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Individuals with high levels of psychopathy tend to struggle with feeling concern for others, and new research links these psychological traits to specific structural properties of the brain. A recent analysis of brain scans from over 800 incarcerated men reveals that those scoring high for psychopathy possess an expanded brain surface area and a compressed organizational layout of their brain tissue. The resulting paper appears in the journal Biological Psychiatry: Global Open Science.
Empathy is not a single characteristic. It involves several distinct psychological skills that allow people to navigate social situations. Cognitive empathy allows a person to actively understand the perspective or mental state of someone else. Empathic concern is the emotional ability to actually feel sympathy or care for another person’s well-being.
In clinical psychology, psychopathy is typically characterized by a severe lack of these empathic traits. It is also distinctively categorized by high levels of manipulation, impulsivity, and antisocial behavior. Historically, researchers seeking to understand the biological roots of psychopathy have examined the physical structure of the brain.
Most previous imaging studies looked at overall gray matter volume. Gray matter is the darker tissue of the brain that contains the main bodies of nerve cells. It handles the processing of information, in contrast to white matter, which acts as the communication cables connecting different regions.
Overall gray matter volume is a combination of two distinct anatomical features. These features are cortical thickness, which refers to the ultimate depth of the brain’s outer layer, and surface area, which describes the total expansive sheet of the folded brain tissue. Because these two structural properties develop differently during a person’s life and are influenced by different genetic factors, looking at them separately can yield a much more precise biological picture.
To build a detailed map of how empathy and psychopathic traits align with brain anatomy, lead author Marcin A. Radecki worked alongside senior researchers Kent A. Kiehl and Luca Cecchetti. Radecki holds affiliations with the University of Cambridge and the IMT School for Advanced Studies Lucca. Kiehl operates through the Mind Research Network, and Cecchetti conducts research through the IMT School for Advanced Studies Lucca.
The team wanted to evaluate an exceptionally large sample of participants to find specific associations between empathy profiles, psychopathic behavior, and the physical shape of the brain. They gathered data from 804 adult men incarcerated in correctional facilities across the southwestern and midwestern United States. The mobile scanner allowed researchers to reach a much larger population of incarcerated individuals than would normally be possible in a traditional hospital setting.
To evaluate empathy levels in these men, the team relied on a standardized self-report questionnaire called the Interpersonal Reactivity Index. This survey asked participants to rate how well certain statements described them. The process generated specific scores for both perspective taking and empathic concern.
The team also calculated a formal score for psychopathy using detailed diagnostic clinical interviews and institutional file reviews. This standard assessment index is known as the Psychopathy Checklist-Revised. The diagnostic tool is broken down into two main structural categories.
One category measures interpersonal and affective traits. These include characteristics like superficial charm, grandiosity, and a persistent lack of remorse. The other category captures lifestyle and antisocial traits, including behaviors like impulsivity, irresponsibility, and a documented history of widespread criminal behavior.
Finally, the researchers utilized the mobile magnetic resonance imaging scanner brought directly to the correctional facilities to capture detailed pictures of each participant’s brain. By processing these brain scans with specialized analytical software, they could calculate the exact thickness and surface area of the brain’s outer tissue. The software divided the brain into hundreds of tiny parcels to allow for highly detailed regional mapping.
In analyzing the psychological data, the researchers found divergent, distinct relationships between the different forms of empathy and the categories of psychopathy. The interpersonal and affective psychopathic traits were uniquely linked to lower empathic concern. In contrast, the antisocial and lifestyle traits were uniquely associated with an impaired ability to take another person’s perspective.
The brain imaging results offered surprising insights into the physical structure of the cerebral cortex. Men who met the clinical threshold for high psychopathy possessed an increased total surface area of the brain. This structural expansion was particularly prominent in specific regions of the brain dedicated to social and emotional processing.
These brain areas included the superior temporal region and the auditory cortex, alongside regions belonging to the paralimbic system. The paralimbic system acts as a highly integrated bridge between the brain’s emotional centers and its higher-level cognitive structures. Changes in these regions matched up strongly with prior established templates of how the brain handles social interactions and sensory processing.
These physical brain structure differences were strictly related to the psychopathy scores and were not directly associated with the self-reported empathy survey scores. The discovery of an expanded surface area stands in direct contrast to some past anatomical imaging studies. Earlier research often reported reductions in overall brain volume among highly psychopathic individuals.
The authors suggest that separating out surface area from generalized volume provides a highly sensitive measurement of antisocial traits. Surface area is driven by different cellular mechanisms during brain development, such as how nerve cells migrate and fold into ridges over time. These underlying developmental mechanisms operate independently of the factors that determine the actual thickness of the cortical layer.
Beyond taking regular measurements of area and thickness, the team also investigated the macroscale organization of the brain using structural gradients. The brain is organized along continuous topographical maps that represent a transitional space. These maps span from primary sensory areas, which handle basic senses like vision and movement, all the way to complex associative areas.
These gradients help scientists understand how structurally distinct the brain’s basic sensory functions are from its higher integrative processing centers. In the men with high psychopathy, this natural structural gradient of cortical thickness was visibly compressed. A compressed gradient indicates a reduced physical differentiation between the opposite ends of the brain’s organizational spectrum.
Essentially, the structural layout connecting different functional sensory and associative networks was less segregated and pulled closer toward a centralized average. The compression of brain gradients observed in these men mirrors findings seen in other major psychiatric conditions. Similar losses of structural differentiation have been documented in studies evaluating schizophrenia and depression.
The authors note several limitations to their current study that provide directions for continued investigation. Because empathy was assessed using a simple self-report questionnaire, the psychological scores might be influenced by a high degree of social desirability bias. The test subjects might have lacked the psychological awareness required to evaluate their own empathic deficits accurately.
A performance test that asks participants to recognize facial expressions or interpret tone of voice could potentially uncover stronger links to the actual structure of the cortex. The self-reported empathy data did not map onto the brain structures in a way that produced statistically sound correlations. The physical imaging results corresponding solely to the empathy questionnaire measurements were not statistically significant in the general analysis.
Additionally, the subjects in this project were exclusively incarcerated adult men. Differences in brain structure layout and basic empathetic capacity are known to vary between the sexes based on a variety of environmental and developmental factors. The researchers caution that these particular brain trait relationships might not generalize to women or to individuals with psychopathic traits living freely in the general population.
Future research should aim to include diverse populations outside of the correctional system to see if the anatomical patterns hold true universally. Scientists also need to investigate the actual microscopic cellular mechanisms that drive the folding and expansion of the brain during early growth. Understanding exactly how and why the cortical surface area expands in these individuals could eventually inform early treatment programs meant to foster empathy and reduce severe antisocial behaviors.
The study, “Cortical Structure in Relation to Empathy and Psychopathy in 800 Incarcerated Men,” was conducted by a large team of international researchers. It was authored by Marcin A. Radecki, J. Michael Maurer, Keith A. Harenski, David D. Stephenson, Erika Sampaolo, Giada Lettieri, Giacomo Handjaras, Emiliano Ricciardi, Samantha N. Rodriguez, Craig S. Neumann, Carla L. Harenski, Sara Palumbo, Silvia Pellegrini, Jean Decety, Pietro Pietrini, Kent A. Kiehl, and Luca Cecchetti.
