HOW do you react when you see somebody else in pain? Most of us can empathize with someone who has been injured or is sick - we can quite easily put ourselves "in their shoes" and understand, to some extent, what they are feeling. We can share their emotional experience, because observing their pain activates regions of the brain which are involved in processing the emotional aspects of pain.

But can seeing somebody else in pain actually cause pain in the observer? People with mirror-touch synaesthesia are known to experience touch sensations when they see others being touched, and this may also extend to pain in such individuals. There are also several anecdotal cases of patients who experience pain in the absence of noxious stimuli. And a new study by British psychologists now provides evidence that a significant minority of healthy people can also experience pain when seeing others' injuries.

Jody Osborn and Stuart Derbyshire of the University of Birmingham recruited 108 participants, and showed them static images (below) and film clips depicting painful events. The participants were asked to report anything they felt while viewing the images, and to rate the level of disgust, unpleasantness, sadness and fear elicited by each, using a questionnaire. They were also asked to report the level of empathy they felt for the person in each photograph.

Thirty one of the 108 participants, or about one third of the group, reported feeling pain in response to one or more of the images or clips. The sensations they felt were most often described as "tingling", followed by "aching". Other descriptions included "sharp", "shooting", "throbbing", "stabbing" and "tender". The pain was described as lasting for "a few seconds", "fleeting", or "for a split second as soon as the picture appeared." The black and white photograph of the athlete with a broken leg generated the most pain responses, and the highest pain intensity. In every case, the pain they felt was in the same location as that of the observed injury. For example, when they saw the image of the finger injury, they marked a cross on the finger of a diagram in the questionnaire.





Ten of these "pain responders" were then selected for a functional neuroimaging study, along with another ten non-responders, who acted as controls. The twenty participants then had their brains scanned whilst viewing the same images and film clips. These experiments confirmed the behavioural data - in the responder group, observing the images and film clips was correlated with strong activation of the so-called pain matrix, a diffuse network of brain areas which includes the anterior cingulate cortex, insula and prefrontal and somatosensory cortices. In the non-responders, those components of the matrix involved in emotional responses to pain (the cingulate and prefrontal cortices) were activated, but those which process sensory signals (the insula and somatosensory cortex) were not.

These experiments provide convincing evidence that a significant minority of otherwise healthy people experience not just the emotional component of pain, but also the sensory one, when they observe others in pain. When asked about the pain they experience when observing somebody else in pain, all thirty one responders spoke about it as if it was normal, and assumed that their experiences were representative of the population as a whole. Interestingly, no significant relationship was found between the reported levels of pain intensity and empathy, or feelings of disgust or unpleasantness. So although many will readily share the emotional perspective of someone seen to be in pain, and empathasize with them, this is in most cases unrelated to any sensory experience.



It is unclear why observing pain elicited pain in some participants but not others. The pain responders were found to have a stronger emotional response to the images and film clips of injuries, and this was associated with stronger activation of the pain matrix components involved in processing the emotional content of the stimuli. They also reported higher levels of empathy with the people depicted in the photos and films. It is therefore possible that this increased emotional response may drive a secondary reaction in the somatosensory areas. Conversely, the pain experienced by the responders may be dependent on a stronger somatic response, which drives a secondary emotional response.

Osborn and Derbyshire are now investigating whether responders can see things from others' perspective more readily than non-responders, and if they are more suggestible. Regardless of the underlying neural mechanisms or of individual differences, the knowledge that seeing others in pain can generate painful sensations in some observers may provide insights into the mechanisms of functional pain. It could also help researchers to gain a better understanding of conditions such as chronic pain and fibromyalgia, in which there is often no identifiable physical cause for the symptoms.



Related:

Osborn, J., & Derbyshire, S. (2009). Pain sensation evoked by observing injury in others. Pain. DOI: 10.1016/j.pain.2009.11.007.

