There is a neurobiological basis for a lack of guilt and empathy in psychopathy – but it depends on the type.
Written By: Michèle Bachmann
Art By: Yang Xin
A ruthless businessman, con artist, serial killer – in popular media and public perception, the psychopath plays a multitude of roles. While an increasing number of narratives including cold, emotionless and violent criminals have been flashing across TV and cinema screens, the scientific community has placed its focus on a fundamental exploration of the disorder. Psychopathy remains one of the mysteries of psychology, personality and, as recent studies indicate, of neurobiology as well. The first approaches dedicated attention to the personality facets of psychopathy and provided basic knowledge about psychopaths. Two factors were found: Factor 1 as defined by the PCL-R (Psychopathy Checklist – Revised) includes glibness and manipulative, egocentric behaviour, a lack of guilt and empathy and diminished emotions. Factor 2 describes antisocial and impulsive behaviour, a lack of responsibility, problems with behavioural inhibition and risky or excitement-seeking actions. However, it was soon recognized that an understanding of psychopathy would be impossible to achieve if only behaviour and personality were considered. What role do biological and physiological factors play in the development and expression of psychopathy?
Although some promising research on neurobiological changes in psychopathy has emerged, the true etiology remains unclear. Based on studies that investigated psychopathy-resembling changes in behaviour after brain injuries, it was hypothesized that maldevelopment in the same areas could be a key factor in the etiology of psychopathy. A study in 2010 compared the level of development in the septum pellucidum for participants that were also evaluated on criminal convictions and psychopathy. The septum pellucidum is a membrane that grows to close up the space between the two lateral ventricles, which are caverns in the brain filled with cerebrospinal fluid. The fluid serves important functions in maintaining the brain’s cushioning against injuries as well as chemical homeostasis. An only partially closed septum pellucidum, where a ‘cave’ remains between the ventricles, indicates abnormal fetal development. In the study, participants with a cave had higher scores on a psychopathy scale as well as more criminal convictions. However, it cannot be concluded that the cave is the cause of psychopathy; it may simply be one of many neurodevelopmental markers indicating that an abnormal form of development has occurred.
Another area of the brain often related to psychopathy is the prefrontal cortex. As proven by famous cases of brain injury such as Phineas Gage, this lobe was shown to be involved in executive functions such as planning, monitoring and evaluating of actions, important goal-directed behaviour, processing of social and emotional signals and complex behaviour such as responsibility and abstract thinking. Due to similarities between the conditions, studies on antisocial individuals are often considered for research on psychopathy and point towards lower performance of the prefrontal cortex as well as less structural connectivity. Studies on the prefrontal cortex have found diminished blood flow for psychopaths lacking emotion and an ability to feel guilt. Interestingly, other research revealed increased volume and functional connectivity of the prefrontal cortex in psychopaths – but only in those that were more antisocial and impulsive than they were emotionally cold and lacking in guilt. Thus, higher expression of factor 1 of the PCL-R seems to be associated with lower prefrontal volume, while psychopaths higher in factor 2 display more prefrontal volume. This further highlights differences between two types of psychopaths – those showing lack of guilt and emotion from a young age onward, traits often related to genetically determined neurobiological changes, and those with a more antisocial profile that scientific studies find to have been influenced by adverse environmental conditions and social problems.
Similar observations were made in experiments involving the amygdala, an almond-shaped structure known to be involved in emotional processing. Studies showed decreased volume and higher asymmetry between both amygdalae in psychopaths compared to healthy controls. Also, the surface of psychopaths’ amygdalae showing deformations correlated with a lack of emotion (factor 1). Neuroimaging techniques pointed towards less activation of the amygdalae of psychopaths when faced with fear, moral judgment and pain in others; however, pain inflicted on the individual activated the amygdala similar to control groups. This indicates a neurobiological basis for a lack of guilt and empathy in psychopathy. Psychopathic participants also performed worse on gambling tasks involving risk and loss; these tasks are commonly associated with impairments in the function of prefrontal cortex and amygdala.
Different theories have been proposed to explain this neurobiological etiology of psychopathy as well as the variation of psychopathy into two types. Blair, a leading researcher in the field, refers to reactive aggression as being present in the antisocial type, so-called ‘acquired sociopathy’, due to the brain’s inability to associate the individual’s actions with the consequences, specifically in relation to fear and pain in other people. Lower physiological and emotional reactivity stems from this lack of communication between brain structures. The second type is described as using proactive, goal-oriented aggression without guilt, as a maldevelopment of brain areas early in life impairs their ability to process others’ emotions properly.
Up until now, there have not been enough studies to draw final conclusions about the connection between neurodevelopmental changes and psychopathy. But current research indicates that this drastic change of personality could be rooted in a combination of genetics, fetal development and early childhood experiences. So maybe there is more to the psychopath on TV than a homogenous disorder with a single etiology, with future research hopefully indicating what exactly causes such a startling change of personality.