Developmental psychology is the scientific study of age‐related changes throughout the human life span. A discipline of scientific inquiry, developmental psychology recognizes humans of all societies and cultures as beings who are “in process,” or constantly growing and changing. This discipline identifies the biological, psychological, and social aspects that interact to influence the growing human life‐span process. Beginning with Sigmund Freud (1856–1939) and Jean Piaget (1896–1980), the early focus of developmental psychology was on child development, or the maturation of children. Within the last 25 years, developmentalists—researchers who study human development—expanded their focus to include the study of the physical, motor, cognitive, intellectual, emotional, personality, social, and moral changes that occur throughout all stages of the life span.