Individuals learn by comparing the outcome of chosen and unchosen actions. A negative counterfactual value signal is generated when this comparison is unfavorable. This can happen in private as well as in social settings—where the foregone outcome results from the choice of another person. We hypothesized that, despite sharing similar features such as supporting learning, these two counterfactual signals might implicate distinct brain networks. We conducted a neuropsychological study on the role of private and social counterfactual value signals in risky decision-making. Patients with lesions in the ventromedial prefrontal cortex (vmPFC), lesion controls, and healthy controls repeatedly chose between lotteries. In private trials, participants could observe the out-out-comes of their choices and the outcomes of the unselected lotteries. In social trials, participants could also see the other player’s choices and outcome. At the time of outcome, vmPFC patients were insensitive to private counterfactual value signals, whereas their responses to social comparison were similar to those of control participants.Atthetimeofchoice, intact vmPFC was necessary to integrate counterfactual signals in decisions, although amelioration was observed during the course of the task, possibly driven by social trials. We conclude that if the vmPFC is critical in processing private counterfactual signals and in integrating those signals in decision-making, then distinct brain areas might support the processing comes of social counterfactual signals.
Bibliographical noteFunding Information:
The authors would like to thank all patients with brain lesion for their participation in the study. We also thank Gabriele Chierchia for his crucial help with recruitment and testing of the Italian control participants, as well as Ben Timberlake for editing the manuscript. The study was funded by the European Research Council (ERC Consolidator Grant 617629) and the Agence National de la Recherche (ANR-11-EMCO-010) grants to G. C. and N. B.