At one extreme is the idea that emotions are the experience of physiological changes such as the increased heart rate that accompanies anger. Researchers at the other extreme see emotions as purely cognitive, merely another form of thought. Although they have had some success in identifying such universals, their studies have been thwarted by a variety of factors. The generation of emotions is apparently influenced by, among other factors, goals, diet, attitude, expectation, perception, and culture. There is presently no widely accepted, comprehensive theory of emotions, although much has been learned.
Emotions can even be contagious.
You may recall a favorite teacher who was so enthusiastic about a subject that you became interested in it too. Or, you may have watched an actor express an emotion so effectively that its impact, not only on the other characters in the drama, but also on the audience, was electrifying. Actors study posture, gestures, facial expressions, and vocal intonation to find the best ways to communicate their character's feelings. An effective actor is a master of affect. An example of the impact of emotional expression occurs in the film Schindler's List when the one-armed Jewish machinest goes to thank Schindler for giving him a job.