People hurt others for a wide range of reasons, from momentary losses of self-control to calculated strategies for personal gain. There is no single explanation, but decades of psychology, neuroscience, and sociology research have mapped out the major forces at work. Understanding these forces won’t excuse harmful behavior, but it can make sense of something that often feels senseless.
Two Fundamentally Different Kinds of Aggression
Not all harm comes from the same place. Researchers distinguish between two types based on what’s driving the person in the moment.
Reactive aggression is the hot, impulsive kind. Someone feels provoked, threatened, or emotionally overwhelmed, and they lash out. It’s characterized by emotional instability and poor impulse control. A person who punches a wall after an argument or snaps at a loved one during stress is acting reactively. The aggression isn’t planned; it erupts.
Proactive aggression is cold and strategic. The person hurts others to get something they want: power, status, money, control. They aren’t emotionally flooded. In fact, proactive aggression is associated with low emotionality and high instrumentality. A bully who targets a classmate to climb a social hierarchy, or a coworker who sabotages a colleague to get a promotion, is using harm as a tool.
These two types have different biological signatures. Genetic variants that reduce serotonin activity are linked to reactive aggression, while variants associated with higher functioning in those same systems correlate with the proactive type. In other words, the brain chemistry behind a hot-tempered outburst is genuinely different from the chemistry behind a calculated betrayal.
What Happens in the Brain
Your brain has a built-in conflict between two systems. One is the threat-detection center (deep in the brain’s emotional core), which fires up when you perceive danger, disrespect, or frustration. The other is the rational, planning area behind your forehead, which acts as a brake, helping you pause, consider consequences, and choose a measured response.
In people prone to impulsive aggression, the brake doesn’t work well. Research published in the Proceedings of the National Academy of Sciences found that impulsive aggression is linked to a dysfunction in the inhibitory connections running from that rational braking system down to the emotional threat center. When those connections are weak or disrupted, the emotional alarm fires and there’s nothing to stop the person from acting on it immediately. This isn’t a choice in the way most people think of choices. It’s a failure of a neural circuit that, in others, would have caught the impulse before it became action.
This doesn’t mean biology is destiny. It means some people enter situations with a neurological disadvantage when it comes to managing anger, and without learning compensatory skills, they’re more likely to cause harm.
Personality Traits That Predict Harm
Some people hurt others not because they lose control, but because of enduring patterns in how they relate to the world. Three personality traits, sometimes studied together as the “dark triad,” each predict interpersonal harm in distinct ways.
People high in Machiavellianism tend to manipulate and deceive others for personal gain. They view relationships transactionally and may see hurting someone as simply the most efficient path to their goal. People high in psychopathic traits show a cold, impulsive nature in relationships and can take pleasure in causing pain. The coldheartedness and antisocial impulsivity associated with psychopathy are especially strong triggers for relational aggression, things like spreading rumors, social exclusion, and reputation destruction. Narcissistic individuals, meanwhile, carry an inflated sense of superiority and entitlement. They’re particularly reactive to negative social feedback. When their self-image is threatened, they often resort to aggression to restore their standing.
All three traits predict relational aggression, but psychopathy tends to be the strongest predictor. What unites them is a willingness to treat other people as obstacles or instruments rather than as full human beings deserving of care.
When People Can’t Read Their Own Emotions
Sometimes harm stems from a surprising deficit: not understanding what you’re feeling. A condition called alexithymia describes people who struggle to identify, differentiate, and label their own emotions. They experience physical sensations (racing heart, tight chest, clenched jaw) but can’t connect those sensations to a feeling like anger, fear, or sadness.
This matters because recognizing what you feel is the first step toward managing it. If you can’t name your anger, you can’t decide what to do with it. Research shows that people with high alexithymia report significantly more anger after interacting with people from different social groups, and they rate themselves as more aggressive people. Interestingly, in controlled settings they don’t always act more aggressively than others, but in real life, where situations are messier and stakes are higher, the inability to process emotions adaptively creates a persistent risk of harm. The aggression that comes from emotional blindness is often confusing to both the person doing it and the person on the receiving end.
How People Justify Hurting Others
One of the most important findings in this field is that most people who cause harm don’t think of themselves as bad people. They use a set of mental strategies, described by psychologist Albert Bandura as moral disengagement, to disconnect their actions from their conscience. There are eight of these strategies, and most of us have used at least one.
- Moral justification: reframing the harm as serving a higher purpose (“They deserved it” or “I did it to protect my family”).
- Palliative comparison: comparing the harm to something worse (“At least I didn’t hit them”).
- Euphemistic labeling: using softer language to disguise what happened (“I was just being honest” instead of “I humiliated them”).
- Displacing responsibility: blaming an authority or external force (“My boss made me do it”).
- Diffusing responsibility: sharing blame across a group so no one feels personally accountable (“Everyone was doing it”).
- Minimizing consequences: downplaying the damage (“It wasn’t that bad” or “They’ll get over it”).
- Dehumanization: viewing the victim as less than fully human, which removes the normal emotional barrier against cruelty.
- Blaming the victim: attributing the harm to something the victim did (“They brought it on themselves”).
These strategies operate mostly below conscious awareness. People don’t sit down and decide to morally disengage. The rationalizations arise automatically, protecting self-image while enabling behavior that would otherwise trigger guilt.
Dehumanization at Scale
Dehumanization deserves special attention because it explains not just individual cruelty but collective violence. When one group begins to see another as less than fully human, the normal revulsion against causing harm weakens dramatically.
This process takes two main forms. Animalistic dehumanization strips people of qualities considered uniquely human, like reason, civility, and moral sensitivity, essentially casting them as animals. Mechanistic dehumanization strips people of warmth, emotion, and individuality, treating them as objects or machines. Both forms make it psychologically easier to inflict suffering.
According to the Genocide Watch model, dehumanization is the mechanism that prepares perpetrators to overcome their natural revulsion against killing. It’s a consistent precursor to mass violence throughout history. But it also operates in everyday life at smaller scales: when someone dismisses a homeless person as subhuman, when online discourse reduces opponents to caricatures, when workplace culture treats employees as interchangeable parts. Each instance lowers the psychological cost of causing harm.
Can People Who Hurt Others Change?
Yes, and there’s solid evidence for it. Cognitive behavioral therapy focused on anger management has been studied extensively across populations, including people with histories of violence. A meta-analysis found that completing a CBT-based anger management program reduced the risk of general reoffending by 42% and violent reoffending by 56%. Even among those who didn’t complete the full program, exposure to CBT reduced general recidivism by 23% and violent recidivism by 28%.
These programs work by targeting the specific mechanisms described above. They teach people to recognize their emotional states before they escalate, to identify the distorted thinking patterns that justify harm, and to practice alternative responses until those responses become more automatic than the aggressive ones. The neural brake that’s weak in impulsively aggressive people can, to a meaningful degree, be strengthened through practice.
Change is harder for people whose aggression is proactive and tied to deep personality patterns. But even here, therapeutic approaches that build empathy and challenge the instrumental view of relationships show promise. The capacity to stop hurting others isn’t fixed at birth. It’s a skill, and like most skills, it responds to deliberate effort.