Emotions are caused by physiological reactions

Many different physiological responses, such as an increased heart rate, sweating, and trembling, are strongly associated with emotional experiences. As a result, many people have made the "common sense" assumption that their emotions cause these physical sensations. The James-Lange theory of emotion inverts the common sense understanding of emotion, arguing that physiological responses to stimuli occur first and cause the emotions, not the other way around. Psychologist William James and physiologist Carl Lange each independently developed this argument in the late 19th century, leading to this theory of emotion being known as the James-Lange theory. Since that time, some studies have shown a link between specific physiological responses and emotions, including an association between elevated adrenaline levels and fear.