It is a mystery that has perplexed psychologists and philosophers since the dawn of humanity: why are most people honest?
Now, using a complex array of MRI machines and electrocution devices, scientists claim to have found the answer.
Researchers at University College London discovered that at a physical level the brain finds decency far more satisfying than deception.
The trial revealed that, despite accumulating a large amount of money, most participants derived no deep-seated satisfaction if the success was gained at the expense of others.
Ill-gotten gains evoke weaker responses, which may explain why most people would rather not profit from harming others
Dr Molly Crockett
Published in the journal Nature Neuroscience, the study indicates that, at least at a psychological level, the old adage that “crime doesn’t pay” is right.
“When we make decisions, a network of brain regions calculates how valuable our options are,” said Dr Molly Crockett, who led the research.
“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 research team scanned volunteers’ brains as they decided whether to anonymously inflict pain on themselves or strangers in exchange for money.
The experiment involved 28 couples of participants who were paired off and given the ability to give each other small electric shocks.
They were given the option of selecting sums of money that were related to a shock either for themselves of their partner.
The researchers noticed that, as they made their decisions, a region of the brain called the striatum, key to the understanding of value, was activated.
MRI imaging found that this brain network was far more active when the participants gained money while inflicting pain on themselves than on another, suggesting they found it instinctively more valuable.
“Our findings suggest the brain internalizes the moral judgments of others, simulating how much others might blame us for potential wrongdoing, even when we know our actions are anonymous,” said Dr Crockett.
The scans also revealed that an area of the brain involved in making moral judgments, the lateral prefrontal cortex, was most active in trials where inflicting pain yielded minimal profit.
In an allied study, participants were asked to make moral judgements about decisions to harm others for profit.
It showed that when people refused to profit from harming others, this region was communicating with the striatum.
The researchers believe this shows that normal societal moral rules are visible in the form of neurological signaling, and that these disrupt the value we might otherwise place on ill-gotten gains.
They insisted that the electric shocks administered to participants were carefully matched to each recipient’s pain threshold to be “mildly but tolerably painful”.
Senior author Professor Ray Dolan, from the UCL Max Planck Centre for Computational Psychiatry and Ageing Research at UCL,said: "What we have shown here is how values that guide our decisions respond flexibly to moral consequences.
“An important goal for future research is understanding when and how this circuitry is disturbed in contexts such as antisocial behaviour."
Previous research by UCL has suggested that generosity and alturism are governed by a specific region of the brain - the subgenual anterior cingulate cortex - and that it works naturally better in some people than in others.
MRI scans found the cortext was the only part of the brain to light up when the subject thought about helping others.