Brain Scans Link Psychopathy to Expanded Cortical Surface Area

A study of more than 800 incarcerated men has identified a link between high levels of psychopathy and specific structural anomalies in the brain, specifically an expanded cortical surface area and a compressed organizational layout of brain tissue. The findings, published in the journal Biological Psychiatry: Global Open Science, suggest that the biological roots of psychopathy may be more complex than previously understood by examining cortical thickness and surface area as distinct anatomical features.

The research was led by Marcin A. Radecki, who is affiliated with the University of Cambridge and the IMT School for Advanced Studies Lucca. He worked in collaboration with senior researchers Luca Cecchetti of the IMT School for Advanced Studies Lucca and Kent A. Kiehl of the Mind Research Network.

Distinguishing Cortical Surface Area and Thickness

Historically, neuroimaging research into psychopathy has focused on overall gray matter volume. Gray matter consists of the brain’s nerve cell bodies and is responsible for processing information, while white matter serves as the communication network connecting different brain regions.

However, the researchers noted that overall gray matter volume is a combination of two separate anatomical properties: cortical thickness, which is the depth of the brain’s outer layer, and surface area, which is the total expanse of the folded brain tissue. Because these two properties are influenced by different genetic factors and develop differently throughout a person’s life, analyzing them separately provides a more precise biological map of psychological traits.

Study Methodology and Participant Data

The team analyzed data from 804 adult men incarcerated in correctional facilities across the midwestern and southwestern United States. To achieve this sample size, researchers utilized a mobile scanner, which allowed them to conduct brain scans in a correctional setting rather than relying on traditional hospital environments.

To categorize the participants, the researchers used two primary assessment tools:

• The Interpersonal Reactivity Index: A standardized self-report questionnaire used to measure empathy. This tool allowed the team to generate specific scores for perspective taking (cognitive empathy) and empathic concern (the emotional ability to feel sympathy for others).
• The Psychopathy Checklist-Revised: A diagnostic tool based on clinical interviews and institutional file reviews. This index measures interpersonal and affective traits—such as grandiosity, superficial charm, and a lack of remorse—as well as lifestyle and antisocial behaviors.

Findings on Psychopathy and Empathy

The analysis revealed that individuals scoring high for psychopathy exhibited an expanded brain surface area combined with a compressed organizational layout of the brain tissue. This structural profile differs from the general focus on gray matter volume reductions often cited in earlier research.

The study emphasizes that empathy is not a single trait but a collection of distinct psychological skills. Cognitive empathy involves understanding another person’s mental state, while empathic concern involves an emotional response to another’s well-being. The research links the lack of these specific empathic traits to the observed structural properties of the cortical surface.

By separating the analysis of surface area from cortical thickness, the researchers were able to identify a more nuanced biological signature associated with the manipulation, impulsivity, and antisocial behavior characteristic of clinical psychopathy.