Piaget, a cognitive psychologist, suggested 4 (four) stages of cognitive development of individuals, namely:
1. Sensory-Motor Stage (0-2)
Sensory-motor intelligence is seen as a practical intelligence (practical intelligence), is worthwhile to learn to do to the environment before be able to think about what he was doing. Individual intelligence at this stage is still primitive, but it is a very basic intelligence means to be cornerstone types of specific intelligence that would have children someday. Before the age of 18 months, children are not familiar with object permanence. This means that any object which he didn’t see, he didn’t touch, or didn’t he heard are didn’t exist even though it actually exists. In the range 18 to 24 months before child’s ability to object permanence appears gradually and systematically.
2. Pre-Operational Stage (2-7)
At this stage the child already has a perfect mastery of object permanence. This means that these children have remained the awareness of an object that must exist or there are unusual; although the body had he left or was not seen, heard or touched again. Thus, the view of the existence of these objects different from the sensory motor period, which is no longer rely on mere observation. In a period marked by a self-centered and in this period allows the child to develop deferred-imitation, insight learning and language skills, and using words correctly and be able to express short sentences, but effective.
3. Concrete-operational stage (7-11)
In a period marked by the addition of capabilities called system of operation (unit-step thinking) is useful to coordinate thoughts and ideas with specific events in his thought. Basically, the child’s cognitive development in terms of its characteristics is similar to the cognitive abilities of adults. But there is limited capacity in coordinating his thought. In this period a new child can think systematically about the objects and events of the concrete.
4. Formal-operational stage (11-Adult)
In this period a teenager has a good ability to simultaneously coordinate and sequence of two kinds of cognitive abilities, namely:
Capacity use hypothesis; ability to think about something, especially in terms of solving problems by using the basic assumptions that are relevant to her environment and response capacity to use abstract principles.
Capacity to use abstract principles; the ability to learn the lesson materials are widely abstract and profound.
By using the measurement results of intelligence tests that include the General Information and Verbal Analogies, Jones and Conrad (in Abin Loree Shamsuddin M, 2001) showed that the rate of development of intelligence take place very rapidly to adolescence and then gradually decreased.
Peak growth generally achieved at the end of late adolescence. Changes very thin until the age of 50 years, and after that happened plateau (steady state) until the age of 60 years subsequent gradual decline.
