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 The growth of the brain is followed by a surge in cognitive abilities. maximum height. •Girls –age 20 yr. •Boys – age 22 yr. •Lasts until age 40 yr. Middle Adulthood. •Ages yrs. Late (old) Adulthood. •Age 60 until death.