Forgiveness and cognitive control - Provoking revenge via theta-burst-stimulation of the DLPFC

In order to act in a socially acceptable way, the ability to forgive is indispensable. It has been suggested that forgiveness relies on cognitive control, more specifically inhibition. In this study, we combined an ultimatum game (UG) and a dictator game (DG) with inhibitory, continuous theta-burst stimulation (cTBS; verum vs. placebo, within-subjects design) of the right dorsolateral prefrontal cortex (DLPFC) to investigate the effect of reduced cognitive control on forgiveness. To this end, participants played an UG against fair and unfair opponents, where they had to accept or reject (fair and unfair) monetary offers, and then received a cTBS prior to playing a DG against the same opponents with reversed roles. The participants now had the possibility to forgive the unfair opponents (allocation of a fair amount of money) or to take revenge whereby the cTBS effects were assessed with functional near-infrared spectroscopy. Following verum cTBS, participants allocated significantly less money to their unfair opponents than in the placebo cTBS condition. Also, reaction times (RTs) differed significantly between verum and placebo cTBS for unfair opponents (higher RTs following verum stimulation) but not for fair opponents. These results strongly indicate that cognitive control is a fundamental requirement for overcoming unwanted emotional responses.