Moral inconsistency is based on the vmPFC's insufficient representation across tasks and connectedness

Moral inconsistency-misaligning one's behavior with the same moral principle of judging others-undermines personal reputations and social relationships. This study explores the neural underpinnings of moral inconsistency in a profit-honesty trade-off setting with functional magnetic resonance imaging and transcranial temporal interference stimulation (tTIS). Experiment 1 demonstrated that participants showed inconsistent sensitivity to profit and honesty between moral behavior and moral judgment tasks. Furthermore, multivariate pattern analyses showed that participants with higher moral inconsistency exhibited reduced judge score representation across tasks and weaker connectedness during the moral behavior task in the ventromedial prefrontal cortex (vmPFC). Experiment 2 showed that tTIS modulation of the vmPFC increased moral inconsistency. These findings indicate the vmPFC's involvement in the neural basis of moral inconsistency. While individuals with higher moral inconsistency may be aware of moral principles when making decisions, they consider moral principles less and do not integrate them into their own behaviors.