Pain: behavioural expression and response in an evolutionary framework

Abstract An evolutionary perspective offers insights into the major public health problem of chronic (persistent) pain; behaviours associated with it perpetuate both pain and disability. Pain is motivating, a need state, and pain-related behaviours promote recovery by: immediate active or passive defence; subsequent protection of wounds; suppression of competing responses; energy conservation; vigilance to threat; and learned avoidance of associated cues. When these persist beyond healing, as in chronic pain, they are disabling. In mammals, facial and bodily expression of pain is visible and identified by others as such. However, pain itself is modulated by social context, and conspecifics’ responses can result in pain reduction. The study of responses to pain has emphasized onlooker empathy, but observers frequently discount others’ pain; people with chronic pain report feeling disbelieved and stigmatized. This can be understood in terms of cheater detection on the part of observers – alertness to free riders that underpins the capacity for prosocial behaviours. These dynamics occur both in everyday life and in clinical encounters, and provide an account of the adaptiveness of pain-related behaviours.