; D006801:Humans; D007980:Levodopa / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D011678:Punishment / Q000523:psychology*; D012201:Reward; D012931:Social Environment; D055815:Young Adult
chemical_list: D015259:Dopamine Agents; D007980:Levodopa
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