According to a famous psychologist, Jean Piaget, human beings move through four specific stages of cognitive development. From his point of view, kid’s mind grows by interacting with his physical environment: through the interaction with the world around them, they continually add new knowledge and adapt previously ideas to the new information. But the cognitive development is far more complex and therefore J. Piaget suggested a four-stage theory of cognitive development that describe how we learn in different phases of our lives:

1. Sensory motor stage (0-2years); this is the time when babies experience the world through their movements and sensations:

• they learn through basic actions such as sucking, grasping, looking, and listening;
• they understand that people and objects do not disappear just because they are hidden (this phenomenon is called ‘object permanence’);
• they realize that their actions can cause things to happen in the world around them.

2. Pre-operational stage (2 – 6-7 years);  at this stage children have the following characteristics

• they begin to think symbolically and learn to use words and pictures to represent objects;
• children at this stage tend to be egocentric and struggle to see things from the perspective of others;
• while they are getting better with language and thinking, they still tend to think about things in very concrete terms. In fact, they struggle with the idea of 'reversibility'. For example, it is hard for them to mentally reverse the process by which a ball of clay smashed flat can be rolled back into a ball.

3. Concrete Operational Stage (6-7 – 11-12 years); in this period children start:

• to think logically about concrete events;
• to understand that a certain quantity will remain the same despite of the container, shape, size etc. (idea of ‘conservation’).

4. Formal Operational Stage (12 – rest of our lives): by now, our reasoning is expanding to include more abstract thinking, problem solving and hypothetical questions.