Research examining social influences on pain has largely neglected the impact of friends, while studies on the social context of emotional display have demonstrated differences in expressivity in the presence of friends versus strangers. Given that pain is a universal phenomenon with both affective and sensory components, it appeared important to merge and extend research in both pain and emotions domains by examining the role of friends as determinants of pain experience and expression. An experimental investigation was undertaken to examine the impact of friendship, as a feature of audience effects and social modeling, on pain expression, as well as to examine the impact of menstrual factors that have been hypothesized to contribute to young women's current pain experience. Participants were female undergraduate students from the University of British Columbia. They were randomly assigned to undergo the cold pressor task with either a friend or a stranger, resulting in 52 pairs of friends and 52 pairs of strangers. Half of the participants had been exposed to the friend or stranger undertaking the task in advance of their own exposure to the cold pressor, so as to examine social modeling phenomenon. Measures of pain expression included self-rated pain intensity and unpleasantness, behavioural tolerance time, and facial pain activity. Robust social modeling effects were observed in all measures of pain, with the bulk of the modeling effect being expression modality-specific. A differential social modeling effect of friends vs. strangers was observed only in pain facial activity. Women's dysmenorrhea status and its severity, when evident, were unrelated to current pain expression. The presence of friends significantly facilitated expression of disgust but no significant group differences were observed for other emotions. Results are discussed from social communication model of pain and evolutionary perspectives and highlight individuals' apparent innate propensity to evaluate the costs and benefits associated with social communication. Future research is needed to elucidate factors that influence the transmission and reception of social information. / Arts, Faculty of / Psychology, Department of / Graduate