The Neurobiology and Superficial Traits of Psychopathy

This article examines the neurobiology and traits of psychopathy, through case studies and the discussion of diagnosis.


The word ‘psychopath’ can often be used as a throw-away term to describe someone violent and cruel, but this a minimised view on the disorder. Additionally, psychopathy tends to be confused with sociopathy – but in an interview with the psychologist Ramani Durvasula, PhD, she says “the key difference: a psychopath is born, and a sociopath is made.” (2). While psychopathy does have environmental factors, it also has a strong genetic component  – but interestingly, individuals can be genetically predisposed to having psychopathy, yet the disorder remains dormant unless exacerbated by external factors. However, psychopathy is more common than typically believed – as it is estimated to affect 1% of the global population and is observed to be more prevalent in men than women. Interestingly enough, psychopathy affects between 15 and 25% of the prison population worldwide, thus implying an association between mental illness and criminality (3).

Psychopathic Traits

Psychopathy is characterised by various personality traits and behaviours, especially a lack of empathy, impulsivity, pathological lying, manipulative behaviour, and high intelligence (1). The reduced empathetic response is considered to be the most common psychopathic trait and can be observed through a willingness to engage in anti-social behaviour, a disregard for the impacts of their actions on other people, and a decreased physiological response to emotional stimuli (3). The latter is believed to be due to hyporeactivity of the autonomic nervous system to stimuli in psychopathic individuals compared to non-psychopathic individuals. However, psychopathy in itself is not an ‘official’ psychiatric diagnosis, and instead the term Antisocial Personality Disorder is used instead.

(8)Further, psychopathy and sociopathy are frequently used interchangeably in the media and film especially – and while these conditions share similarities, there are several differences. The main connection between psychopathy and sociopathy is engagement in anti-social behaviour, for instance, physical violence, harassment, vandalism, and other more serious offences (9). Other key similarities include: aggression, deceitfulness, anti-social behaviour, irresponsibility, impulsivity, and a lack of remorse and guilt. As mentioned earlier, it is the consensus that psychopaths are born while sociopaths become so as a result of their environmental factors. Having difficulty forming emotional attachments is a common psychopathic trait, as well as appearing charming and trustworthy by others. As well, psychopaths tend to be more strategic when engaging in anti-social behaviour so as to minimise the risk to themselves – but have little or no feeling of guilt as to the repercussions of their actions for others. Sociopaths are generally more erratic than psychopaths, and act more impulsively. Like psychopaths, sociopaths can also struggle to form emotional attachments – but this is not the case for all.

The Neurobiology of Psychopathy

Psychopathy is also believed to be greatly associated with the amygdala, and it has been hypothesised that amygdalar changes could be a source of deficit processing of fear-related responses in psychopathic individuals (4). In an article entitled ‘Localization of deformations Within the Amygdala in Individuals With Psychopathy’ (5), research was carried out with the purpose to detect amygdalar anatomical abnormalities in psychopathic individuals. The study consisted of 27 individuals who were psychopathic, and their amygdalar volumes were determined using volumetric analysis and surface-based mesh modelling methods. This meant any regional surface abnormalities would be able to be detected. The results showed that the individuals with psychopathy had significantly lower bilateral volumes of the amygdala compared with the control group – 17.1% on the left and 18.9% on the right. As the amygdala is necessary to incite the feeling of fear and fear conditioning, abnormalities in this anatomical structure can explain a lack of fear conditioning and response to dangerous situations in psychopathic individuals. Moreover, another function of the amygdala is social interaction and moral reasoning – and when there are structural abnormalities in the amygdala, this can show why psychopaths can lack the ability to recognise emotions in others, as well as poor moral judgement. 

