The Anatomy Of Psychopathy: Antisocial Traits Seen By Brain Imaging

Psychopathy is a personality trait associated with emotional coldness, lack of empathy, and impulsive and aggressive behavior. Studies show that people with psychopathic traits have differences in several areas of the brain, especially in the regions that control emotions, impulses, and decisions. These changes help explain why these people tend to act without guilt or remorse and are at greater risk of engaging in and repeating crimes.

Psychopathy is a complex personality condition that has been widely studied for its strong link to aggressive and violent behavior. People with psychopathic traits tend to engage in more criminal acts, cause more harm to others, and are more likely to repeat these behaviors over time.

This not only places a great financial cost on society through the justice system, prisons, and treatment, but also imposes considerable suffering on victims.

Despite the severity of the impacts of psychopathy, it is still not officially classified as a specific disorder in the most widely used diagnostic manuals, such as the ICD-10 or the DSM-5. It shares some characteristics with antisocial personality disorder, but they are not exactly the same thing. 

To identify psychopathic traits, mental health and criminal justice professionals often use an instrument called the PCL-R (Hare Psychopathy Checklist). This tool assesses psychopathy in two broad groups of traits: one related to emotions and social interactions (factor 1) and the other to impulsive and antisocial behaviors (factor 2).

The PCL-R (Hare Psychopathy Checklist) is a tool created by Canadian psychologist Robert Hare and used primarily by mental health professionals in clinical and forensic settings (such as prisons or courts) to assess whether a person displays psychopathic traits.

The test is administered through structured clinical interviews and analysis of personal and court documents, and contains 20 items that assess behaviors and personality traits, such as lack of empathy, manipulation, impulsivity, constant lying, and antisocial behavior. Each item is scored from 0 to 2, resulting in a total score of up to 40 points.

The higher the score, the stronger the psychopathic traits. Generally, a score of 30 or higher (in countries like the US) indicates clinical psychopathy. The test is also divided into two main factors: the first assesses emotional and interpersonal traits (such as emotional coldness and superficial charm), and the second assesses lifestyle and antisocial behaviors (such as impulsivity and criminality).

Factor 1 is linked to characteristics such as lack of empathy, lack of guilt, superficial charm and emotional coldness. People who score high on this factor may appear charming and confident, but they are manipulative and emotionally distant. They tend to react little to emotional stimuli and have low anxiety, which may explain their coldness in serious situations.

Factor 2 describes more visible and impulsive behaviors, such as aggression, irresponsibility, addictions and early criminal behavior. These people tend to have an unstable lifestyle and make rash decisions without thinking about the consequences.

Although the two factors make up psychopathy as a whole, they reflect different ways of psychological functioning and possibly originate in different parts of the brain.

Researchers use brain imaging tests, such as magnetic resonance imaging (MRI), to try to identify which parts of the brain are involved in these traits. In previous studies, the results have not always been consistent, in part because the sample sizes were small and the individuals were very different from each other.

Still, it has been observed that people with psychopathic traits tend to have differences in the volume of gray matter, the brain tissue where the most complex mental processes occur, especially in regions such as the prefrontal cortex, amygdala and hippocampus, which are involved in decision-making, emotions and memory.

Studies have shown that factor 1 (emotional and interpersonal) is generally associated with reduced volume in areas such as the prefrontal cortex and orbitofrontal cortex, as well as regions of the temporal lobe, where the amygdala and hippocampus are located.

These findings suggest that people with this profile may have more difficulty feeling and processing emotions, such as empathy and guilt. Factor 2 (impulsive and antisocial behavior) is related to brain areas linked to impulse control and rewards, such as the putamen, insula and orbitofrontal cortex.

Some studies have even found an increase in volume in these regions, which may indicate a functional difference in these structures. However, other studies show just the opposite, a reduction in volume, and some have found no relationship at all. In other words, there is still no scientific consensus on how this factor manifests itself in the brain.

A meta-analysis (a study that combines data from several other studies) has reinforced the idea that factor 1 is linked to decreases in areas of the brain associated with emotional control and empathy, while factor 2 appears to be linked to a wide range of regions involved in impulsive behavior.

However, researchers still face many challenges, such as the small number of studies available, the difficulty of finding and studying volunteers with high levels of psychopathy (especially among criminals), and the presence of other disorders that can interfere with the results.

