Piaget's Theory: The 4 Stages of Cognitive Development

Background and Key Concepts of Piaget's Theory

Cognitive Development
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According to psychologist Jean Piaget, children progress through a series of four critical stages of cognitive development. Each stage is marked by shifts in how kids understand the world. Piaget believed that children are like "little scientists" and that they actively try to explore and make sense of the world around them.

Through his observations of his children, Piaget developed a stage theory of intellectual development that included four distinct stages:

  • The sensorimotor stage, from birth to age 2
  • The preoperational stage, from age 2 to about age 7
  • The concrete operational stage, from age 7 to 11
  • The formal operational stage, which begins in adolescence and spans into adulthood.

A Look at Piaget's Stages of Cognitive Development

  • The Sensorimotor Stage: During this stage, infants and toddlers acquire knowledge through sensory experiences and manipulating objects. It was his observations of his daughter and nephew that heavily influenced his conception of this stage.

    At this point in development, a child's intelligence consists of their basic motor and sensory explorations of the world. Piaget believed that developing object permanence or object constancy, the understanding that objects continue to exist even when they cannot be seen, was an important element at this point of development. By learning that objects are separate and distinct entities and that they have an existence of their own outside of individual perception, children are then able to begin to attach names and words to objects.
  • The Preoperational Stage: At this stage, kids learn through pretend play but still struggle with logic and taking the point of view of other people. They also often struggle with understanding the ideal of constancy.

    For example, a researcher might take a lump of clay, divide it into two equal pieces, and then give a child the choice between two pieces of clay to play with. One piece of clay is rolled into a compact ball while the other is smashed into a flat pancake shape. Since the flat shape looks larger, the preoperational child will likely choose that piece even though the two pieces are exactly the same size.
  • The Concrete Operational Stage: Kids at this point of development begin to think more logically, but their thinking can also be very rigid. They tend to struggle with abstract and hypothetical concepts. At this point, children also become less egocentric and begin to think about how other people might think and feel. Kids in the concrete operational stage also begin to understand that their thoughts are unique to them and that not everyone else necessarily shares their thoughts, feelings, and opinions.
  • The Formal Operational Stage: The final stage of Piaget's theory involves an increase in logic, the ability to use deductive reasoning, and an understanding of abstract ideas. At this point, people become capable of seeing multiple potential solutions to problems and think more scientifically about the world around them.

It is important to note that Piaget did not view children's intellectual development as a quantitative process; that is, kids do not just add more information and knowledge to their existing knowledge as they get older. Instead, Piaget suggested that there is a qualitative change in how children think as they gradually process through these four stages. A child at age 7 doesn't just have more information about the world than he did at age 2; there is a fundamental change in how he thinks about the world.

To better understand some of the things that happen during cognitive development, it is important first to examine a few of the important ideas and concepts introduced by Piaget. The following are some of the factors that influence how children learn and grow:

Fundamental Concepts

Schemas: A schema describes both the mental and physical actions involved in understanding and knowing. Schemas are categories of knowledge that help us to interpret and understand the world.

In Piaget's view, a schema includes both a category of knowledge and the process of obtaining that knowledge. As experiences happen, this new information is used to modify, add to, or change previously existing schemas.

For example, a child may have a schema about a type of animal, such as a dog. If the child's sole experience has been with small dogs, a child might believe that all dogs are small, furry, and have four legs. Suppose then that the child encounters an enormous dog. The child will take in this new information, modifying the previously existing schema to include these new observations.

Assimilation: The process of taking in new information into our already existing schemas is known as assimilation. The process is somewhat subjective because we tend to modify experiences and information slightly to fit in with our preexisting beliefs. In the example above, seeing a dog and labeling it "dog" is a case of assimilating the animal into the child's dog schema.

Accommodation: Another part of adaptation involves changing or altering our existing schemas in light of new information, a process known as accommodation. Accommodation involves modifying existing schemas, or ideas, as a result of new information or new experiences. New schemas may also be developed during this process.

Equilibration: Piaget believed that all children try to strike a balance between assimilation and accommodation, which is achieved through a mechanism Piaget called equilibration. As children progress through the stages of cognitive development, it is important to maintain a balance between applying previous knowledge (assimilation) and changing behavior to account for new knowledge (accommodation). Equilibration helps explain how children can move from one stage of thought into the next.

Jean Piaget's Background

Jean Piaget was born in Switzerland in 1896. He published his first scientific paper at the tender age of 10—a 100-word description of an albino sparrow in a naturalist magazine. Between the ages of 15 and 19, he published numerous papers on mollusks and was even offered a job as a curator at a museum, although he had to decline the offer since he still had two years of high school to complete.

While he developed an interest early on in how people come to know the world around them, he didn't receive any formal training in psychology until after he had completed his doctoral degree at the University of Neuchatel. After receiving his Ph.D. degree at age 22 in natural history, Piaget formally began a career that would have a profound impact on both psychology and education. After studying briefly with Carl Jung, he happened to meet Theodore Simon, one of Alfred Binet's  collaborators. Simon offered Piaget a position supervising the standardization of the intelligence tests developed by Binet and Simon.

Piaget developed an interest in the intellectual development of children. Based on his observations, he concluded that children were not less intelligent than adults, they simply think differently. Albert Einstein called Piaget's discovery "so simple only a genius could have thought of it."

Piaget's stage theory describes the cognitive development of children. Cognitive development involves changes in cognitive process and abilities. In Piaget's view, early cognitive development involves processes based upon actions and later progresses to changes in mental operations.

Piaget's interest in child cognitive development was influenced by watching his 13-month-old nephew, Gerard, at play. By chance, Piaget observed the toddler playing with a ball. When the ball rolled under a table where the boy could still see it, Gerard simply retrieved the ball and continued playing. When the ball rolled under a sofa out of his sight, however, the child began looking for it where he had last seen it. This reaction struck Piaget as irrational.

Piaget came to believe that children lack what he referred to as the object concept—the knowledge that objects are separate and distinct from both the individual and the individual's perception of that object.

Jean Piaget set out to study his daughter Jacqueline as she developed through infancy, toddlerhood, and childhood. He quickly noted that during the early months of his daughter's life, she seemed to believe that objects ceased to exist once they were out of her sight. At nearly a year, she started to search actively for objects that were hidden from her view although she made mistakes similar to the one Gerard made. By 21 months, Jacqueline had become skilled at finding hidden objects and understood that objects had an existence separate from her perception of them.

Piaget's observations of his nephew and daughter reinforced his budding hypothesis that children's minds were not merely smaller versions of adult minds. Instead, he proposed, intelligence is something that grows and develops through a series of stages. Older children don't just think faster than younger children, he suggested. Instead, there are both qualitative and quantitative differences between the thinking of young children versus older children.

Final Thoughts

One of the most important elements to remember of Piaget's theory is that it takes the view that creating knowledge and intelligence is an inherently active process. "I find myself opposed to the view of knowledge as a passive copy of reality," Piaget explained. "I believe that knowing an object means acting upon it, constructing systems of transformations that can be carried out on or with this object. Knowing reality means constructing systems of transformations that correspond, more or less adequately, to reality."


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Santrock, John W. (2008). A topical approach to life-span development (4 ed.). New York City: McGraw-Hill.

Piaget, J. (1977). Gruber, H.E.; Voneche, J.J. eds. The essential Piaget. New York: Basic Books.

Piaget, J. (1983). Piaget's theory. In P. Mussen (ed). Handbook of Child Psychology. 4th edition. Vol. 1. New York: Wiley.

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