For 10 points, name this Swiss psychologist known for his theory of cognitive development.
This psychologist classified reactions as primary, secondary, and tertiary circular, and described mental structures that he called "schemas." He studied how children understand that things that can no longer be seen (*) still exist, a theory he called object permanence. His best-known theory classifies child maturation into four periods known as sensorimotor, preoperational, concrete operational and formal operational. For 10 points, name this Swiss psychologist known for his theory of cognitive development.
This psychologist classified reactions as primary, secondary, and tertiary circular, and described mental structures that he called "schemas."
Jean {Piaget}