Is the dorsolateral prefrontal cortex causally implicated in prosocial behaviour? A meta-analytic reassessment of brain stimulation evidence

Human social life depends on the ability to balance self-interest with prosocial motives. The right dorsolateral prefrontal cortex (rDLPFC) has been proposed to play a causal role in this regulation, yet empirical evidence is mixed. We conducted a meta-analysis of experimental studies using non-invasive brain stimulation to test how exciting versus inhibiting the rDLPFC affects behaviour in economically incentivized social tasks (33 papers, 37 studies, 81 effect sizes). Across different domains of prosocial behaviour, excitatory stimulation of the rDLPFC was associated with reduced self-interest, whereas inhibitory stimulation increased selfishness. Moderator analyses revealed substantial heterogeneity across prosocial behaviour domains, with the strongest effects of rDLPFC stimulation observed for positive and negative reciprocity. Critically, a robust Bayesian model-averaged meta-analysis provided strong evidence for publication bias. After accounting for publication bias, the model-averaged effect favoured the null hypothesis over a non-zero effect by approximately a factor of four. Similar attenuation toward zero was observed when analyses were stratified by stimulation type (excitatory vs. inhibitory), technique (TMS vs. tDCS) and when restricted to positive and negative reciprocity, with bias-adjusted estimates in all cases not credibly different from zero. Overall, these findings cast doubt on the robustness of claims that the rDLPFC plays a causal role in promoting prosocial behaviour and call attention to the importance of well-powered replication studies as well as strategies that reduce biases towards publishing null results in social neuroscience and neuroeconomics.