Psychopaths have a VERY different brain size to the rest - and it's not what you think

Psychopaths have markedly different brain structures to the rest of the population, a major study has found-offering fresh insight into one of the darkest corners of human psychology, reports Newsweek.

Experts published in Springer Nature say the findings shed new light on the neurobiology behind aggression and violent behaviour, with the results confirming long-suspected links between brain volume and psychopathic traits.

Dark personality triad

A team of scientists from Germany and the University of Pennsylvania used cutting-edge neuroimaging techniques alongside the publicly available Julich-Brain Atlas to compare the brains of 39 adult men diagnosed with psychopathy to a group of control subjects.

The research, which focused on the so-called "dark personality" triad, found striking differences in brain volume and structure, particularly in regions associated with emotion, decision-making and behavioural control.

Psychopathy Check-List

Participants were evaluated using the Psychopathy Check-List, a widely used diagnostic tool. Those with higher scores in "lifestyle and antisocial behaviour" showed significantly lower brain volume in key areas, including the basal ganglia-linked to motor control and learning-and the thalamus, which relays sensory information.

Further reductions were seen in the brainstem and cerebellum, which help regulate coordination and movement, as well as in the orbitofrontal and insular regions, areas central to emotional regulation and social interaction.

The researchers said these findings suggest that the neural circuits responsible for controlling behaviour may be underdeveloped or impaired in people with psychopathic tendencies.

Interestingly, traits such as pathological lying and lack of empathy-described in the study as "interpersonal-affective" aspects-were not as strongly correlated with brain structure as the antisocial behavioural traits.

Significantly lower brain volume

The team also found that overall brain volume was significantly lower in the psychopathy group compared to the controls, with the most notable difference found in the right subiculum, a part of the hippocampus involved in memory.

The findings point to what the researchers called a "widespread disturbance of brain development" in individuals with psychopathic traits. They concluded that there is "a particularly strong neurobiological link between antisocial behaviour and reduced brain volume across widespread regions."

However, the authors did note some limitations, such as the use of different MRI scanners, which was accounted for statistically, and the fact that participants were not matched for cognitive ability or substance use-both of which could have influenced results.

Even so, the study marks a significant step forward in understanding the biology of violent and antisocial behaviour, with future research likely to explore whether these brain differences are genetic or influenced by the environment.