Created a process of stages linked to ages and behaviours: Sensori-motor; aged 0-2, children gaining understanding of environment by using senses and actions. So learn object permanence and stranger anxiety.
Pre-operational; 2-7 yrs, use symbols to represent objects. Classify objects by a feature (e.g. colour). Pretend play develops & egocentric thinking.
Concrete operational; 7-11 yrs, reason logically about concrete events, see things from others POV. Classify objects based on numerous features (e.g. shape, colour, size). Conservation, basic understanding of maths, geometry and physics.
Formal operational; 11+ yrs, adolescent understand and reason logically about abstract concepts, create and test hypotheses. Abstract logical thinking & moral reasoning.