In addition, psychopathic individuals can present with dysfunction of the ventromedial prefrontal cortex (vmPFC), which can impair the function of emotion and emotion regulation (6). The neuroscientist Antonio Damasio carried out research to investigate the connection between damage to the vmPFC and various emotion and decision- making deficits. Associations were made between dysfunction of the vmPFC and diminished shame, guilt, and empathy, as well as irritability and irresponsibility. The findings of this study also showed that psychopaths and patients who had suffered damage to their vmPFC had reduced autonomic arousal to emotional stimuli – thus showing that there are neurological explanations behind the lack of fear and acknowledgement of consequence in psychopathic individuals.

Another region of the prefrontal cortex potentially involved in psychopathy is the anterior cingulate cortex (ACC). Activity in the ACC has been associated with functions such as pain, empathy, negative affect, and performance. Patients who had lesions of the ACC have been shown to often exhibited greater irritability than those without, in addition to social disinhibition (6).

The case of the railroad construction worker Phineas Gage in the 19th Century (7) can further build on the link between the dysfunction of or injury to the prefrontal cortex and psychopathic traits. In a horrific accident at the railroad, Gage had an iron rod shot at his head – this had the effect of damaging his prefrontal cortex. Gage survived, but the most notable effect of this accident was the substantial changes in his personality; before he had been kind and dependable, but then became impulsive, rude, and disrespectful. These changes helped to identify the function of the prefrontal cortex, and these new personality traits that Gage had are very similar to those with psychopathy. After a number of similar cases during the 20th Century with damage to the prefrontal cortex resulting in personality changes, the term ‘pseudopsychopathy’ was coined to describe this association.

Diagnosis of a Psychopath

An important diagnostic tool for psychopathy is the Hare psychopathy checklist, created by the psychologist Dr Robert Hare (11). This checklist has been revised and is now formally known as the Hare PCL-R (Hare Psychopathy Checklist – Revised). In the PCL-R, there is an interview and a review of the patient’s history as two separate parts. The PCL-R evaluates to what extent an individual fulfils twenty psychopathic traits, such as lacking remorse or guilt, and having a grandiose sense of self-worth; the figure below categorises all of the traits being examined. When the PCL-R has been completed, the individual will have a score between 0 and 40 – 0 means they have no psychopathic tendencies or traits, whereas the latter means they are the paragon of a psychopathy. For each of the twenty psychopathic traits that the individual demonstrates, they are given a score between 0 and 2, depending on how greatly it is applicable to them. If the individual has a score greater than 30, this means they are a psychopath – and so qualify for a diagnosis, though the diagnosis would be of Antisocial Personality Disorder. (10,12)

Case Studies of Psychopathic Traits and Individuals

Hervey Cleckley, M.D., was an American psychiatrist and arguably the most influential historical figure in the field of psychopathy(13). Cleckley researched psychopathy throughout his academic career and compiled 15 case studies of prototypic psychopaths in his novel ‘The Mask of Sanity’ (14). One of the case studies in this novel is that of Tom, who is described by Cleckley as being an intelligent and healthy young man whose family were hoping for him to be diagnosed with some psychiatric disorder so that he would not serve jail time for his stealing. Cleckley describes how Tom would often skip school – suggestive of the psychopathic traits of a need for stimulation and irresponsibility – and that he would frequently steal from his family – embodying the psychopathic trait of criminal versatility. Furthermore, as a child, Tom often partook in delinquent behaviour, including shoplifting, setting fire to a privy in his local area, and throwing rocks at squirrels in the park – and again, these poor behavioural problems from an early age are also listed as psychopathic attributes in the Hare Psychopathy Checklist (Revised). When he became a teenager, Tom’s behaviour worsened, and he escalated from petty theft to car stealing and breaking into homes. Additionally, Tom was described as lying pathologically and doing so with sufficient charm to be convincing. For the next several years up to the age of 21 when Cleckley met him, Tom spent frequent spans of time in prison for stealing, initiating fights and various other instances of anti-social behaviour. The other fourteen case studies discussed in his novel detail people exhibiting very similar behaviour and characteristics. In analysis of these cases, Cleckley wrote “some of these patients I believe are definitely psychopaths but to a milder degree”. However, Cleckley also wrote that a person who engaged in anti-social behaviour was not definitively a psychopath, and through his research and analysis of psychopathy he worked to compile ideas about psychopaths as specific individuals – such as ‘the psychopath as a gentleman’ and ‘the psychopath as a scientist’. Overall,‘The Mask of Sanity’ formed the basis of what is now known as ‘psychopathy’, and led to considerable development in the study of this condition.

