Jean Piaget was a Swiss Psychologist who developed a Theory of Cognitive Development which attempted to go beyond the simple measure of mental capacity that is IQ and achieve a more in-depth understanding of a child’s mental capacity. It was widely believed, during the 1930s, that children were simply worse thinkers than adults. However, through a series of clever tests, Piaget (1936) proved that children think in completely different ways to adults and, moreover, their ability to reason compounds such that one form of logic leads to improved versions as the child develops. Piaget’s theory had four stages of cognitive development.


Sensorimotor – The sensorimotor stage lasts from birth until around age two. This is a stage of discovery for the child. The child begins to examine the relationships between actions and the consequences of those actions. For example, a child begins to learn that, if they push a spoon to the edge of a table, it will fall. A child also begins to develop the concept of self. The child learns that they are separate from the outside world and that the hand is a part of themselves but the spoon is not. Additionally, the child learns that it is able to take actions and manipulate the environment around them. They become more object-oriented and may play with a rattle or a set of keys, for example, for its enjoyment. During this stage, the child learns Object Permanence which is the understanding that when an object is out of sight it does not cease to exist. Piaget tested this by placing objects under a cloth in front of the child. An 8 month old child will stop and lose interest almost immediately but a 1 year old will actively search for the object. At this point, the child understands that the object continues to exist and has a mental picture of the object. This is the first sign that the child has developed Short Term Memory.

Pre-Operational – This stage lasts from 2 years to 7 years of age and is the stage during which children develop language. At this stage, children are able to think symbolically. For example, during play, you might see a child pretending that a stick is a sword or a gun. A child’s speech also demonstrates their ability to think symbolically. However, while a child’s mind can think symbolically, it has trouble thinking logically and cannot manipulate information in the mind. Piaget (1936) proved this through Conservation Experiments. There were two kinds of there: conservation of mass and number.

Conservation of mass – This experiment may involve a child being given two glasses with an equal amount of liquid inside. The experimenter will then pour one of the glasses into a longer glass in font of the child without any liquid being added. The child will then be asked which contains more liquid and, at this stage, will answer that the larger container has more despite nothing being added. Additionally, the same experiment can be conducted with two clay balls of the same size. The experimenter will roll one into a cylinder and the child will then identify the cylindrical one as the larger one.

Conservation of Number – This experiment involves a child being shown two rows of coins containing the same amount. The child will identify them as the same. However, after the experimenter spreads out one of the lines, the child will identify that one as the one that has more.

Concrete Operational – This stage lasts from the age of 7 until 12. By this stage, a child has mastered conservation and become far less egocentric. The child now uses some logic and abstract thought but only in realistic terms that applies to their own experience. They still find it difficult to understand higher abstract thought.

Formal Operations – This is the final stage and begins at around age 12. During this stage, the child improves their ability to think symbolically. They begin to consider abstract ideas such as morality or the future. The huge leap in the education curriculum at this stage demonstrates this increase in mental capacity.


Piaget (1952) developed the idea of schemata according the children’s cognitive developments. Piaget (1952) defined schemata as “a cohesive, repeatable action sequence possessing component actions that are tightly interconnected and governed by a core meaning”. That is to say, it is a way of organising knowledge into mental plans based on the child’s day-to-day experiences. For example, when a person goes to the cinema, they access the behaviours of buying a ticket, popcorn, finding a seat and enjoying the film and follows this schema each time they go to the cinema.

He identified three kinds of schemata: behavioural schemata relating to objects and physical experiences, symbolic schemata, used to represent abstract aspects of experience and operational schemata, used for mental activities using thoughts such as mathematics. Piaget believed that children’s schemata develop and become more advanced as the child ages. Additionally, a child will assimilate new information from the environment and add this knowledge to their existing schemata. However, if the child encounters something with the same traits as an existing schema, it must accommodate this by creating a new schema. For example, a child develops a schema for car but does not know the difference between a car and a truck so it must create a new schema to differentiate the two. When a child’s existing schema are sufficient for describing their current experiences, they are said to be in equilibrium.


Some criticisms of Piaget’s Theory of Cognitive Development are:

  • Piaget may have understated the role of individual differences in the cognitive ability of children
  • No controls were set during the experimentation so there is nothing to measure against
  • Stage theories age limits may not cohere to the cognitive ability of all children. Moreover, the age groups may shift due to the Flynn Effect


Piaget, J. (1936). Origins of intelligence in the child. London: Routledge & Kegan Paul.

Piaget, J., & Cook, M. T. (1952). The origins of intelligence in children. New York, NY: International University Press.

Leave a Reply