Psychology is defined as the scientific study of the mind and behavior. It has evolved from originally meaning the study of the soul to focusing on consciousness, behavior, and mental processes. Some early schools of thought in psychology included structuralism, functionalism, Gestalt psychology, behaviorism, psychoanalysis, humanistic psychology, and cognitive psychology. Modern psychology includes various branches and applications such as abnormal, biological, cognitive, developmental, health, and social psychology. Nursing can apply principles of psychology to improve patient interactions, assessments, care plans, and communication skills.