Childhood is the age span ranging from birth to adolescence. According to Piaget's theory of cognitive development, childhood consists of two stages: preoperational stage and concrete operational stage. In developmental psychology, childhood is divided up into the developmental stages of toddlerhood (learning to walk), early childhood (play age), middle childhood (school age), and adolescence (puberty through post-puberty). Various childhood factors could affect a person's attitude formation.
Early childhood is a stage in human development. It generally includes toddlerhood and some time afterwards. Play age is an unspecific designation approximately within the scope of early childhood. Some age-related development periods and examples of defined intervals are: newborn (ages 0–5 weeks); infant (ages 5 weeks – 1 year); toddler (ages 1–3 years); preschooler (ages 3–5 years); school-aged child (ages 6–11); adolescent (ages 12–17).
Adolescents are simply those people who haven't as yet chosen between childhood and adulthood. For as long as anyone tries to hold on to the advantages of childhood—the freedom from responsibility, principally—while seeking to lay claim to the best parts of adulthood, such as independence, he is an adolescent. [...] Eventually most people choose to be adults, or are forced into it. A very few retreat into childhood and never leave it again. A large number remain adolescents for life.
Gene Wolfe, The Book of the Short Sun, Volume 2: In Green's Jungles (2000), Ch. 23.
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