Pain judgements of patients' relatives: examining the use of social contract theory as theoretical framework.

Observer underestimation of others' pain was studied using a concept from evolutionary psychology: a cheater detection mechanism from social contract theory, applied to relatives and friends of chronic pain patients. 127 participants estimated characters' pain intensity and fairness of behaviour after reading four vignettes describing characters suffering from pain. Four cues were systematically varied: the character continuing or stopping liked tasks; continuing or stopping disliked tasks; availability of medical evidence; and pain intensity as rated by characters. Results revealed that pain intensity and the two behavioural variables had an effect on pain estimates: high pain self-reports and stopping all tasks led to high pain estimates; pain was estimated to be lowest when characters stopped disliked but continued with liked tasks. This combination was also rated least fair. Results support the use of social contract theory as a theoretical framework to explore pain judgements.