Psychology is the scientific study of human behavior and mental processes. It has four main goals: description, explanation, prediction, and control. Early schools of thought included structuralism, functionalism, Gestalt psychology, behaviorism, and psychoanalysis. Modern perspectives include psychodynamic, behavioral, humanistic, cognitive, biological, and sociocultural approaches. Key branches of psychology are developmental, personality, social, industrial/organizational, clinical, counseling, educational, health, and forensic psychology. Research methods include descriptive research, correlational research, experimental research, and quasi-experimental research.