Complex sentence: Horizontal and vertical décalage are terms coined by renowned developmental psychologist Jean Piaget, who is credited for the four Stages of Cognitive Development: sensorimotor, preoperational, concrete operations, and formal operations.
Split into simpler sentences: Horizontal and vertical décalage are terms coined by developmental psychologist Jean Piaget. He is credited with delineating Piaget's four Stages of Cognitive Development: sensorimotor, preoperational, concrete operations, and formal operations.