“An Eye for an Eye”? Neural Correlates of Retribution and Forgiveness
Figure 1
Design and schematic structure of the fMRI paradigm (The subject of the photograph has given written informed consent, as outlined in the PLOS consent form, to publication of his photograph).
a. Ultimatum game: Subjects played against six different opponents (two male human players, two female human players and two computer players), who offered an amount of money varying between zero € and five €. Nevertheless, subjects had the possibility to accept or to reject the offered amount of money by pressing a button. Finally, the subjects were informed by a visual feedback about the accepted or rejected amount of money.
b. Dictator game: In the second run of the experiment, subjects played against the previously introduced six opponents. In contrast to the ultimatum game presented in the first run, subjects had now the possibility to share the money according to their needs and beliefs. For this reason, our subjects were in the position to punish or to reward previously unfair or fair opponents. Finally, subjects were informed by a visual feedback about their gain in this trial and the amount of money assigned to the opponent.
All trials were separated by a 4.0-5.0s intertrial interval (ITI). In addition, eight separate baseline events varying between 4.0 and 5.5 seconds were presented per run.