According to Piaget, there are four main stages of development^[1], summarized by :

• The sensory-motor stage, before the age of 2-3, where children discover the world with their body (a body that they gradually learn to coordinate);
• The perceptual stage, between 3 and 7 years old, where children learn to open up to others and to the world around them;
• The analytical stage, between 7 and 11 years old, where children exercise their logic;
• The reflective stage, between 11 and 16 years old, where children perfect their reasoning and applie it to the abstract.

This is very instructive in the way we approach learning and concepts on a day-to-day basis with children. This is often forgot that intelligence is not innate, that it takes time and learning to develop some knowledge of the world. When we experiment, for example, with the permanence of objects for children at different stages of the sensory-motor stage, this become more obvious. While a child in stage 3^[2] of the sensory-motor stage is not aware that the object that disappears from his sight has not really disappeared, he has acquired this knowledge in stage 6^[3], even if his search is not yet optimal.

However, in this theory, children are considered as epistemic subjects (which is common among subjects at the same level of development) and not social ones, which reinforces the immaturity of their skills (de La Ville & Tartas, 2003^[4] & Montangero, 2001^[5]).