Another example of case studies of psychopathy can be found in the article ‘Incurable Psychopaths?’ by Marianne Kristiansson, MD (15). The first case detailed in this article is one of a 38-year-old man, who exhibited hyperactivity, restlessness and had engaged in criminal behaviour for many years – and had 13 convictions, including for assault. He had a history of drug and alcohol abuse and was admitted for a forensic psychiatric evaluation after he was suspected of assault again. This man was examined using the Hare Psychopathy Checklist Revised (PCL-R) and scored 36. This resulted in him being diagnosed with antisocial personality disorder and was thereafter treated with lithium. This treatment method appeared to stabilise him and led to a drop in his criminal behaviour and restlessness. Modern day treatments for antisocial personality disorder, however, often do not involve medication but rely on therapy – such as cognitive behaviour therapy – instead. 


In the modern world, the term ‘psychopath’ tends to be used more in the legal sense – often in cases of forensic psychiatric evaluations of criminals – than in the medical sense, and this is why psychopathy has a stigma of being equated to violent criminality. While the two are not mutually exclusive, psychopaths can lead relatively normal lives without anyone, including themself, being aware that they are a psychopath. Arguably it is difficult to achieve this though, as psychopaths often lack the ability to form long-term emotional connections – and as a fundamental basis of human nature this can complexify and isolate their lives. Further, the previous diagnosis of psychopathy as antisocial personality was solely based on the superficial traits listed in the PCL-R, modern research into the neurobiology of this condition can make diagnosis more accurate. Moreover, it shows how being a psychopath is an innate condition rather than singularly the product of the environment in which the individual is surrounded by – and especially that the prefrontal cortex is the region of the brain most closely linked with psychopathy to date. Despite this progress, the quote from Cleckley’s ‘Mask of Sanity’ still stands: “I do not believe that the cause of the psychopath’s disorder has yet been discovered and demonstrated. Until we have more and better evidence than is at present available, let us admit the incompleteness of our knowledge and modestly pursue our inquiry.” (14).

Samara Macrae, Youth Medical Journal 2022


1.   Psychiatric Times: “The Hidden Suffering of the Psychopath” –

2.   YouTube – MedCircle: “Narcissist, Psychopath, or Sociopath: How to Spot the Differences” –

3.   Science Direct: “Psychophysiology of Mental Health” by B.F. O’Donnell, W.P Hetrick –

4.   Journal of Young Investigators: “The Fear Factor: Fear Deficits in Psychopathy as an Index of Limbic Dysregulation” –

5.   Journal of the American Medical Association: “Localization of Deformations Within the Amygdala in Individuals With Psychopathy” –

6.   US National Library of Medicine: “The role of prefrontal cortex in psychopathy” –

7.   Smithsonian Magazine: “Phineas Gage: Neuroscience’s Most Famous Patient” –

8.   Mental Health America: “Psychopathy vs Sociopathy” –

9.   WDH: “Examples of antisocial behaviour”  –

10.   Encyclopaedia: “Hare Psychopathy Checklist” –

11.   Wikipedia: “Robert D. Hare” –

12.   The European Journal of Psychology Applied to Legal Context: “A contrastive analysis of the factorial structure of the PCL-R: Which model best fits the data?” –

13.   APA PsycNet: “Cleckley’s psychopaths: Revisited” –

14.   ‘The Mask of Sanity’ by Hervey Cleckley, M.D. (5th edition) –

15.   ‘ResearchGate: “Incurable Psychopaths?” by Marianne Kristiansson, MD –

By Samara Macrae

Samara MacRae is a student at Brighton College, England. She hopes to pursue medicine in the future, and is especially interested in surgery and emergency medicine.

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