YA is a time of peak vitality though biological systems begin to decline slightly during the 30's. There is little physical development at this time.
EC is a time of rapid physical growth Bodies are getting longer more slender Bones are hardening
Schaie proposes that adult cognition is defined by its flexibility. Piaget's cognitive development theory considers the YA brain to be at the highest operational level. Post formal thought is more complicated and based in reality.
Piaget's cognitive development theory places children in early childhood at the preoperational stage which means their language and thinking abilities are still rudimentary. Memory in children is much like a computer the information is encoded and retrieved. Vygotsky proposed that children can be guided to solve problems that are too difficult if children show them how.
Though young adults in their early 20's are in the last stages of emotional development there is little happening in emotional development. At this time many young adults are focused on finding intimate romantic and platonic relationships and furthering their careers.
Children at this stage are trying to learn to control their emotions which helps cope with the anxiety and fear that children at this age experience. Their lack of emotional understanding means they lack empathy which can lead to more aggressive behavior. They begin to develop social competence by age 4 and by age 6 it is well established.