Answer :
Explanation :

Jean Piaget was a cognitive psychologist who identified four stages of development: the sensorimotor stage from birth to 2 years, the preoperational stage from age 2 to age 7, the concrete operational stage from age 7 to 11, and the formal operational stage from age 11 to adult. He identified milestones that occur at each stage.   According to Piaget, the main task of the sensorimotor stage is for the child to learn the concept of object permanence, use senses and motor skills to understand the world.