Scientists Have Established a Key Biological Difference Between Psychopaths and Normal People

According to a new study, psychopathic individuals have a larger striatum region in their brain.

Psychopathic persons have a 10% bigger striatum, a collection of neurons in the subcortical basal ganglia of the forebrain, than typical people, according to neuroscientists who used MRI scans. This is a definite biological differential between psychopaths and non-psychopathic individuals.

A biological differential between psychopaths and non-psychopaths has been revealed by neuroscientists from Nanyang Technological University (NTU Singapore), the University of Pennsylvania, and California State University. Scientists revealed that the striatum, a forebrain region, was 10% larger in psychopathic persons compared to a control group of people with mild or no psychopathic features using magnetic resonance imaging (MRI) scans.

People with psychopathic tendencies, often known as psychopaths, have an arrogant and antisocial personality. This is marked by a lack of responsibility for their acts, a lack of empathy for others, and, in some cases, criminal inclinations.

The striatum, which is part of the forebrain, the cerebrum's subcortical area, coordinates many aspects of cognition, including motor and action planning, decision-making, motivation, reinforcement, and reward perception.

Psychopaths have a hyperactive striatum, according to previous studies, but the effect of its size on behavior has yet to be established. A major biological difference exists between persons who have psychopathic inclinations and those who do not, according to new study. While not all persons with psychopathic characteristics end up breaking the law, and not all criminals meet the psychopathy requirements, there is a strong link. Psychopathy is also linked to more aggressive conduct, according to the findings.

Understanding the role of genetics in antisocial and criminal conduct may assist to strengthen existing behavioral theories as well as guide policy and treatment alternatives. The neuroscientists used the Psychopathy Checklist-Revised, a psychological evaluation instrument to detect the existence of psychopathic tendencies in individuals, to scan the brains of 120 volunteers in the United States and interview them.

“Our study’s results help advance our knowledge about what underlies antisocial behavior such as psychopathy. We find that in addition to social environmental influences, it is important to consider that there can be differences in biology, in this case, the size of brain structures, between antisocial and non-antisocial individuals," said Assistant Professor Olivia Choy, a neurocriminologist from NTU's School of Social Sciences who co-authored the paper.

“Because biological traits, such as the size of one’s striatum, can be inherited to a child from a parent, these findings give added support to neurodevelopmental perspectives of psychopathy – that the brains of these offenders do not develop normally throughout childhood and adolescence,” said co-author Professor Adrian Raine of the University of Pennsylvania's Departments of Criminology, Psychiatry, and Psychology.

“The use of the Psychopathy Checklist-Revised in a community sample remains a novel scientific approach: Helping us understand psychopathic traits in individuals who are not in jails and prisons, but rather in those who walk among us each day,” according to Professor Robert Schug from the School of Criminology, Criminal Justice, and Emergency Management at California State University, Long Beach, who co-authored the study.

The study's findings were just published in the peer-reviewed academic journal Journal of Psychiatric Research.

Bigger striatum, larger appetite for stimulation

The researchers associated having a bigger striatum to an increased demand for stimulation, such as thrills and excitement, as well as a higher risk of impulsive actions, based on analysis of the MRI scans and results from the interviews used to screen for psychopathy.

The striatum is a portion of the basal ganglia, which is a network of neurons deep in the brain's center. The cerebral cortex sends impulses to the basal ganglia, which governs cognition, social behavior, and determining whether sensory information requires attention.

However, in the last two decades, our knowledge of the striatum has grown, revealing that it is associated to social behavior problems. Previous research has not looked into whether adult females with psychopathic tendencies had striatal hypertrophy.

According to the neuroscientists, they evaluated 12 females in their research of 120 people and discovered, for the first time, that psychopathy is associated to a larger striatum in both men and women. As a kid grows older, the striatum shrinks, implying that psychopathy may be linked to changes in brain development.

“A better understanding of the striatum’s development is still needed. Many factors are likely involved in why one individual is more likely to have psychopathic traits than another individual. Psychopathy can be linked to a structural abnormality in the brain that may be developmental in nature. At the same time, it is important to acknowledge that the environment can also have effects on the structure of the striatum,” Asst Prof Choy stated.

“We have always known that psychopaths go to extreme lengths to seek out rewards, including criminal activities that involve property, sex, and drugs. We are now finding out a neurobiological underpinning of this impulsive and stimulating behavior in the form of enlargement to the striatum, a key brain area involved in rewards," Prof Raine continued.

The researchers intend to do more study to learn more about the reasons of striatum enlargement in those who have psychopathic characteristics.