Scientists have spent 20 years using magnetic resonance imaging (MRI) to ask a question that is of great interest to the public, the focus of countless podcasts, TV shows, movies, and conversations around the kitchen table: what is going on inside a psychopathic person’s brain? Or, more scientifically, what are the neural correlates of psychopathy?
This question is hotly discussed because psychopathic people have a detrimental impact on society. They commit a large share of crime, and they’re more likely than most other people to continue committing crimes after suffering legal consequences. Most studies of the brain basis of psychopathy have been aimed at identifying potential targets for treatment for this costly disorder.
We gathered all existing MRI studies of psychopathy and conducted a meta-analysis to find the brain regions that are commonly linked to psychopathy across studies. These regions may show consistently greater activity or consistently less activity compared to people who are relatively healthy.
We found that psychopathic people tended to show more activity (in red above) in several regions. This included the dorsomedial prefrontal cortex, posterior cingulate cortex, and the amygdala.
If you’re familiar with theories about the brain basis of psychopathy, that last one might be surprising to you. Influential theories in the field hypothesize that psychopathy is related to lower activity in the amygdala, the so-called ‘fear center’ of the brain. (Side note: there probably is not a ‘fear center’ in the brain.) But we found more activity in the amygdala (on the far right above).
But what I found even more interesting is that each of these regions (including the amygdala) fall within the default mode network (in light blue below). This is a large-scale network that seems to be important for focusing attention internally, for example mind-wandering or thinking about yourself. This network tends to decrease its activity when a person starts to focus on external things, like doing an experimental task on a screen. When relatively healthy people perform experimental tasks, they often make more mistakes in instances when default mode network activity fails to decrease. Psychopathic people showed more activity in this network when doing a variety of experimental tasks, which could be thought of as a failure to decrease activity in this network.
Interestingly, prior studies have shown that psychopathic people make more mistakes on mundane experimental tasks. They also direct their attention differently from relatively healthy people. So, just to make a wild guess, it’s possible that increased default mode network activity is related to differences in how psychopathic people are directing their attention during experimental tasks.
The only region in which psychopathic people tended to show less activity was the anterior cingulate cortex (in blue at the top of the page). This region is a key part of what’s often called the salience network, which plays a vital role in extracting new and important information from the body and from the environment. The salience network is also involved in switching from default mode network activity to an externally-oriented attention network. So, to make another wild guess, it’s possible that, when psychopathic people encounter new and important information, their anterior cingulate cortex fails to pick up that information, and then fails to send a signal to default mode network regions telling them to decrease activity. To me, this is a very intriguing possible explanation for the dramatically different way in which psychopathic people interface with the world.
Of course, we will need to test these hypotheses in future studies.
I will also make an important public service announcement here: Even though we were able to identify brain regions that tend to function differently across studies, at this time we are still unable to diagnose psychopathy from a brain scan.
I repeat: We cannot diagnose psychopathy from a brain scan.
We have plenty of good interviews and questionnaires that we use for diagnosing psychopathy. But we have not identified a pattern of brain activity that always (or almost always) indicates a person has psychopathy. Maybe we will identify a diagnostic pattern of brain activity in the future, or maybe we never will. But we do not have one right now.
Read the paper here.
Deming, P. & Koenigs, M. (2020). Functional neural correlates of psychopathy: A meta-analysis of MRI data. Translational Psychiatry, 10(133), 1-8.