Fear

Fear is an unpleasant emotion that arises in response to perceived dangers or threats. Fear causes physiological and psychological changes. It may produce behavioral reactions such as mounting an aggressive response or fleeing the threat, commonly known as the fight-or-flight response. Extreme cases of fear can trigger an immobilized freeze response. Fear in humans can occur in response to a present stimulus or anticipation of a future threat. Fear is involved in some mental disorders, particularly anxiety disorders.