Neuroscientists have pinpointed a potential biological signature for psychopathy

A recent study has found that high levels of psychopathic traits are associated with reduced thickness in specific outer layers of the brain responsible for processing emotions and guiding decision-making. These neural patterns appear consistently in men with high psychopathic traits, regardless of whether they have a history of committing domestic violence. The study was published in the journal Aggression and Violent Behavior.

Psychopathy is a complex psychological concept characterized by traits like callousness, manipulation, impulsivity, and a lack of remorse. It is widely recognized as a risk factor for various forms of violence, including intimate partner violence. Scientists have sought to establish the biological markers of psychopathy by linking specific brain structures to these manipulative and antisocial traits.

A clear biological marker could help clinicians define the condition more accurately and improve forensic evaluations. Past studies have produced mixed results regarding the exact brain regions involved in psychopathy. The researchers conducted this study to summarize past findings and test these brain-psychopathy links in a specific group of men convicted of domestic violence.

“Psychopathy is a major risk factor for persistent violence, including intimate partner violence (IPV). Therefore, understanding the biological basis of these traits can help forensic practitioners create more accurate profiles by combining psychological assessments with neuroimaging. Additionally, as broader our knowledge to establish objective brain correlates, better our ability for adequately define psychopathy as a psychological construct,” said study author Ángel Romero-Martínez, a professor of psychobiology at the University of Valencia.

The researchers also wanted to see if the relationship between psychopathic traits and brain thickness differed between violent offenders and men with no history of violence. To begin, the scientists conducted a systematic review of twenty-nine past studies. They focused on research examining the thickness and volume of the cerebral cortex, which is the wrinkled outer layer of the brain involved in high-level functions like thought and emotion.

This review helped them identify specific brain areas that consistently show structural differences in individuals with psychopathic traits. One major area was the orbitofrontal cortex, a region situated just behind the eyes that helps guide decision-making. Another frequently implicated area was the insula, located deep within the brain and tied to emotional processing and empathy.

Following the review, the scientists conducted an empirical study involving 125 men in Valencia, Spain. The sample included 67 men convicted of intimate partner violence who had received prison sentences of less than two years. These men were participating in a mandatory community psychological intervention program as an alternative to finishing their sentences in prison.

The remaining 58 participants were community controls with no criminal records and no history of violent behavior. To verify their non-violent history, the researchers had these men complete a conflict tactics questionnaire, ensuring they scored zero on psychological aggression, physical assault, and sexual coercion. The scientists also screened all participants to confirm they had no severe mental or physical disorders.

To measure intelligence, the researchers administered a brief cognitive test, requiring all participants to have an intelligence quotient of eighty or above. To measure psychopathic traits, trained interviewers administered the Psychopathy Checklist-Revised. This involved a detailed forty-five-minute interview and a review of the participants’ personal files to score their traits on a specific scale.

This psychological tool divides psychopathy into two main categories. Factor 1 covers interpersonal and affective traits like emotional coldness, grandiosity, and a lack of remorse. Factor 2 covers antisocial lifestyle traits like poor behavioral control, impulsivity, and a history of juvenile delinquency.

The researchers then used high-powered magnetic resonance imaging scanners to take high-resolution, three-dimensional images of each participant’s brain. The scanning process took about six minutes per person and required them to remain completely still. They used specialized software to measure the exact thickness of the cerebral cortex in the specific regions identified during their initial systematic review.

To isolate the effect of psychopathy, the scientists controlled for several outside variables that might independently influence brain thickness. These variables included age, educational level, total intracranial volume, and whether the participant was right or left-handed. They also controlled for a history of alcohol or drug misuse, utilizing specific dependency scales to account for substances like cocaine and cannabis.

The results indicated that across the entire sample of 125 men, higher psychopathy scores were linked to reduced cortical thickness in several specific brain regions. These regions included the left orbitofrontal cortex, the bilateral superior frontal gyrus, the left insula, the right anterior cingulate, and the right dorsomedial prefrontal cortex. The superior frontal gyrus helps restrain actions by anticipating behavioral consequences, while the anterior cingulate processes social information and weighs the costs and benefits of an action.

The reduced thickness in these areas suggests why individuals with high psychopathic traits struggle to integrate their thoughts and emotions. This neural difference tends to lead to poor decision-making and an inability to adapt behavior based on future consequences. When analyzing the different types of psychopathic traits, the researchers found that the interpersonal and affective traits of Factor 1 were most consistently linked to reductions in these specific frontal brain regions.

“The reduced thickness in areas like the orbitofrontal cortex and the insula, among others, may explain why individuals with these traits struggle to integrate thoughts and emotions, leading to poor decision-making and impaired goal-directed behavior,” Romero-Martínez told PsyPost.

“Practically, these findings provide a ‘biological signature’ that can complement self-reports, potentially improving the accuracy of forensic evaluations. But it is necessary to be cautious with these conclusions as it is completely necessary to conduct additional research to better understanding this link and their practical applications.”

When the researchers compared the two groups, they found that the link between psychopathy and brain thickness was identical for both the intimate partner violence perpetrators and the community controls. The biological signature of psychopathy remained consistent regardless of an individual’s criminal history. This suggests that the observed brain structure differences are a general characteristic of psychopathic traits, rather than being uniquely tied to the act of domestic violence itself.

“We initially expected that the link between cortical thickness and psychopathy were specific of IPV perpetrators, but group (IPV perpetrators or controls) did not significantly change the association between psychopathic traits and cortical thickness,” Romero-Martínez noted. “Therefore, the association remained consistent across the entire sample (both groups together).”

While the findings are informative, the researchers caution against a strict localizationist view, which assumes psychopathy is controlled by a single isolated brain region. Different aspects of psychopathy are linked to various brain areas, meaning the condition arises from a complex network of regions rather than one specific spot.

“It is important not to view psychopathy as a single, uniform trait,” Romero-Martínez explained. “The research shows that different brain regions may be more specifically linked to one factor than the other — for instance, Factor 1 is more consistently linked to reductions in the orbitofrontal cortex. Nonetheless, this does not mean that the psychopathy was explained only by a single brain region.”

The study also has some limitations, including its cross-sectional design, which means it cannot prove that these brain structures directly cause psychopathic behavior. Additionally, the sample was relatively homogeneous, consisting entirely of adult Spanish men without severe mental health conditions. Future research should include larger and more diverse samples to confirm these findings and explore how these structural brain differences develop over time.

“The long-term goal is to use neuroimaging to help develop more precise diagnostic and forensic profiles, which in turn, might help to develop specific and effective intervention programs,” Romero-Martínez explained. “By identifying the ‘fronto-temporo-parietal’ network as being particularly relevant, the study guides future research to focus on these specific structures to better understand the complexity of the psychopathy construct.”

“I would like to emphasize that this study is, of course, the result of a collective effort involving many dedicated colleagues. This research was made possible through the collaboration of researchers from the Department of Psychobiology (Luis and Carolina) Department of Social Psychology at the University of Valencia (Marisol) and the Biomedical Imaging Research Group (GIB1230) at the La Fe Health Research Institute (María, Fernando, Leonor and Luis).”

The study, “Reduced cortical thickness in fronto-temporo-parietal regions associated with high psychopathic traits: Conclusions of a review and an empirical study with intimate partner violence perpetrators,” was authored by Ángel Romero-Martínez, María Beser-Robles, Leonor Cerdá-Alberich, Fernando Aparici, Luis Martí-Bonmatí, Carolina Sarrate-Costa, Marisol Lila, and Luis Moya-Albiol.