Observer judgments of acute pain: facial action determinants.

We provided a microanalytic description of facial reactions to a series of painful and nonpainful electric shocks and examined the impact of these as discrete facial cues for observer judgments of acute pain. Thirty female volunteers were videotaped and reported their discomfort in response to electric shocks after earlier exposure to one of three social influence conditions: a tolerant model, an intolerant model, or neutral peer presence. We coded the videotapes for facial activity using the Facial Action Coding System (Ekman & Friesen, 1978b), and peer judges rated them for painful discomfort. Subjects exposed to a tolerant model reported no more discomfort than did subjects exposed to an intolerant model, despite receiving more intense levels of shock, but were judged by observers to be in more pain. Analyses of facial activity yielded consistent findings: Tolerant-model subjects, though reporting discomfort equivalent to that reported in other groups, displayed more pain-related facial activity (brow lowering, narrowing of the eye aperture from below, raising the upper lip, and blinking). There was a substantial direct relation between observer judgments of distress and discrete, pain-related facial actions (mean multiple R = .74 for the various shock levels rated). These data indicate that nonverbal expression yields information about the response to noxious stimulation that is non-redundant with self-report.