Careers in Psychology from the American Psychological AssociationPsychologists frequently are innovators, evolving new approaches from established knowledge to meet the changing needs of people, organizations and societies. They develop theories and test them through their research. As this research yields new information, these findings become part of the body of knowledge that practitioners call on in their work with clients and patients, as well as with organizations and communities. Psychology is a tremendously varied field. Psychologists conduct both basic and applied research, serve as consultants to communities and organizations, diagnose and treat people, and teach future psychologists and those who will pursue other disciplines. They test intelligence and personality. Many psychologists work as health care providers. They assess behavioral and mental function and well-being, study how human beings relate to each other and also to machines, and work to improve these relationships. And because the United States is undergoing sizable change in its population makeup, psychologists provide important knowledge and skills to help better understand diverse cultures.