Jean Piaget a Swiss psychologist (1896–1980) studied in detail, the development of the mind specifically, how we learn to reason. He noticed that when young children take intelligence tests, they often give similar wrong answers. This set him to thinking that the children might be using some consistent, but incorrect, reasoning. It might even indicate that children go through some natural process as they learn how to reason.
Stimulated by such an intriguing possibility, Piaget set up a laboratory where he could give children of different ages problems. After years of testing, Piaget concluded that children do go through a natural process as they develop their ability to reason. This process has four stages: -
1. The sensorimotor stage (from birth to about age 2) During this stage, our understanding is limited to direct contact—sucking, touching, listening, looking. We aren't able to "think." During the first part of this stage, we do not even know that our bodies are separate from the environment. Indeed, we have yet to discover that we have toes. Neither can we recognize cause and effect. That is, we do not know that our actions cause something to happen.
2.The preoperational stage (from about age 2 to age 7) During this stage, we develop the ability to use symbols. However, we do not yet understand common concepts such as size, speed, or causation. Although we are learning to count, we do not really understand what numbers mean. Nor do we yet have the ability to take the role of the other. Piaget asked preoperational children to describe a clay model of a mountain range. They did just fine. But when he asked them to describe how the mountain range looked from where another child was sitting, they couldn't do it. They could only repeat what they saw from their view.
3. The concrete operational stage (from the age of about 7 to 12) our reasoning abilities are more developed, but they remain concrete. We can now understand numbers, size, causation, and speed, and we are able to take the role of the other. We can even play team games. Unless we have concrete examples, however, we are unable to talk about concepts such as truth, honesty, or justice.
4. The formal operational stage (after the age of about 12) we now are capable of abstract thinking. We can talk about concepts; come to conclusions based on general principles, and use rules to solve abstract problems. During this stage, we are likely to become young philosophers.