How did Jean Piaget use logical structures to study children’s cognitive development?

Jean Piaget studied children’s cognitive development by observing how they acquire and manipulate logical structures to understand the world. He viewed the child as a scientist who creates and recreates models of reality through interactions with their environment.123

Piaget identified four developmental stages, each defined by the child's increasing ability to use logical operations:14

• Sensorimotor (birth–2 years): Children master physical reflexes and begin to understand object permanence.23
• Preoperational (2–7 years): Children learn to manipulate their environment through symbolic thought and language but lack fully developed logical operations.12
• Concrete-operational (7–12 years): Logic emerges as children develop "operations"—flexible, reversible cognitive structures. They gain the ability to conserve quantities (recognizing that substance remains constant despite shape changes) and perform seriation (arranging objects by size or weight).13
• Formal-operational (12+ years): Adolescents develop the ability to reason systematically about hypothetical events, generate hypotheses, and evaluate their own thinking for inconsistencies.153

Piaget’s research relied on ingenious problem-solving tasks, where he analyzed children's errors to map their unique ways of viewing the world.2