Human emotions are complex. The six base emotions are: Fear, Anger, Joy, Sadness, Disgust, and Surprise/Shock. These emotions combine in different ways to form other emotions, including compassion, boredom, embarrassment, rage, hunger, and more. They express positive or negative reactions to external and internal stimuli. According to modern psychology, emotion, behavior and cognition influence each other. Thus, each emotion distinctly affects human motivation, nervous function, learning, physical acts, physiological arousal and communication with others.
Robert Plutchik, Paul Ekman, Wallace Friesen, Carrol Izard and Silvan Tomkins are among the names that have made significant contributions to the study and classification of human emotions. They believe that certain emotions can be catagorized as base or secondary.