- Sensorimotor Stage (0-2 years): Understanding the world through sensory experiences and physical actions. Key concept: Object permanence.
- Preoperational Stage (2-7 years): Use of symbols, language development, egocentric thinking. Key concepts: Symbolic play, egocentrism.
- Concrete Operational Stage (7-11 years): Logical thinking about concrete events, understanding of conservation. Key concepts: Conservation, reversibility.
- Formal Operational Stage (12+ years): Abstract and hypothetical thinking. Key concept: Abstract logic.