Psychopaths experience pain differently, even when their bodies say otherwise

Psychopathy has long been associated with murderers, notorious criminals, and the griping true crime stories that dominate Netflix documentaries. But our recent research is showing they have a complex relationship with pain which may in part be responsible for their lack of empathy.

Psychopathic traits are on a spectrum. We all have levels somewhere on this scale. To be deemed a “psychopath” by some medical professionals, though, you would need to sit on the higher end of the spectrum.

Typically, people who are higher on the psychopathic traits spectrum show greater pain tolerance. And this is usually reflected in their physiology. For instance, in a 2022 study people higher in psychopathic traits showed lower brain activity with pressure pain.

When we conducted our recent research on pain and people with different levels of psychopathy, our results surprised us. Participants with high levels of psychopathy seemed to process pain differently to people low in psychopathy.

We applied pressure pain to our participants using a device that gently pressed a small circular probe onto the participant’s fingernail using compressed air. We measured their reactions from their sweat responses.

This is called skin conductance response (SCR), and is activated in times of “fight or flight”, or even when we need to pay attention. And this normally increases sweat production. That’s what we used to measure participants’ response to pain and empathy in our experiment.

Before our experiment began, we slowly increased the levels of pressure that participants felt until they told us they had reached their pain threshold (the most pain they could bear). The low and high psychopathy groups chose similar levels of pressure for their pain threshold.

Next, we delivered varying levels of pressure (with the highest being each participant’s pain threshold) to ensure participants did not become used to the stimulations. Following each stimulation, participants were asked to rate how much pain they felt using a self-report measure ranging from 0-100.

We found that participants higher in psychopathy reported feeling less pain than participants who were lower in psychopathy. The high psychopathy group even rated their own pain thresholds as less painful than the low psychopathy group (on the 0-100 scale). However, their SCRs were the same as those lower in psychopathy.

So, what does this mean?

It suggests that people higher in psychopathy interpret pain differently. Perhaps this explains why psychopathy relates to greater risk-taking and increased levels of violence or aggression towards others – they do not recognise feelings of pain in the same way as other people.

Usually, psychopathy relates to lower levels of physiological responses in threatening situations because they don’t associate pain with fear or punishment.

The results of our study suggest that the difference in pain perception between high and low psychopathic people may be psychological rather than physiological. This could explain why there were differences in self-reports, but not in sweat responses.

We don’t know whether they are pretending to feel pain or are less connected to their body’s physiology. But a 2019 study on children suggests those high in psychopathic traits may engage in extreme coping when scared. For instance, those children showed blunted emotional responses, disengagement or risky behaviour to cope with the stress.

What about empathy for other people’s pain?

We also tested our participants’ responses to other people’s pain by showing them images, such as a hand trapped in a door or a bare foot stepping on glass. Previous research has shown that people higher in psychopathy show reduced levels of physiological arousal to other people’s distress.

For example, a 2015 study found people higher in psychopathy demonstrated lower levels of brain activity when seeing other people in painful situations. In our study, we found that people higher in psychopathy not only reported feeling less empathy but also showed lower sweat responses when viewing other people’s pain.

This lower SCR has also been found in male prisoners with psychopathic traits. And it typically indicates less attention or focus on other people’s pain.

Our study shows that a lack of empathy for others may not be a conscious choice. Our recent systematic review, where we looked at eight previous studies on psychopathy and pain perception, also helped to corroborate these findings, showing that psychopathy links to lower levels of brain activity in response to other people’s pain.

Research has shown that lower levels of empathy for other people can be influenced by a higher tolerance for pain. If someone does not understand the feelings of pain the same way as other people, they probably don’t understand the pain that other people may be experiencing.

Also, a 2020 review showed that the brain networks used in processing pain are also used to process empathy. This could mean that if people higher in psychopathy don’t feel as much pain themselves, their perceptions of other people’s pain could also be reduced via this shared network.

Just because you show higher psychopathic traits does not necessarily mean you are going to be the lead character of your own true crime documentary, though. In fact, recent research, including a 2022 study, noted psychopathic traits can be positive and help people regulate their emotions.

Surgeons and other medical professionals show high levels of psychopathic traits, particularly the stress immunity part of the personality trait.

Perhaps this is what allows medical professionals high in psychopathic traits to stay calm under pressure, allowing them to make quick, rational decisions without being overwhelmed by stress.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.