Piaget's stages of development are part of a theory about the phases of normal intellectual development from infancy through adulthood, including thought, judgment, and knowledge.
The stages were named after psychologist and developmental biologist Jean Piaget, who recorded and studied the intellectual development and abilities of infants, children, and teens.
Piaget's four stages of intellectual (or cognitive) development are:
Sensorimotor. Birth through 2 years old
Preoperational. Toddlerhood through early childhood (2-7 years old)
Concrete operational. Ages 7-11 years old
Formal operational. Adolescence through adulthood, 12 years and older
Piaget acknowledged that some children may pass through the stages at different ages than the averages noted above. He also said some children may show characteristics of more than one stage at a given time.
