According to the International Association for the Study of Pain, pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” (“ IASP Terminology – IASP ,” 2017) Whether it results from stepping on a tack, falling down the stairs, or touching a hot stove, pain is the body’s way of saying “Stop doing that!”
Much as we may find pain unpleasant, it serves a vital role in survival. Although almost everybody experiences pain, a very few people are born with Hereditary Sensory and Autonomic Neuropathies types IV and V; these disorders result in an insensitivity to pain.(Auer-Grumbach, 2013) The results are instructive, if horrifying. While all infants put things in their mouths, babies with HSAN IV or V tend to bite their tongues and fingertips hard enough to cause significant damage. As they grow and explore their environments, they fearlessly fracture bones and damage joints without noticing, leading to hospitalisation or early death, and sometimes accusations of child abuse for the parents who cannot keep them safe. (van den Bosch et al., 2014)
Even pain that persists after the original injury seems to be evolutionarily advantageous. A study of squid for whom persistent after-injury pain was prevented found them just as appealing to predators as similarly injured squid who experienced ongoing pain. Six hours after injury, researchers observed no differences in the three groups’ swimming abilities, but black sea bass pursued both injured groups longer and farther than they pursued the healthy controls. Squid who experienced ongoing pain from the injury were aware of the presence of the fish earlier and began defensive manoeuvres before either uninjured or pain-free injured squid. Pain-experiencing squid were three times as likely to survive 30 minutes in a tank with the black sea bass than injured but pain-free squid. This is a significant difference; despite their advantage of less-persistent pursuit, healthy squid were less than twice as likely to survive the trial than the injured squid who experienced ongoing pain. (Crook, Dickson, Hanlon, & Walters, 2014)
Unpleasant though it may be, then, the ability to experience and respond to pain is important to survival and long-term well-being.