Effects theory or media influence theory refers to the assertion that media have direct, indirect, and tangible effects on its consumers, on their behavior and psychological development, and on society at large. Theories of media effects are fundamental to the study of communications and encompass a wide-ranging body of approaches, methodologies, and applications relevant to media studies, psychology, and sociology. This entry discusses early research on media effects that led to the powerful effects model, the emergence of the limited effects model, and more recent research on media effects from a variety of perspectives.