July 31, 2018
Written by: Nitsan Goldstein
Chances are if you’ve ever watched USA Network on a Saturday afternoon, you know what a psychopath is. While psychopaths are quite rare in the general population, crime show after crime show takes advantage of our fascination with these often incredibly intelligent, socially competent people who turn out to be manipulative cold-blooded killers. Psychopathy is a personality disorder characterized by impaired empathy and remorse, and bold, disinhibited, and egotistical traits. Psychopaths mainly exhibit self-serving behaviors with no regard for others, and while some are able to use these traits to achieve success, many end up committing violent crimes and are eventually incarcerated. But what do we know about the underlying biological basis of psychopathy, and how can looking into the brains of killers better inform intervention strategies to prevent violent crime?
Where is empathy in the brain… and do psychopaths have it?
If you’re watching a sporting event and a player gets badly injured, the natural response of most people is to look away. It’s unpleasant to watch someone in pain. The reason for this is that some of the same areas of the brain that are active when we are in pain also activate when others are in pain, in some ways allowing us to feel their pain. This phenomenon is called empathy, and it’s very important in our society. Empathy can be a powerful force that prevents us from harming others to advance our own needs, something that psychopaths often do. Therefore, neuroscientists are very interested in what these regions are that are active both when we’re in pain as well as when we see others in pain, and how these regions might act differently in psychopaths. In order to study the activity in different areas of the brain while subjects are viewing images or performing a task, neuroscientists use functional magnetic resonance imaging (fMRI). fMRI measures changes in blood flow to different regions of the brain, which is thought to correlate with the level of activity in that region. By scanning many healthy controls, researchers can get an idea of what brain areas are consistently activated by different stimuli and start to make hypotheses about how these regions might be involved in a coordinated network.
When non-criminal control subjects are shown pictures of painful events such as a finger stuck in a door, activity in a subset of brain regions that together make up the brain’s limbic system including the anterior insula (aINS), anterior cingulate cortex (ACC) and the amygdala, consistently increases (to see where the ACC is located in the brain, see Figure 1).
This pattern of activity occurs when the subjects are asked to imagine the events are occurring to them or to others. When incarcerated psychopaths are scanned, however, activation of these areas only occurs when they imagine the painful scenarios are occurring to themselves, but not to others. Remarkably, the higher the individual scored on scales of psychopathic traits, the lower the activity in their amygdala and insular cortex when imagining others in pain1. This suggests that it is not a global dysfunction in the response to pain, but a failure of the same network that activates when they themselves feel pain to activate when others feel pain. It is therefore possible that the altered activation pattern observed in this network underlies the lack of emotional empathy that is central to psychopathy and antisocial behavior.
Bad decisions, or faulty wiring?
A lack of empathy on its own does not land someone in prison. Incarcerated violent criminals are in prison because at some point they made a decision to commit a crime. The neuroscience of decision making is an active field that also takes advantage of fMRI to study what brain regions are involved in making decisions. One group used fMRI to ask whether decision making processes are altered in psychopaths, and how differences in activity patterns in their brains could explain these alterations. They scanned the brains of incarcerated psychopaths and controls while participants performed a decision-making task that requires them to choose between receiving a small monetary reward now, or a larger reward later. They found that individuals with high scores on psychopathy scales had increased activity in the nucleus accumbens (NAc) in response to the immediate reward compared to controls. The NAc is a region classically believed to be involved in reward signaling, with activity increasing in response to rewarding stimuli. Psychopaths, therefore, experienced heightened reward signaling in response to the smaller but immediate monetary reward. They also found decreased connectivity between the NAc and the ventromedial prefrontal cortex (vmPFC). It is thought that the vmPFC dampens the response in the NAc to guide decision making, suggesting that this reduced connectivity may be the cause of the heightened sense of reward experienced by the psychopathic subjects. The researchers hypothesize that the reduced connectivity of these two regions may make it more difficult for psychopaths to incorporate information about the long-term consequences of their actions into their decisions to commit crimes. In fact, the scientists were able to accurately predict the number of times subjects had been convicted of crimes using only the measure of connectivity between the NAc and the vmPFC2.
