Study Finds People with Higher Psychopathy Scores Have Larger Striatum
New research reports a measurable brain difference associated with psychopathic traits: adults who score higher on psychopathy measures show an approximately 9% larger corpus striatum. The striatum is a deep brain structure involved in translating motivation into action, evaluating rewards, decision-making, and some aspects of social behavior.
A team of researchers from Nanyang Technological University (Singapore), the University of Pennsylvania and California State University, Long Beach analyzed structural MRI scans from 120 community volunteers in the Greater Los Angeles area (108 men and 12 women). Their findings were published in the Journal of Psychiatric Research under the title "Larger striatal volume is associated with increased adult psychopathy."
Methods and key findings
Before testing the main association, the investigators examined potential confounders including age, total brain volume, prior head injury, race, ADHD, substance use, and social adversity. They reported that race and past head injury did not meaningfully change the results, while age, ADHD, substance use, social adversity and overall brain size had measurable effects and were statistically controlled for in subsequent analyses.
After adjustment for these factors, individuals with higher psychopathy scores exhibited roughly a 9% larger striatal volume compared with those with lower scores. The authors also found that impulsivity and thrill-seeking partially mediated the relationship between larger striatal volume and psychopathic traits, suggesting a possible behavioral pathway linking anatomy to observed tendencies.
Implications and limitations
The study's authors suggest that a relatively enlarged striatum might predispose some people toward impulsive, reward-seeking behavior, which could help explain part of the association between brain anatomy and psychopathic traits. They note potential clinical relevance: while the colloquial term "psychopath" is not a formal diagnosis, better knowledge of brain–behavior relationships could inform targeted psychotherapeutic approaches or adjunctive pharmacological strategies in treating antisocial or related behaviors.
However, several limitations temper the conclusions. The study is cross-sectional, so it cannot establish causality (larger striatum may be a cause, consequence, or correlate of behavioral traits). The sample included only 12 female participants, limiting conclusions about sex differences, and all participants were drawn from one metropolitan area, which may affect generalizability. The authors call for replication in larger, diverse samples and longitudinal work to clarify developmental pathways.
Takeaway: This study adds evidence that structural brain differences—in this case, an enlarged striatum—are associated with higher psychopathy scores and with traits such as impulsivity and thrill-seeking, but causality and broader applicability remain to be established.
