Title: The Neuroscience Behind Superhuman Acts of Generosity

Twenty-three years ago, Harold Mintz underwent surgery at Georgetown University Hospital to give one of his kidneys to a stranger. 

He became one of the first anonymous living organ donors in the country, and his brain was later studied by Georgetown Professor Abigail Marsh and other researchers to see if he and other such donors had different brain structures than people who hadn’t donated an organ. 

Mintz’s brain was different: His right amygdala, the region of the brain that processes emotions, was bigger. But researchers didn’t know why — or what the motivation was behind his extreme altruism — until now. 

In a new paper published in PNAS Nexus, an interdisciplinary team of Georgetown scientists sheds new insight into why extreme altruists help strangers for no apparent benefit to themselves. Their study is the first to measure extreme altruists’ brain activity as they make generous decisions in real-time.

Social Discounting and the Generosity Gap

Most people are more generous toward their family and friends than they are toward strangers, a behavior called social discounting. Because social discounting is so ubiquitous, the question of why certain people choose to be altruistic toward strangers has long puzzled researchers.

“People who have previously engaged in extraordinary acts of altruism, such as non-directed kidney donors, incur significant risks and costs in order to benefit strangers just as they would for close others,” said Shawn Rhoads (G’22), the paper’s lead author and a postdoctoral research fellow at the Icahn School of Medicine at Mount Sinai in New York City. “In our study, we scanned the brains of altruists to understand the neural processes underlying these kinds of decisions.”

The team conducted MRI scans of anonymous kidney donors as they made generous or selfish decisions and compared those to a control sample of ordinary people. They learned that the motivation behind extreme altruists’ acts of generosity was a truly benevolent one: they sincerely care. 

“Everything we have learned about extraordinary altruists up until now has suggested to us that they help strangers because they genuinely care about them more,” said co-author Marsh, a professor in the Department of Psychology. “This study supports that conclusion more definitively and helps us understand the brain mechanisms that allow altruists to value and care more about others.”

Marsh, who is internationally recognized for her research into what she calls the ‘caring continuum,’ which encompasses both psychopathy and extreme altruism, mentored Rhoads while he pursued his Ph.D. on the Hilltop. Their research has recently been featured on 60 Minutes and in the new documentary, Confessions of a Good Samaritan, and was supported by a grant from the National Science Foundation. 

Rhoads and Marsh led an interdisciplinary, cross-campus research team through a collaboration between the Department of Psychology in the College of Arts & Sciences, the Interdisciplinary Program in Neuroscience in Biomedical Graduate Education, and the Department of Psychiatry and the Department of Neurology in Georgetown University Medical Center.

Marsh said their research sheds light on the very human impulses of extreme altruists. 

“This research is important because it contradicts the idea that caring about and helping strangers is somehow superhuman,” said Marsh. “Real-world altruists get called ‘saints’ and ‘guardian angels’ a lot, as though a real human being would not be capable of an act of such incredible generosity. But we can now explain this kind of altruism through what we know about the neuroscience of generosity.”

The Neuroscience of Generosity

Previous studies from other researchers suggested that people make generous decisions to help strangers because they are suppressing the urge to be selfish. However, this new study suggests that extreme altruists help strangers because they have different neural processes in regions of the brain responsible for calculating the value of others’ welfare. In other words, they genuinely care more about their welfare.

“We found divergent neural activation reflecting the subjective value placed on others’ welfare between altruists and controls. Several of these regions, including the anterior cingulate and amygdala, are known to support prosocial decisions. In other words, activation in these regions encodes the value of acting generously,” said Rhoads. “Altruists may sacrifice more for distant strangers due to their more unbiased value-related neural responses across both close and distant others.”

The researchers also explored whether it was possible to make people who aren’t extreme altruists more generous or cause their brain activity patterns to become similar. After testing an online loving-kindness meditation training intervention, they found they could not induce generosity, though there could be future opportunities to mine deeper into this intervention.  

“Although our attempt to make typical adults behave more like real-world altruists didn’t pan out, the results of our neuroimaging study will give us information to develop better interventions in the future,” said Marsh. 

Decades of Doing Good

Mintz, who donated his kidney to a stranger in 2000, had been driven to the operating table by a series of life events: the loss of his own father at an early age; chance meetings with strangers who needed organ transplants that stuck in his head; a movie he watched on a cross-country flight about a grandson donating his kidney that included a number to call for more information in the credits. 

Mintz called the number and remembered asking: “If I don’t give my kidney this week, will someone die waiting for it?” They would, he learned. 

The recipient of his kidney was Gennet Belay, an immigrant whose family escaped political persecution in Ethiopia. She had just days to live when she was matched with Mintz. 

Years later, Belay is alive and well and the two are close friends, a friendship that was chronicled in a 2016 short documentary. 

“You couldn’t find two more different people if you tried,” said Mintz, who met Belay three months after the surgery. “And yet today I’m as close with her family as with mine – we are family.”

Mintz’s impulse for good has given Belay decades of life with her family.

“When somebody talks about what I did, it’s often called ‘selfless.’ Selfless to me is doing something where you get no benefit. That’s not me. I got tons from what I did. I continue to get tons from it,” Mintz said in the documentary. “But [it’s] not – ‘I’m a hero, I’m that great.’ No, I’m normal. And I think normal people can do outstanding things.”