Pain is a virtually universal experience, yet understanding another person's pain poses great challenges. Because pain is subjective, much of what can be determined about a person's pain is based on what the individual verbally or nonverbally communicates. Therefore, it is useful to consider the task of pain assessment from a communications perspective; the individual attempting to understand another's pain is an observer who only has access to the sufferer's expression of pain. Facial expressions can be used as clues to understanding pain but they are subject to many influences. Social...