Developmental Psychology : Childhood And Adoles... -

Previously thought to end at 18, recent research suggests actually extends into the early 20s or even the early 30s as the brain continues to reorganize for efficiency. Adolescent Development - Cleveland Clinic

: Children begin developing "self-concept" and sensitivity to others' evaluations as early as 24 months. The Transformation of Adolescence Developmental Psychology : Childhood and Adoles...

: According to Jean Piaget's theory, children progress through stages like sensorimotor (birth–2 years), where they learn through physical interaction, and preoperational (2–7 years), where symbolic thinking begins. Previously thought to end at 18, recent research