Answer: The James-Lange theory was an early theory to explain how the body experiences emotion.
William James and Carl Lange, two early psychologists in the mid 1880’s were searching for a basis for the origin of emotion. Prior to their theory, the generally accepted thought was that after experiencing some outside stimulus, the mind senses the emotion, and this emotion is responsible for eliciting a physiological response from the body and the organs. For example, if you were in the walking in a dark alley, and you saw someone running towards you with a knife, you would experience a physiological fear response: your heart rate might increase to improve blood flow to the muscles, and your breathing rate would increase to prepare for fight or flight.
The James-Lange theory, developed by the two independent of each other, flips the order of the processes. James and Lange believed that after presentation of a stimulus, the body and organs react automatically, and because of the physiological change, the mind then detects these changes and creates the emotion. The James-Lange theory suggests that emotions are a response to changes in physiology. According to the James-Lange frame of thought, if you were in the alley described above, the body would naturally increase heart rate and breathing in response to the stimulus, and these changes would send a signal to the brain that causes fear.
Walter Cannon and Philip Bard in the 1920’s developed a theory that is contrary to the James-Lange theory. According to the Cannon-Bard theory, the stimulus provokes an emotional change and physiological change simultaneously. In the Cannon-Bard theory, the thalamus is the main driver of both the physiological and emotional changes.
One major assumption of the James-Lange theory is that the bodily organs communicate with the brain to make emotions. A point against the body-first-then-brain argument is that emotional responses are still intact in people who are paralyzed completely from the neck down.
Today, the most widely accepted theory of emotion and physiology is that the Papez circuit, a series of brain regions, influences the physiology.