For patients presenting with pain, a correct diagnosis and the development of the most appropriate treatment plan depend on a thorough and systematic evaluation of their suffering. Pain is not necessarily pathogenic because it can sometimes act as a defense mechanism. To be alert to and able to respond to harm, our species adapted mechanisms that allow us to feel and react to pain. Pain, however, is not necessarily associated with damaged tissues and may continue long after the standard healing period has passed. Pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage,” according to the International Association for the Study of Pain. Physical testing and other outside observers may not be able to capture the full range of a person’s subjective and individual perceptions of pain. The reliability of self-report measures of pain is high. There has been a lot of work in human pain research on assessing and bettering self-report methods.