In the most recent study, conducted by researchers at the Institute of Neuroscience and Medicine (INM-1) in Germany, the brains of 39 men with high levels of psychopathic traits were analyzed, comparing them with individuals without these traits, using magnetic resonance imaging and specific tools to measure brain volumes. 

This figure shows which parts of the brain are associated with factor 1 of psychopathy, which involves interpersonal and affective characteristics such as emotional callousness, lack of empathy, and superficial charm. Areas highlighted in blue represent regions where the greater the psychopathy, the smaller the brain volume (negative association), and areas highlighted in red and yellow indicate positive associations (i.e., greater psychopathy is linked to larger volumes). The technical names refer to specific parts of the brain, such as the orbitofrontal cortex, temporal lobe, and cerebellum, which are linked to controlling emotions, judgment, and decision-making. These changes in volume help scientists understand which areas of the brain may function differently in people with high psychopathic traits.

The analysis revealed that factor 2, impulsive and antisocial behavior, was linked to reduced volume in several brain regions, including the pons, thalamus, basal ganglia, and areas in the frontal cortex and insula. These regions are strongly linked to controlling impulses, emotions, and planned behavior.

Associations of PCL-R factor 2 (deviant lifestyle and antisocial behavior) with volumes of brain regions in psychopathic individuals with PCL-R total ≥ 20.

Factor 1 showed only small and inconsistent associations with some brain regions, such as the hippocampus and areas of the frontal cortex, which suggests that this aspect of psychopathy may manifest itself in a more varied way among different people.

The comparison between the psychopathic group and the control group indicated that psychopaths had, in general, a smaller total brain volume, with a more marked difference in the right subiculum, an area linked to memory and emotional control.

Group differences in brain region volumes between psychopathic individuals with PCL-R total ≥ 20 (PS) and healthy controls (C). Volume data were adjusted for study (acquisition site), age, and intracranial volume. Box plots show individual data points.

In summary, the study reinforces the idea that psychopathy is not a single condition, but rather a set of distinct traits involving multiple brain regions. The antisocial behavior factor appears to be most strongly associated with specific brain changes, while the emotional/interpersonal factor shows greater variation across individuals.

These results help to better understand the biological basis of psychopathy and may, in the future, guide more effective prevention and treatment strategies.

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Associations of brain structure with psychopathy. 

Peter Pieperhoff, Lena Hofhansel, Frank Schneider, Jürgen Müller, Katrin Amunts, Sabrina Weber-Papen, Carmen Weidler, Benjamin Clemens, Adrian Raine, and Ute Habel 

Eur Arch Psychiatry Clin Neurosci (2025). 

https://doi.org/10.1007/s00406-025-02028-6

Abstract: 

Psychopathy is one of the greatest risk factors for serious and persistent violence. In order to detect its neurobiological substrates, we examined 39 male psychopathic subjects and matched controls using structural MR imaging and the Psychopathy Check-List (PCL-R). Individual brain region volumes were calculated using the Julich-Brain and AAL3 atlases. Associations of region volumes with the PCL-R dimensions among psychopathic subjects and differences between both groups were analysed. PCL-R factor 2 assessing lifestyle and antisocial behaviour showed in the psychopathic sample negative associations with volumes of several regions, including pons, nuclei of basal ganglia, thalamus, basal forebrain (CH-4), cerebellar regions and areas in orbitofrontal, dorsolateral-frontal and insular cortices. These findings suggest dysfunctions in specific frontal-subcortical circuits, which are known to be relevant for behavioral control. In contrast, the interpersonal-affective PCL-R factor 1 showed only weak positive and negative associations with orbitofrontal, dorsolateral-frontal and left hippocampal areas (CA1, subiculum), among others, indicating that involved brain regions might be affected to a variable degree in different individuals. The group comparison yielded a significantly reduced total brain volume in psychopathic subjects relative to controls, while pronounced regional focuses of volume differences were found only in the right subiculum, suggesting an interindividually variable pattern of structural deviations in the brains of psychopathic subjects. In conclusion, these findings are compatible with the dimensionality of the PCL-R construct, and suggest a particulary strong association of antisocial behavior to smaller volumes in widespread subcortical-cortical brain regions.