Emotion is a complex, subjective experience accompanied by biological and behavioral changes. Emotion involves feeling, thinking, activation of the nervous system, physiological changes, and behavioral changes such as facial expressions.
Different theories exist regarding how and why people experience emotion. These include evolutionary theories, the James-Lange theory, the Cannon-Bard theory, Schacter and Singer’s two-factor theory, and cognitive appraisal.
More than a century ago, in the 1870s, Charles Darwin proposed that emotions evolved because they had adaptive value. For example, fear evolved because it helped people to act in ways that enhanced their chances of survival. Darwin believed that facial expressions of emotion are innate (hard-wired). He pointed out that facial expressions allow people to quickly judge someone’s hostility or friendliness and to communicate intentions to others.
Recent evolutionary theories of emotion also consider emotions to be innate responses to stimuli. Evolutionary theorists tend to downplay the influence of thought and learning on emotion, although they acknowledge that both can have an effect. Evolutionary theorists believe that all human cultures share several primary emotions, including happiness, contempt, surprise, disgust, anger, fear, and sadness. They believe that all other emotions result from blends and different intensities of these primary emotions. For example, terror is a more intense form of the primary emotion of fear.
In the 1880s, two theorists, psychologist William James and physiologist Carl Lange, independently proposed an idea that challenged commonsense beliefs about emotion. This idea, which came to be known as the James-Lange theory, is that people experience emotion because they perceive their bodies’ physiological responses to external events. According to this theory, people don’t cry because they feel sad. Rather, people feel sad because they cry, and, likewise, they feel happy because they smile. This theory suggests that different physiological states correspond to different experiences of emotion.
The physiologist Walter Cannon disagreed with the James-Lange theory, posing three main arguments against it: