My Pain is Your Pain

"If you feel pain, you're alive.

If you feel other people's pain, you're a human being,"    

Leo Tolstoy

Despite Tolstoy's proclamation of human exclusivity, all mammals feel others' pain. In fact, rodents are more distressed by witnessing other rats receive a painful electric shock than they are by receiving the same painful stimulus themselves. We animals dislike pain; it is, by definition, a salient, aversive, sensation which motivates avoidance, but more to the point, we animals also dislike witnessing others in pain. Distress and pain are contagious between all vertebrates. We wince if someone else stubs their toe; turn our eyes away from those writhing in agony. We can even vomit or faint at the sight of painful violence to others.

As a child, Fiona Torrance remembers watching a butcherbird pick up a mouse by the neck and hang it on a barbed wire fence by its skin. As she watched, she felt the pull of skin and muscle in her own neck and the drag on her spine as if she were being lifted. Naturally, she assumed everyone felt what they saw but, by the time she was in her early twenties, she realised perhaps she was unusual. Years later, on holiday in the U.S., she was sitting in the car waiting for her boyfriend to return from an errand when her attention shifted to two men shouting at each other on the other side of the road. As their altercation escalated, one of them punched the other so hard he fell unconscious to the ground. As she watched, Fiona also fell unconscious.

When her boyfriend returned, he insisted on taking her to hospital, despite her protestations that this was normal for her. Local medics did not know what was wrong with her and so assumed she must have had a seizure. Back in the UK, after months of tests, neuroscientists diagnosed an extreme form of pain contagion in which she feels in her own body everything she witnesses happening to someone else. We know people like Fiona genuinely experience pain because brain imaging techniques reveal heightened activity in the somatosensory cortex (the region dealing with felt sensation). 

Most of us have a more subdued response to witnessing physical injury—but pain contagion is ubiquitous. In one study, a large group of 'normal' volunteers looked at photographs of an athlete breaking his leg. About one third felt pain in their own leg; the other two-thirds did not feel pain but found the image aversive. Those who felt pain contagion could describe stabbing, shooting, sharp and tingling sensations, and scans confirmed activity in their brain's pain matrix. They were feeling the discomfort illustrated in the photograph as their own [1].

One reason we (and other vertebrates) don't enjoy witnessing or hearing cries of pain or indeed even thinking about pain in others is that it activates pain regions in our own brain as if we are experiencing it firsthand. Brain imaging studies show that the same neural circuit is involved in the experience of physical pain and even the imagination of pain in another individual [2]. Merely hearing sounds of distress or being told that someone is hurt are enough to elicit pain contagion. In one rather unkind experiment, they showed groups of women a hand and an arrow on a computer screen; if the arrow pointed to the hand, it meant that their husband (in another room) had received a painful electric shock to their hand. If the arrow pointed away from the hand, it meant he had not received a shock. Those wives who thought their husband had been hurt, showed a brain response as if they had received an electric shock to their own hand. Those wives who thought their husband had not been shocked showed no such brain activity. These women saw no visual images of pain, nor did they hear any yelps; they merely thought that their husband had been hurt (in fact, no husbands were hurt during this experiment).

Pain contagion is highly specific. If we see pictures of a person trapping a finger in a door, our brain activates in regions that code for pain in that same specific finger on our own hand. There is also an element of 'intensity coding' taking place as the severity of injury which we witness influences how much vicarious pain we also experience.

Neuroscientists have uncovered a two-tier system of 'pain empathy' kicking in when we witness pain: first, an immediate low-level activation of a defensive system and feeling the pain via a low-level automatic reflex in the spinal cord—a self-protection response of aversion occurring about 160ms after the event. Then, there is a second response, at about 380ms, a higher-level assessment of what to do about it, including moving forward to approach or actively help the other. This can produce conflict when witnessing others' pain because we can feel both an automatic response to run away and another to rush forward to help [3].

Our responses depend on the relationship we have with the one being pained. We feel the pain of others unless we have fallen out with them when, shame to say, our pleasure centres fire up. More fascinating still, is the difference between genders. Males show far less pain contagion after a disagreement with other males and primatologist, Frans De Waal, wonders whether this reflects an evolutionary advantage to avoid feeling empathy for potential rivals. It would certainly be a disadvantage when competing for resources or territory to feel your opponent's pain.

We feel less pain contagion when we are watching movement. Why would this be? It comes from the need to embody what we are seeing in order to understand it. As we watch movement we simulate the movement in our own body as part of how we understand what is going on. The same is true of pain contagion. We feel others pain by simulating how it would feel in our own body. When we are watching movement, we cannot also simulate pain and so pain contagion is reduced.

What these and other studies show is that sharing someone else's pain is neither an automatic reflex nor a mirror reflection of what we are seeing, but a sophisticated assessment of what is going on for someone else.

More exploration of somatic empathy in my new book ANOTHER SELF (UK book, US book)

[1]       J. Osborn and S. W. G. Derbyshire, "Pain sensation evoked by observing injury in others," Pain, vol. 148, no. 2, pp. 268–274, 2010.

[2]       J. Decety and L. Skelly, "The Neural Underpinnings of the Experience of Empathy: Lessons for," in … of Cognitive Neuroscience, The …, vol. 2, no. June, 2013, pp. 1–19.

[3]       I. Riečanský and C. Lamm, "The Role of Sensorimotor Processes in Pain Empathy," Brain Topography. 2019.

The wonderful illustration cover image is by Aarón Blanco Tejedor

@innernature c/o Unsplash