One of Piaget's most important contributions to psychology of learning was the idea of children who make sense of reality like inborn scientists working alone on the physical, logical and mathematical material of the world. Children develop cognitive structures on their own through many processes including adaptation, accommodation and assimilation (Pulaski, & Ann, 1980).
Piaget suggested four major stages, or "periods" of human development such as the sensory-motor, pre-operational, concrete-operational, and formal-operational. Over each of these four stages children and adolescents master various types of mental skills, and acquire the ability to use symbols and reason in abstract ways (Huitt and Hummel, 2003). Child's thinking develops gradually and systematically as he progresses through these stages.
Although Piaget admits that children do benefit from interactions with peers, such interactions in his opinion contribute insignificantly to the radical cognitive transformation. Piaget views cognitive development as biologically based process, and does not believe that the child is able to extend their cognitive capabilities beyond their stage of development. Correspondingly, Piaget does not find any use in teaching children principles that are beyond their current stage of cognitive development. During the process of cognitive development the child becomes increasingly social, and social factors begin to play more important role in the child's learning of moral judgments (Pulaski, & Ann, 1980).
Language comes about as the sensory-motor period ends and new cognitive tools develop. Piaget considers that infants are born with schemes operating at birth that he called 'reflexes' (Huitt and Hummel, 2003). Although in animals these reflexes control behavior throughout life, in human beings they act as adaptive tools that facilitate adaptation of the infant to environment. Piaget outlines the following four stages of cognitive development:
"Sensorimotor stage (infancy) - during this period the child demonstrates intelligence solely through motor activity and is unable to use any symbols. The child's knowledge the world gradually develops but is still because it relies exclusively on the experience of physical interactions. Initial symbolic abilities in the form of language develop only at the end of this stage;
Pre-operational stage (toddler and early childhood) - this phase involves demonstration of intelligence the use of symbols. The use of language gradually advances and becomes more complex, and simultaneously memory and imagination also develop though thinking still follows illogical nonreversible largely egocentric patterns;
Concrete operational stage (elementary and early adolescence) - the child demonstrates intelligence through systematic and logical use of symbols related to concrete objects. During this stage, reversible operational thinking develops which involves diminishing egocentric thinking;
Formal operational stage (adolescence and adulthood) - during this period the child demonstrates intelligence through the coherent and logical use of symbols that relate to abstract objects and concepts (Huitt and