In context with cognitive development 2 very famous person comes to mind. J.B.Watson and of course Jean Piaget.
These two psychologists had different but very similar theories about a cognitive development process during the growth of an infant.
For John B.Watson children were born as "blank slates", in other words this means he thought children learn things only through experiences.
Very similar t othis Jean Piaget said: "Children develop in sequences, series and stages."
Now let's take a look at these different stages Piaget talked about.
He categorized infant's development into 4 different stages. In his opinion the ages, where these facts occur, may differ but the sequence always remains the same.
Sensorimotor
Sensorimotor is the first one of Piaget's stages. According to Piaget this stage occurs from birth to approximately 2nd year of the child. In this stage there is a lack of language, the child has no use for symbols or any mental representations for objects. Important to mention is that in this stage reflexive responds end, in other words this means the child is able to produce interesting stimulations. Furthermore it develops object concepts and a basic language.
As an example: an infant, who is in the sensorimotor stage, shows only interest to an object for example to a toy, when he sees it, in the absence of the object it doesn't look for it or searches the object.
Preoperational
This is the 2nd stage and usually occurs between 2 and 7 years. In this stage the infant begins to represent the mentally. But important to mention is that the infant's thoughts are egocentric. It does not focus on 2 different aspects of a situation. This affects to a lack of conversation. Other characteristics are animisim, artificialism, objective responsibility for wrongdoing etc.
In this concept, we do have an example too: A child is not able to say that both bottle have the same amount of fluid, when one of the bottles is thin and long and the other flat and short, although the volume is the same.
Concrete Operational
The 3rd stage occurs approx. from 7 years to 12 years. Now logical mental actions, conversation concepts, understanding the opinions of others, ability to classify objects into different series and comprehension for basic relational concepts begin.
Formal Operational
This is the 4th and last one of Piaget's stages. Finally the child develops an adult thought , deductive logic, consideration of various possibilities for problem solving, abstract thoughts and hypothesis.
