There seem to be two kinds of pain: fundamental “sensory” pain, the intensity of which is a direct function of the intensity of various pain stimuli, and “psychological” pain, the intensity of which is highly modifiable by such factors as hypnotism, placebos, and the sociocultural setting in which the stimulus occurs.

Physiological, cognitive, and behavioral theories of pain each have their own view of the nature of the two kinds of pain. According to physiological theory and cognitive theory, “psychological” pain and “sensory” pain are both internal processes, with the former influencing the latter as central processes influence peripheral processes. According to behavioral theory, “sensory” pain is a reflex (a respondent) while “psychological” pain is an instrumental act (an operant). Behavioral theory claims that neither kind of pain is an internal process — that both are overt behaviors.

Although both physiological theory and cognitive theory agree with common sense that pain is internal, they disagree with commonsense intuitions at other points. They are no better at explaining the subjective experience of pain than is behavioral theory. They have not generated treatments for pain that are superior to those generated by behavioral theory. There is no basis for the frequent claim by antibehaviorist philosophers and psychologists that behaviorism, because it cannot explain pain, is less capable of explaining mental phenomena than physiology or cognition.