When critical associations break down
It is estimated that psychopaths make up 70% of repeat violent offenders3. This suggests that psychopaths not only commit crimes, but they often commit more than one. One factor that may contribute to repeat offending is the inability to properly make associations between their crime and the consequences that followed. The ability to make associations is critical to our daily lives. Have you ever been sick after eating bad fish, for example, and the smell of fish makes you nauseous for months, if not years? If so, you’ll recognize how we associate the unpleasant feeling (sickness) with the previously neutral stimulus (smell of fish) and preemptively respond to the stimulus (nausea). This ability, called classical conditioning, is extremely advantageous and observed throughout the animal kingdom. It turns out that psychopaths have diminished fear conditioning, a type of classical conditioning where the unpleasant feeling is fear. Several studies have shown that activity in brain regions involved in fear conditioning (the limbic-prefrontal circuit, which includes many of the same areas involved in empathy) is impaired in psychopathic individuals4,5. Many of these studies pair pictures of neutral faces with an unpleasant prick. In control, but not psychopathic subjects, the limbic-prefrontal circuit activates in response to the previously neutral face once it’s been associated with the prick. Interestingly, the autonomic nervous system of psychopaths is impaired as well. Researchers found that in control participants, skin conductance (an indirect measure of arousal) increases at the presentation of the faces once they’ve been associated with the prick. In psychopaths, however, arousal does not increase at the presentation of these faces, even after they’ve made the association. These studies highlight another way in which psychopaths are unable to experience negative emotions at times where they are appropriate.
So what can we do?
Violent crime is both a major public health concern as well as a massive financial burden in the United States. A team at Iowa State University estimated that a single murder costs society a whopping $17.25 million6. How can research on the neuroscience of psychopathy help reduce its toll on society? Research into the biological basis of psychopathic traits can help with early identification of individuals predisposed to violence. Many psychopaths begin to exhibit antisocial behaviors as children, and interventions aimed at preventing violence rather than treating it are obviously attractive. Neuroscientists also hope that by understanding the underlying network dysfunction of psychopathy, therapies can better target the initiating factors of violent crime, such as the inability to weigh long-term consequences into decision-making. Hopefully as imaging techniques continue to improve and our knowledge of the brain areas involved in empathy, decision-making, and fear conditioning expands, we can further improve interventions and treatment of psychopathy and violent crime.
- Decety, J., Chen, C., Harenski, C. & Kiehl, K. An fMRI study of affective perspective taking in individuals with psychopathy: imagining another in pain does not evoke empathy. Frontiers in Human Neuroscience 7, 489 (2013).
- Hosking, J. G. et al. Disrupted Prefrontal Regulation of Striatal Subjective Value Signals in Psychopathy. Neuron 95, 221–231.e4 (2017).
- Egan, D. “Into the Mind of a Psychopath.” Discover Magazine. 4 May 2016. Discovermagazine.com/2016/June/12-psychopathy-and-the-hare.
- Rothemund, Y. et al. Fear conditioning in psychopaths: Event-related potentials and peripheral measures. Psychol. 90, 50–59 (2012).
- Birbaumer, N., Veit, R., Lotze, M. & al, et. Deficient fear conditioning in psychopathy: A functional magnetic resonance imaging study. Gen. Psychiatry 62, 799–805 (2005).
- Iowa State University News Service. 27 Septempber 2010.https://www.news.iastate.edu/news/2010/sep/costofcrime.
Cover image from Wikimedia Commons, Creative Commons CC0 1.0 Universal Public Domain, commons.wikimedia.org/wiki/File:MRI_Location_Amygdala_up.png
Figure 1 from Wikimedia Commons, public domain, commons.wikimedia.org/wiki/File:Gray727_anterior_cingulate_cortex.png