"Psychopaths Have Different Brains" ... Reward and Motivation Regions Are 10% Larger

Analysis of Psychopathic Traits in 120 Adults

Striatum, the Brain Region Responsible for Reward and Motivation,

Found to Be on Average 10% Larger Than in the General Population

It has been found that individuals with psychopathic tendencies have larger brain regions responsible for reward and motivation compared to the general population. The research team suggested that impulsivity and sensation-seeking traits may be related to structural differences in the brain.

According to ScienceDaily on May 10, a joint research team from Nanyang Technological University (Singapore), Pennsylvania State University, and California State University (USA) published a paper in the Journal of Psychiatric Research stating, "Individuals with stronger psychopathic tendencies had a striatum—an area of the brain involved in reward and motivation—approximately 10% larger on average."

The research team conducted magnetic resonance imaging (MRI) scans and Psychopathy Checklist-Revised (PCL-R) interviews with 120 American adults.

The results showed that people with strong psychopathic tendencies had a larger average striatum size than the control group. The striatum, located deep within the forebrain, is involved in motor planning, decision-making, motivation, and reward response.

Psychopathy is generally associated with egocentrism and antisocial tendencies. It is characterized by a lack of empathy and a diminished sense of guilt for behaviors that harm others.

The research team explained that these findings suggest psychopathic traits are not formed solely by social or environmental factors. Olivia Choy, a professor at Nanyang Technological University and co-author of the study, said, "These results help us understand the underlying causes of antisocial behavior," adding, "It is necessary to consider not only social and environmental influences but also biological differences such as brain structure size."

The researchers also noted that the striatum may be involved not only in motor and reward functions but also in social behavior and social dysfunction. A comparison of MRI results and psychopathy assessments revealed that a larger striatum was associated with stronger tendencies toward thrill-seeking, excitement-seeking, and impulsive behaviors. The study found that sensation-seeking and impulsivity explained about 49.4% of the association between striatum size and psychopathic traits.

Adrian Raine, a professor at the University of Pennsylvania and co-author of the study, stated, "Biological characteristics such as striatum size can be inherited from parents," adding, "This supports the possibility that the brains of individuals with psychopathic tendencies may not develop typically during childhood and adolescence."

This study is also noteworthy in that it was conducted with members of the general community, not inmates in correctional facilities. Robert Schug, a professor at California State University, Long Beach and co-author, explained, "This approach helps us understand psychopathic tendencies in people living ordinary lives outside of prison."

The research team also analyzed data from 12 female participants. The results showed that the association between striatum enlargement and psychopathic tendencies was observed not only in men but also in women. However, they noted that the small sample size of female participants requires further research.

The researchers also pointed out that in typical development, the striatum tends to decrease in size as people grow. Based on this, they suggested that psychopathic tendencies may be related to differences in brain development during childhood and adolescence. Professor Choy stated, "Psychopathic tendencies may be associated with structural abnormalities in the brain that emerge during development," but also emphasized, "We must also consider that the environment can influence the structure of the striatum."

Professor Raine explained, "It is well known that people with psychopathic tendencies have an extreme drive to pursue actions that yield rewards, such as property crimes, sexual offenses, and substance abuse," adding, "This study provides a neurobiological basis for such impulsive and sensation-seeking behavior."