These are age-related stages and refer to certain accomplishments that should be achieved, by the child, at the end of each stage. The first stage of cognitive development is the Seniority stage, which lasts from birth to around two years of age. During this stage, children learn to coordinate their senses (hearing, sight, touch etc. ) with their motor abilities.
From two to seven years s the Pre-operational stage. Children of this age become capable of more sophisticated thinking. The Concrete operational stage lasts from about seven years of age to about twelve. These children put together what they have already learnt, with knowledge gained from new experiences. The final stage of cognitive development identified by Pigged, is the Formal operational stage. This lasts from twelve years of age onwards. People in this stage are capable of more complex thought processes.
During the Concrete operational stage (7 to 12 years), children should develop an understanding of the principle of conservation. Conservation refers to the idea that if an object alters its shape or appearance, its volume, mass, length or area will not change. A child with an understanding of conservation should be able to think logically and see that these qualities have not changed, even if they appear to have done so. Achievement of conservation of mass can be demonstrated with two small alls of plasticize.
A child is shown the plasticize and agrees that the balls are the same size. One of the balls is then squashed down. A pre-concrete operational child will probably decide that the ‘squashed’ ball is bigger, while a child at the Concrete operational stage should acknowledge that they are still the same weight or mass. This Illustrates the ability of the child to understand how the object has changed, not only see the beginning and end result.