There are three extremely offensive although not pathological personality traits: Machiavellianism, narcissism, and psychopathy. People with Machiavellian traits have very cold and manipulative personalities. Narcissistic people have feelings of grandiosity, entitlement, and superiority in most things. Psychopathy is the absence of anxiety and empathy for others but strong thrill-seeking and impulsivity. These three traits are infamously known in the scientific literature as The Dark Triad (DT) (Paulhus & Williams, 2002). But even though these traits make people potential criminals and possibly dangerous, they are not considered psychologically impaired although their personal style is charming, manipulative, self-aggrandizing, and often exciting and always vengeful. They are on the border between being somewhat sick and very ill. Their personalities are bad, but they are not bad enough to be diagnosed with a personality disorder.
The nature of the Dark Triad syndrome has been much debated over the past several decades. Current neuropsychological studies are few, but a new study changes this with its study of the brains of 24 healthy male subjects with high DT scores and 27 with low DT scores using high-resolution structural magnetic resonance brain images.
Brain scan results were analyzed with voxel-based morphometry to compare the two groups on the DT traits. Results showed that those men with high DT had reduced gray matter volumes in the precentral gyrus extending to the dorsolateral frontal gyrus, and the cerebellar crus II.
Data was then subjected to a regression analysis which found negative associations between gray matter volume in the dorsolateral prefrontal cortex with both Machiavellianism and psychopathy. Lower gray matter volume in the anterior cingulate cortex was negatively associated with psychopathy and narcissism. Lower gray matter volume in the medial orbitofrontal cortex, insula, and superior temporal sulcus showed negative associations with narcissism. Lastly, lower gray matter was primarily found in regions associated with empathy and social cognition. These structural differences support the idea that distinct neural structures contribute to interpersonal functioning and the antisocial tendencies of people high in DT traits (Mielke et al., 2025).
Closing Thoughts
This study is significant not only for its content but that it is the first to compare high vs. low DT subjects. It’s also important because it contributes yet more evidence supporting the fact that neurobiology shapes character to a profound degree and is often greater than mediating social forces could ever hope to achieve.
Paul Shane, Ph.D., LMT
Director, Academic Content
References
Mielke, E., Neukel, C., Roth, C., Bertsch, K., Nüssel, F., & Herpertz, S. (2025). Common and distinct morphometric correlates of the Dark Triad traits: Machiavellianism, narcissism and psychopathy in health male sample. Journal of Neural Transmission, https://doi.org/10.1007/s00702-026-03147-7.
Paulhus, D. & Williams, K. (2002) The Dark Triad of personality: Narcissism, Machiavellianism, and psychopathy. Journal of Research in Personality 36(6), p. 556–563.