The Cannon-Bard theory of emotion, proposed by Walter Cannon and Philip Bard, challenges the notion that emotions are solely the result of physiological responses. Instead, this theory suggests that emotional experiences and physiological arousal occur simultaneously but operate through independent mechanisms. This dual response is initiated by the brain, specifically by the thalamus, which plays a critical role in processing sensory information.

Upon perceiving a stimulus, such as a dangerous situation involving a venomous snake, the thalamus transmits sensory signals to both the cortex and the autonomic nervous system concurrently. The cortex is responsible for producing the conscious emotional experience, such as fear. At the same time, the autonomic nervous system triggers physiological responses typical of a fight-or-flight reaction, including an increased heart rate, rapid breathing, and the release of adrenaline. These responses are not caused by each other but rather occur together, illustrating the independence of emotional and physiological processes.

A key aspect of the Cannon-Bard theory is that it opposes the earlier James-Lange theory, which posits that emotions arise from physiological responses. Instead, the Cannon-Bard theory emphasizes that emotional experience, such as fear, and physiological arousal, like sweating or a racing heart, are parallel and independent. The autonomic nervous system activates physical responses, while the cortex generates the subjective feeling of the emotion. Both processes happen concurrently, providing a comprehensive explanation of how humans experience and react to emotions in real time.