How could someone do that to another human being?

It’s a question that surfaces whenever we encounter acts that defy empathy: an immigration officer separating a child from their parents, a soldier shooting an unarmed civilian in the name of genocide, a prison guard forcing an inmate to eat dog food naked, a driver speeding through a group of protesters with different political beliefs.

These acts jar us because they run counter to how we think of ourselves as human beings. Most of us assume a baseline capacity for empathy, fairness, and care. When we witness cruelty, it violates that assumption, leaving us struggling to understand what Nancy Pineda-Madrid, the T. Marie Chilton Chair of Catholic Theology, describes as a “soul sickness.” Pineda-Madrid teaches theology in the LMU Bellarmine College of Liberal Arts and wrote about the brutality of feminicide in her book “Suffering and Salvation in Ciudad Juárez.”

“Those who commit [these] acts create a situation in which they live in acute conflict with the essence of who they are as human beings,” says Pineda-Madrid.

So why do people do it? How do they depart from their very essence and hurt others?

To understand cruelty, psychologists say we need to look at how people make it possible for themselves to inflict pain without registering the act or victim. “You need to find a way to justify what you did,” says Máire Ford, associate vice provost for Faculty Development and professor of social psychology in the LMU Bellarmine College of Liberal Arts. People who commit acts that seem to lack empathy still need to protect their self-image.“If you feel like you did something terrible to someone, that’s going to cause a drop in your self-esteem,” says Ford. “By justifying it, that boosts your sense of, ‘No, I’m still a good person.’”

Albert Bandura, a psychologist best known for his work on social learning and human behavior, studied this phenomenon and called it moral disengagement. He described ways people can mentally “switch off” their own moral rules, allowing them to do harm without feeling guilt. These strategies include moral justification — framing harmful acts as serving a greater good; displacement of responsibility — blaming authority or circumstance; and, most importantly, dehumanization.

“Dehumanization is the psychological process of denying somebody their full humanness,” Ford explains. When people are seen as less than human — stripped of thoughts, feelings, or moral worth — it becomes easier to hurt them. In other words, before someone can commit cruelty without feeling guilty, they first convince themselves that their victim is not fully human. This is what makes moral disengagement possible.

Early research examined what this looks like through extreme atrocities in order to make sense of them — like the Nazi’s extermination of Jewish people through the Holocaust, or the Rwandan genocide. Nazi propaganda, for example, frequently depicted Jewish people as vermin and pests. By showing them as less than human, ordinary people could participate in — or turn a blind eye to — horrific acts without feeling the full weight of guilt. Australian social psychologist Nick Haslam, building on Bandura’s work, would go on to call this “animalistic dehumanization,” where people are denied traits that separate humans from animals. He also expanded mechanistic dehumanization, where people are denied traits that make them warm, emotional, and individual — treating them like objects or machines — such as when perpetrators in war may describe victims as “target,” “cargo,” or “collateral damage.”

Because those who succumb to the process of dehumanizing others become, as Pineda-Madrid alluded, in conflict with what it means to be human, they face an ironic outcome. They become dehumanized themselves. Ford notes that one of the tragic costs of dehumanization is that those who are victims of it, may come to incorporate how they are treated into their sense of self. Those who perpetrate cruel acts trigger a similar process: Because they treat others as less than human, they, too, are seen as less than human. They become history and society’s “monsters” and “villains.”

Over time, however, the focus of dehumanization research has expanded to subtler forms: treating others as “less than” rather than fully non-human. Today, that shift feels especially relevant. We may not use the language of rats or machines, but the same psychological process plays out in everyday life. It happens when we dismiss someone’s suffering because they hold different political beliefs, when online arguments turn strangers into faceless avatars, or when public rhetoric paints groups of people as “lazy,” “dangerous,” or “undeserving.” These are quieter acts of dehumanization — small, repeated erosions of empathy that, left unchecked, can escalate into the kind of cruelty that history has shown us all too well.

It can appear in workplaces, personal relationships, political conflicts, or online disputes. “Someone may view you as not worthy of respect because you’re, for example, not seen as smart enough. That takes away pieces of human cognition or human emotion,” says Ford. For example, social media often amplifies dehumanizing rhetoric: Commenters reduce public figures, activists, or even neighbors to caricatures, stripping away nuance and individual humanity.

Research also links dehumanization to social identity theory, which suggests people naturally categorize themselves and others into “in-groups” and “out-groups,” deriving self-esteem from the status of their group. This categorization is largely automatic. “We can’t help but categorize people,” says Adam Fingerhut, psychology professor in the LMU Bellarmine College of Liberal Arts. “Part of our self-esteem is tied to the groups that we belong to,” he explains. Evolutionary pressures may have reinforced these mechanisms: Out-group members could represent competition or threats, prompting prioritization of survival over morality.

The path to dehumanization comes about, in part, as we see in political and ideological divides across the world right now, in how the out-group can become positioned.

“One way we make sure we’re part of the good groups is by discriminating against the out-group,” says Fingerhut. “By kicking them down, we elevate our group, and in turn, ourselves.”

When that escalates, and an out-group is framed as immoral, threatening, or less than human, it becomes easier to justify acts that would normally clash with moral instincts. “When you think your group has moral superiority over the other group, then not only is it important to favor your in-group, it’s important that you get rid of the out-group, because they’re immoral,” Fingerhut adds.

For Pineda-Madrid, beauty, reflection, and human encounter play crucial roles in restoring empathy: “Beauty often can take a hardened heart and soften it,” she says. “I think if we can reflect on our own experience, that can soften the innards of us, individually or collectively, and move us beyond the soul sickness.”

As Pineda-Madrid frames it, the work of rehumanization is not merely about ethics; it is about being true to who we are meant to be. Dehumanizing is a deviation from our essential human orientation, a sickness of the soul. To reconnect with the humanity of another is to reconnect with our own, to reweave the fabric of empathy and moral awareness that allows us to live fully human lives.

In the end, understanding why people dehumanize — and how they can be rehumanized — offers both caution and hope. It shows the fragility of moral attention and the power of human connection. And it reminds us that the question is not only how someone could do that to another human being, but how we can foster conditions in which such acts become harder to imagine, let alone commit.

Alexander Huls is a writer based in Toronto. His work has appeared in The New York Times, The Atlantic, Esquire, Popular Mechanics, and elsewhere. His “The Loud-Mouthed Neighbors,” a feature story about crows, appeared in the winter 2023 (Vol. 11, No. 2) issue of LMU Magazine. Follow him @alxhuls.