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Brain scans reveal a shocking difference between psychopaths and other people

Date:

May 10, 2026

Source:

Nanyang Technological University

Summary:

Scientists have uncovered a striking brain difference linked to psychopathy: people with psychopathic traits were found to have a striatum — a brain region tied to reward, motivation, and decision-making — that was about 10% larger on average than those without such traits. Using MRI scans and psychological assessments on 120 participants, researchers connected this enlarged brain region to thrill-seeking, impulsive behavior, and a stronger drive for stimulation.

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Scientists may have uncovered a hidden brain difference that helps explain the thrill-seeking behavior of psychopaths. Credit: AI/ScienceDaily.com

Neuroscientists have identified a measurable brain difference between people with psychopathic traits and those with few or none. In a study published in the Journal of Psychiatric Research, researchers from Nanyang Technological University, Singapore (NTU Singapore), the University of Pennsylvania, and California State University found that a brain region involved in reward and motivation was larger in individuals with psychopathic traits.

Using magnetic resonance imaging (MRI), the team found that the striatum was about 10 percent larger on average in psychopathic individuals compared with a control group. The striatum sits deep in the forebrain and plays a role in movement planning, decision-making, motivation, reinforcement, and how the brain responds to rewards.

Psychopathy is generally associated with an egocentric and antisocial personality pattern. People with strong psychopathic traits often show reduced empathy, little remorse for harmful actions, and, in some cases, a greater likelihood of criminal behavior. Not everyone with psychopathic traits commits crimes, and not every person who commits a crime is a psychopath, but research has consistently linked psychopathy with a higher risk of violent behavior.

A Larger Reward Center in the Brain

Earlier research had suggested that the striatum may be unusually active in psychopaths, but it was less clear whether the size of this brain region was also involved. The Journal of Psychiatric Research findings added evidence that psychopathy is not shaped only by social and environmental experiences. Biology may also play a role.

To investigate the link, the researchers scanned the brains of 120 people in the United States. They also interviewed the participants using the Psychopathy Checklist -- Revised, a widely used psychological assessment designed to measure psychopathic traits.

Assistant Professor Olivia Choy, from NTU's School of Social Sciences, a neurocriminologist who co-authored the study, said: "Our study's results help advance our knowledge about what underlies antisocial behavior such as psychopathy. We find that in addition to social environmental influences, it is important to consider that there can be differences in biology, in this case, the size of brain structures, between antisocial and non-antisocial individuals."

The findings may help researchers better understand how biology contributes to antisocial and criminal behavior. Over time, that knowledge could help refine theories of behavior and inform future approaches to policy, prevention, and treatment.

What the Striatum May Reveal About Risk and Reward

The striatum is part of the basal ganglia, a group of neuron clusters located deep in the brain. The basal ganglia receive information from the cerebral cortex, which helps control thinking, social behavior, and the ability to decide which sensory information deserves attention.

Over the past two decades, scientists have increasingly recognized that the striatum is not only involved in movement and reward. It may also be tied to social behavior and difficulties in social functioning.

By comparing MRI scans with psychopathy assessment results, the researchers found that a larger striatum was linked to a stronger need for stimulation, including thrill-seeking, excitement, and impulsive behavior. In the published study, stimulation-seeking and impulsivity partly explained the relationship between striatal volume and psychopathy, accounting for 49.4 percent of the association.

Professor Adrian Raine from the Departments of Criminology, Psychiatry, and Psychology at University of Pennsylvania, who co-authored the study, said: "Because biological traits, such as the size of one's striatum, can be inherited to child from parent, these findings give added support to neurodevelopmental perspectives of psychopathy -- that the brains of these offenders do not develop normally throughout childhood and adolescence."

Psychopathic Traits Outside Prison Populations

One important feature of the study was that it included people from the community rather than focusing only on