Experiment involving theoretical financial reward in exchange for uncomfortable electric shocks on self or others reveals brain preference for less pain and lower profit

It’s the age-old question: does money buy happiness? The answer, according to scientists, depends on how you make your fortune.

A new study has found that ill-gotten gains elicit a weaker response in the brain’s reward system than money that has been earned scrupulously. The findings could explain why most of us are reluctant to exploit others for financial gains.

Molly Crockett, who led the work at University College London, said: “Our results suggest the money just isn’t as appealing.”

However, the experiment also revealed a handful of outliers – perhaps mirroring the spectrum of moral integrity seen across society – who found it equally, if not more, gratifying to profit at the expense of an anonymous partner.

The study distilled the complex issue into a single tractable question: would you rather be paid to receive electric shocks yourself or would you prefer someone else to take the pain for you – and if so, by how much?

The experiment, described in the journal Nature Neuroscience, involved 56 pairs of participants who were randomly assigned the role of either “decider” or “receiver”.

The decider’s job was to chose between two options, each giving a number of electric shocks and a price tag. For instance, 10 shocks for £10, or 20 for £11?

Half of the time, decisions related to shocks that would be inflicted on the decider, and half for the receiver – but the decider would always get the money. Just one of the decider’s choices would be selected at random and enacted at the end of the study and the pain was designed to be uncomfortable, not excruciating.

“We can measure how much money is required to shock the other person and how much they require to shock themselves and take the difference between those two quantities,” said Crockett.

On average, people required an extra 17p per shock to punish their anonymous partner, but one third of the participants bucked the altruistic trend and were more eager to spare themselves.

The deciders weighed up the options while lying inside an MRI scanner, which revealed a brain network including the striatum, a structure deep inside the brain, which is known to be key to value computation.

The brain scans revealed the internal values each person assigned to avoiding shocks and sparing their partner and this activity closely matched the choices made in the experiment.

A second brain region, called the lateral prefrontal cortex, appeared to be factoring guilt into decision-making by downgrading the value of a reward when it conflicted with moral feelings about hurting others for profit. This area was most active in trials that involved inflicting pain for a small profit.

“It seemed that the worst kind of choice you can make is inflicting a lot of pain for a tiny amount of money,” said Crockett, who is now based at the University of Oxford. “Twenty shocks for 10p seems worse somehow than delivering the same for £20.”

The researchers are now hoping to study moral decision making in contexts that are closer to real life. The latest study, Crockett said, involved a “fairly black or white situation”.

“In our daily lives there’s a lot more grey area on the benefits to ourselves versus the costs to another person,” she added. “It’s within this grey area that a lot of moral failure happens. We want to find where those boundaries are.”