piagets four stages

Psychologists have been interested in how and when mental abilities develop for many years. Cognitive development is how and when we develop and use mental abilities through out the life span.
Cognitive development can not be directly measured, therefore because infants brains are not fully mature at birth they are unable to explain their thoughts. This has led many early psychologists to believe that infants were not capable of much thinking.

Swiss psychologist Jean Piaget (1896 –1980) viewed cognitive capabilities of infants in a different way. He proposed that cognitive development occur as we adapt to the changing world around us. He described adaptation as the continuos process of using the environment to learn about the...