Why, in a given society, do some people follow destructive orders, even participating in genocide, while others risk their lives to resist and save others?

A new neuroscientific study of individuals who lived through the 1994 Genocide against the Tutsi in Rwanda and published in American Psychologist today, offers the first direct evidence that the brains of those who rescued others process others’ distress differently from those who participated in the violence or those who remained bystanders.

Researchers compared three groups of Rwandans who had taken profoundly different paths during the genocide: former perpetrators, bystanders, and rescuers, individuals who defied orders to save lives. On a daily basis, they travelled across rural Rwanda with a portable electroencephalogram and their computers. “This is the first study to use neuroscience methods to investigate what distinguishes these groups. On a human level, it was an intense experience. Beyond hearing their stories, it required a long process of building trust before participants felt comfortable wearing these devices on their heads”, said Prof. dr. Emilie Caspar, principal investigator of the study.

Using an EEG-based task adapted from classic obedience paradigms, participants were instructed by an experimenter to take or not take money from another person, allowing researchers to measure obedience, disobedience, and the neural processes that accompany these decisions.

The neuroscience of moral resistance
The study found that rescuers showed stronger neural responses to others’ sadness when money was taken from them, a marker of emotional empathy known as the Late Positive Potential (LPP), compared to bystanders and former perpetrators. This enhanced emotional processing was also linked to higher rates of prosocial disobedience, when participants refused to obey immoral orders to take money from the other person.

“At the neural level, rescuers appear to feel others’ suffering more intensely,” says Prof. dr. Emilie Caspar. “That heightened emotional engagement may help explain why they chose to help those targeted by the genocidal process, rather than participate or turn a blind eye.”

In contrast, former perpetrators were more likely to obey harmful commands and showed lower feelings of responsibility, consistent with self-reported tendencies to minimize their role in past actions. Yet, across all groups, more than half of participants disobeyed immoral orders, an unexpectedly high rate compared to previous studies conducted among younger generations born after the genocide, where the disobedience rate was close to null.

“This suggests that obedience is not a fixed trait,” Prof. dr. Caspar explains. “Life experience, especially living through genocide, may profoundly change how people weigh authority against moral responsibility. But simply knowing about these events, for instance among the new generations, appear not being sufficient to resist harmful influence.”

Rescuers also differed in how they made decisions. Their decision-making times suggested deeper reflection before acting, and they mentioned a wider range of motivations for disobedience, including empathy, family upbringing, and Rwanda’s history. Many rescuers, more than former perpetrators or bystanders, also reported having role models who had engaged in rescue actions during their childhood. These early influences may have helped shape their later choices to resist authority and protect others.

The Banality of Evil
The study also found no stable neural differences between former perpetrators and bystanders, challenging the notion that participation in genocide stems from a fixed “violent personality.” Instead, the findings underscore that situational and social factors, such as propaganda, dehumanization, and fear, are central drivers of mass violence.

“This finding is crucial,” explains Prof. Dr. Caspar. “In everyday thinking, people tend to attribute genocidal actions to dark personality traits or to some dysfunction of the brain. From an emotional point of view, this is understandable. But finding no difference at all supports Hannah Arendt’s idea of the ‘banality of evil’: participation in genocide is not about who you are, but about the ordinary social pressures and circumstances that can lead people to commit extraordinary harm.”

Beyond Milgram: Real-world obedience and its implications
For decades, researchers have relied on Stanley Milgram’s famous experiments to understand why ordinary people commit atrocities under orders. However, Milgram’s studies never included individuals who had lived through a genocide, nor did they identify the neural mechanisms underlying why some people resist while others display destructive obedience.

This new work bridges that gap, testing whether theories of obedience developed in laboratories hold true among those who have directly experienced mass violence.

“Despite the promise of ‘Never Again,’ such atrocities continue to occur,” says Prof. Dr. Emilie Caspar. “Understanding how ordinary people find the strength to resist immoral orders is not only a scientific question—it is a societal one. If we can identify the mechanisms that support moral courage, perhaps we can help foster them.”

The researchers hope that their work will inspire educational and peacebuilding initiatives that cultivate empathy, critical thinking, and resistance to destructive authority.