Mark N. Skelton, MA, EMDR
Basic Trained EMDR Clinician | Cognitive Skills Trainer
Doctoral Student, Clinical Psychology (KCU)

Jean Piaget & Cognitive Development

Jean Piaget, a Swiss psychologist and genetic epistemologist, is a prominent figure in developmental psychology. Piaget’s theory regarded cognitive development as a process which occurs due to biological maturation and interaction with the environment (Piaget, 1936). According to his theory, cognitive maturation is seen as involving qualitative changes that become more sophisticated as the child’s intellect develops (Piaget & Inhelder, 1969).

In Piaget’s cognitive theory, children progress from one stage to another through adaptation and cultivating their schemas. Piaget & Cook (1952) defined schemas as repeatable action sequences governed by core meanings that are the basic building blocks of knowledge and mental representations in children. For example, a child may first develop the schema of a cat as having whiskers, four legs and a tail. If their experience has only been with black cats with green eyes, then they may believe this is the only type of cat that exists. However, new information and experiences modify schemas to include Siamese cats, with white fur and blue eyes, and expands the feline class further to lions, tigers, and cheetahs.

Assimilation, Accommodation and Equilibrium

Development occurs through the processes of assimilation, accommodation and equilibrium. Assimilation is the adaptive process in which a child brings in new information into an existing body of knowledge. Piaget & Inhelder (1969), believed assimilation is a two way process in which external stimuli is modified to fit into existing schemas, whereas accommodation is the modification of internal schemes to fit reality. In other words, assimilation is like changing the key to fit the lock and accommodation is changing the lock to fit the key. A balancing act between these two concepts is needed to open the door of a child’s cognitive development. This balancing act is known as equilibrium (Piaget & Inhelder, 1969).

Through the aforementioned operations, children adapt to the external world through the habitual, and ultimately intentional, use of their biological and cognitive abilities. There are four identifiable stages Piaget uses to explain cognitive development; Sensorimotor, Preoperational, Concrete Operations and Formal Operations. Each stage is separated by age group and their respective cognitive goal(s). For purposes of the current subject matter, this blog will only address the first two stages since they cover 0-7 years old.

Sensorimotor Stage (0-2 years old)

The ‘Sensorimotor Stage’ takes place between birth and about 2 years of age. During this time, a child is exploring the senses that were brought online during neurodevelopment. See my previous blog for stages of brain development. Early on, a child’s behavior is biologically driven and primarily attributed to reflexes (Piaget & Inhelder, 1969). If you recall, this is during the same time when neuron growth and myelination is occurring. The child’s schemas and mental representations advance from simple to complex as infants begin to physically manipulate their external environment (Piaget & Inhelder, 1969). The ultimate goal of this stage is “Object Permanence”, where a child is cognitively able to comprehend objects still exists even though hidden and /or out of sight (Piaget & Inhelder, 1969).

Preoperational Stage (2-7 years old)

The ‘Preoperational Stage’ follows and generally ranges from the ages of 2-7 years old. This second stage is usually characterized by the limitations of rational thinking patterns. Conservation is a key concept that captures the undeveloped abilities of logic and reasoning in children (Piaget & Inhelder, 1969). In tasks of conservation, the amount of something stays the same while its appearance is changed. For example, flattening a sphere of Play-Doh into a ‘pancake shape’ or pouring the same volume of water into a narrower container. Consequently, some children are not able to understand the amounts are the same even though in different forms.  Children in this stage of development generally do not have the mental capacity to manipulate or transform objects. This means they are usually unable to perform a reverse mental task to return an object back to its original state. An explanation for this phenomenon is that toddlers and preschoolers tend to make intuitive judgments based on how an object appears in the ‘here-and-now’ (Piaget & Inhelder, 1969).

It is also during this stage when language and grammar evolve. Piaget’s theory on language development believed that children needed to accomplish mental competence in previous stage before language acquisition can begin (Piaget & Gabain, 1926). By this time, cognitive functioning is heavily influenced by symbolism, egocentric thinking and fantasy. Piaget believed these dynamics explain why children need play as a fundamental medium of communication and talk to others as if they are alone and thinking aloud (Piaget & Gabain, 1926). As we approach section on screen time use, keep in mind that language development is another cognitive mechanism resulting from interactions with the environment.


In summary, young and developing children are believed to go through a systematic process in developing cognitive skills and psychological capacities. Understanding these dynamics is extremely important in regards to parenting and educational endeavors. When adults and educators are aware of the strengths and limits of children in this age group they can tailor teaching, discipline and rewards in an age appropriate manner. Our next blog will discuss the importance of the parent-child relationship through the attachment theories.




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.

Piaget, J. & Gabain, M. (1926). The language and  thought of the child. Harcourt Brace & Company, Inc.

Piaget, J. & Inhelder, B. (1969). The psychology of the child. Basic Books.

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