The James-Lange theory of emotion, proposed by William James and Carl Lange in the late 19th century, asserts that emotions are the result of physiological reactions to external stimuli. Contrary to the traditional view, which suggests that emotions directly arise from the perception of stimuli, this theory proposes that emotions occur as a consequence of the body's responses to such stimuli. According to this framework, an emotional experience is a cognitive interpretation of physiological changes rather than a direct result of the stimulus itself.

When an individual encounters a threatening stimulus, such as a charging bull, the body undergoes a series of physiological responses. These responses might include an accelerated heart rate, rapid breathing, sweating, and muscle tension. The brain subsequently interprets these physiological changes and labels them as a specific emotion — in this case, fear. For instance, the theory would suggest that a person does not run because they feel fear; rather, they feel fear because they have started running and noticed their body's responses. This idea challenges the traditional notion that emotional experiences drive physical reactions.

Examples from everyday life further illustrate the James-Lange theory. Consider a person giving a public speech. Their heart may start to pound, their palms may sweat, and their voice may tremble. According to the James-Lange theory, the emotion of anxiety or nervousness arises because of these physiological reactions, not because of the act of public speaking itself. Another example is experiencing joy when laughing. It is not the joy that causes laughter; rather, the act of laughing and the associated physiological responses — such as a release of endorphins — are interpreted by the brain as the feeling of joy. As a result, the James-Lange theory provides a compelling framework for understanding the intricate connection between bodily states and emotional experiences.