A field of psychology which examines how human behavior changes as a person matures through focusing on biological, emotional, physical, cognitive, and social changes that are age-related, sequential, and long-lasting.

Developmental psychologists study how characteristics and behaviors first appear and how and when they change. They study the relationships between different types of development, such as cognitive and social, as well as individual variations in development, both normal and deviant. Initially, developmental psychology focused on childhood but was subsequently expanded to cover changes that occur over the entire life span, from the intrauterine environment through childhood,