Scientists Discover A Striking Brain Difference In People With Psychopathic Traits

Brain imaging research has identified a significant structural difference in the brains of adults with psychopathic traits compared with other individuals. A multinational team of researchers reports that a key reward-related brain region, the striatum, is noticeably larger in people with higher psychopathy scores.

The study, published in the Journal of Psychiatric Research, used magnetic resonance imaging (MRI) to scan 120 adults in the United States. Participants also completed the Psychopathy Checklist–Revised, a widely used clinical assessment tool that measures traits such as lack of empathy, impulsivity and antisocial behavior.

On average, the striatum was approximately 10 percent larger in participants with stronger psychopathic traits than in those with lower scores. Located deep within the forebrain, the striatum plays an important role in movement planning, motivation, decision-making and reward processing.

Psychopathy describes a pattern of emotionally shallow, egocentric and antisocial behavior, often associated with reduced remorse and empathy. Although not all individuals with psychopathic traits engage in criminal behavior, research has consistently linked these traits to a higher risk of violence and persistent offending.

How The Reward System Appears To Differ

Earlier studies suggested that the striatum may be unusually active in people with psychopathic traits, particularly during reward anticipation. The new findings indicate that structural differences — not only altered activity — may also contribute to the stronger drive for stimulation and reward.

Researchers found that larger striatal volume was associated with greater sensation-seeking and impulsivity. Traits such as thrill-seeking and the constant pursuit of excitement explained nearly half of the connection between striatal size and psychopathy scores.

Because brain structure is partly shaped by genetics, the authors argue that the findings support a neurodevelopmental view of psychopathy. According to this perspective, the brains of individuals with elevated psychopathic traits may develop differently during childhood and adolescence.

Typically, the striatum gradually shrinks as the brain matures. An enlarged striatum in adulthood may therefore reflect altered developmental patterns that influence reward sensitivity and impulse control.

Moving Beyond Prison-Based Research

Much of the earlier brain research on psychopathy focused primarily on incarcerated populations, limiting how broadly the results could be applied. This study instead used a community sample, allowing researchers to examine psychopathic traits in individuals living in ordinary social settings rather than prisons.

The sample also included 12 women, offering relatively rare insight into psychopathic traits outside predominantly male offender populations. Researchers reported that psychopathy was associated with a larger striatum in both women and men, although they cautioned that the female sample was small and requires further replication.

The inclusion of women is important because psychopathy research has historically focused heavily on men, particularly male offenders. Detecting similar structural patterns in both sexes suggests that at least some underlying brain mechanisms may be shared.

At the same time, experts emphasize that a larger striatum does not predetermine violence or criminal behavior. Instead, it may represent one biological factor that interacts with upbringing, environment and life experiences to influence risk.

A Broader Network Of Brain Differences

More recent research has expanded the focus beyond a single brain region. A 2025 study published in European Archives of Psychiatry and Clinical Neuroscience examined 39 adult men diagnosed with psychopathy and found reduced volumes in several areas, including parts of the basal ganglia, thalamus, basal forebrain, pons, cerebellum, and frontal and insular cortices.

These differences pointed to disruptions in frontal-subcortical circuits involved in behavioral control, planning and emotional regulation. Such systems help people evaluate consequences, control impulses and adapt behavior appropriately in social situations.

Another 2025 meta-analysis published in Neuroscience and Biobehavioral Reviews combined data from 38 functional brain imaging studies of psychopathy. Despite methodological differences between studies, the findings converged on a broader network involving the brain’s default mode network and several subcortical structures.

Researchers involved in that review argued that psychopathy is best understood as a disorder affecting interconnected brain networks rather than a single isolated structure. Processes such as motivation, emotional regulation, moral reasoning and social cognition likely interact across this larger system.

Together, these findings add complexity to the enlarged striatum result. The reward-related differences remain an important clue, especially because of their connection to impulsivity and sensation-seeking, but they appear to form part of a broader pattern of structural and functional brain variation.

Genes, Development And Environment

Scientists are continuing to investigate why the striatum and related brain systems differ in some individuals. Genetic factors likely contribute, as many traits linked to psychopathy show moderate heritability and brain structure itself tends to run in families.

However, researchers stress that environment also strongly shapes brain development. Childhood neglect, trauma, inconsistent caregiving and adverse experiences can all affect how brain systems involved in reward processing, stress responses and empathy mature over time.

Some experts propose that psychopathic traits may emerge when heightened reward sensitivity combines with weak emotional bonding or limited early-life caregiving. In these situations, a biologically driven search for stimulation may develop in environments that fail to reinforce empathy and prosocial behavior.

Understanding these pathways could eventually support prevention and intervention strategies. Stable caregiving, emotional support and programs designed to strengthen social and emotional skills may help reduce the likelihood that biological vulnerabilities develop into severe antisocial behavior.

For now, researchers emphasize that brain imaging should not be used to label individuals or predict criminal behavior on its own. Current evidence mainly shows average group-level differences rather than definitive markers for any single person.

Future studies are expected to explore how genetics, childhood experiences and later life events interact to shape the brain systems involved in reward, empathy and self-control. Long-term research following children into adulthood may prove especially important for understanding how psychopathic traits develop over time.

Despite many unanswered questions, the growing body of evidence presents psychopathy as a complex condition shaped by both biological and environmental influences. By mapping how reward circuits and broader brain networks differ, scientists hope to develop more accurate theories and eventually more effective approaches to treatment and risk reduction.