Action of using one's mind to produce thoughts, or covert symbolic responses to stimuli. Theories of thought and thought processes have concentrated largely on directed thinking, including problem solving. At the beginning of the 20th century, researchers focused on studying mental associations. Theorists of Gestalt psychology in the 1920s and '30s believed the elements of thought to be in the nature of patterns elicited from experience. Today these elements are often regarded as bits of information undergoing processing. See alsocognitive psychology, information processing.