"When we make decisions, a network of brain regions calculates how valuable our options are," explains lead author Dr Molly Crockett, from the University of Oxford. "Ill-gotten gains evoke weaker responses in this network, which may explain why most people would rather not profit from harming others. Our results suggest the money just isn’t as appealing."
The team, who did the research at the UCL Wellcome Centre for Neuroimaging, scanned volunteers’ brains as they decided whether to anonymously inflict pain on themselves or strangers in exchange for money.
Twenty-eight pairs of participants were randomly assigned to be either the ‘decider’ or the ‘receiver’ of an electric shock.
The researchers found:
as participants decided between more profitable options or those with fewer shocks, a brain network that includes the striatum signalled how beneficial each option was
the network responded less to money gained from giving a shock to others than to money gained from shocking oneself – but only in those people who behaved morally
the lateral prefrontal cortex (LPFC), a brain region involved in making moral judgments, was most active in trials where inflicting pain yielded minimal profit.
In a follow-up study, participants made moral judgements about fictional decisions to harm others for profit, and considered similar trials where people inflicted pain for just a small amount of money to be the most blameworthy.
Taken together, the findings suggest the LPFC was assessing blame. When people refused to profit from harming others, this brain region was communicating with the striatum, suggesting that neural representations of moral rules might disrupt the attraction of ill-gotten gains encoded in the striatum.
"Our findings suggest the brain internalises the moral judgments of others, simulating how much others might blame us for potential wrongdoing, even when we know our actions are anonymous," says Dr Crockett.