Piaget's Stages of Cognitive Development: The 4 Stages Explained

The four stages at a glance

The ages are approximate. Textbooks draw the second boundary at 6 or 7, and Piaget himself placed the arrival of formal operations at about 12 to 15 and said the pace varies between children and between cultures. What the theory fixes is the order, not the calendar.

How the theory began: wrong answers on a reasoning test

In Paris, where he studied from the autumn of 1919, the young Swiss biologist was given the use of Alfred Binet’s former laboratory at a Paris school by Théodore Simon, Binet’s co-author on the first intelligence test. Simon asked him to standardise Cyril Burt’s reasoning tests on Parisian children. Piaget wrote later that scoring right and wrong answers was useful for diagnosis, but that the reasons for the failures were far more interesting. He began questioning children about how they reached their answers, and found that the mistakes of younger children were not random: they reflected a different way of thinking.

That is the core idea of the whole theory, and the reason it sits next to IQ. An IQ test counts how many items a person gets right compared with others of the same age; Piaget wanted to know what kind of thinking produced the answer.

The building blocks: schemas, assimilation and accommodation

• Schemas are mental models a child uses to sort and interpret experience — for example, “things with four legs and fur are dogs”.
• Assimilation is fitting something new into a schema the child already has: the first cat gets called a dog.
• Accommodation is changing the schema when it no longer fits: cats become their own category.

Moving back and forth between the two is how, in Piaget’s view, understanding grows. The child is not filled with knowledge from outside; the child constructs it.

Stage 1: Sensorimotor (birth to about 2)

Babies learn by looking, grasping, sucking and moving, and by noticing what their actions do. The milestone of the stage is object permanence: understanding that something still exists when it is out of sight. A young baby may lose interest in a toy hidden under a blanket; an older one lifts the blanket. By the end of the stage, children begin to represent things in their minds, which opens the way to language and imitation.

Stage 2: Preoperational (about 2 to 7)

Language takes off, and children use words, drawings and pretend play to stand for things — a banana becomes a telephone. Their reasoning, though, is still tied to how things look. Two traits define the stage:

• Egocentrism: difficulty taking another person’s point of view — not selfishness, but not yet grasping that someone else sees or knows something different.
• No conservation yet: pour water from a short, wide glass into a tall, thin one, and a preoperational child will usually say the tall glass has more, because the level is higher.

Stage 3: Concrete operational (about 7 to 11)

Children now reason logically about real objects and events. They understand conservation — the amount of water stays the same whatever the shape of the glass — and can mentally reverse an action, sort things into categories and put them in order. The limit is in the name: logic works best on things they can see, handle or imagine concretely, and less well on pure abstractions.

Stage 4: Formal operational (from about 11 or 12)

Adolescents can reason about ideas as well as objects: they can form hypotheses, test them systematically, follow an argument from premises they do not believe, and think about what could be rather than only what is. This is the reasoning behind algebra, science and the deductive and inductive reasoning that adult thinking relies on.

Piaget later softened the idea that this stage is simply reached and applied everywhere. In a 1972 paper he wrote that people apply formal operations to different areas depending on their aptitudes and professions, and that it is best to test a young person in a field relevant to their career and interests.

Is a Piaget stage the same as IQ?

No — they answer different questions. A Piagetian stage describes what kind of reasoning is typical at an age, and nearly everyone moves through the same sequence. An IQ score is a ranking: it compares one person’s performance with others of the same age, which is why average IQ is 100 at every age. A child can be well ahead of peers on an IQ test and still be in the stage typical of their age.

The two do measure overlapping abilities. A 2021 study of three groups of Austrian children, aged 4 to 10, gave them both Piagetian tasks and Raven’s matrices. The average correlation between IQ and the Piagetian tasks was .51, and in factor analyses both loaded on a common factor of general intelligence. Mental speed was more closely tied to the IQ tests, while the Piagetian tasks were more closely tied to parents’ education.

What later research changed

• Babies know more, earlier. Piaget’s tests relied on infants searching for a hidden object. Later research measured how long infants look at events that violate their expectations instead, and reported object permanence much earlier — one 1985 paper is titled “Object permanence in five-month-old infants”. Whether that reflects built-in knowledge or perception that sharpens over the first six months is still debated.
• Stages or a slope? Several later studies support a more continuous model of development than four distinct stages, and find that children reach some milestones earlier than Piaget described.
• Formal operations are not universal in one form. As Piaget himself acknowledged, the pace differs across cultures and adults apply abstract reasoning unevenly, strongest in their own fields.
• Many criticisms miss the theory. A 1996 review in Psychological Review argued that most common criticisms rest on misreadings of Piaget, ignore how he revised the theory after 1970, or try to settle empirically what first needs to be clarified conceptually.

Piaget vs Vygotsky

Lev Vygotsky is the name most often set against Piaget. A 2012 review found many resemblances between the two — both saw the child as an active builder of knowledge — and located the crucial difference in where development comes from. Piaget emphasised the child’s own transformation and reconstruction of knowledge, with exchanges between equals as a source of growth; Vygotsky gave more weight to transmission and social influence, including guidance from adults and more knowledgeable others.

How to remember the stages

Keep the order by the initials S-P-C-F — sensorimotor, preoperational, concrete operational, formal operational — with a phrase such as “Some People Can Fly”. Then attach one milestone to each: the hidden toy, the pretend telephone, the two glasses of water, the hypothesis. The milestones are what exam questions ask about.

Trust and scope notes

This page explains a psychological theory in general terms. It is not a way to assess a child’s development, and a stage is not a diagnosis; questions about an individual child belong with a paediatrician or child psychologist. Our IQ test is for adults aged 18 and over; it does not assess children or Piagetian stages. For parents, our guide to IQ tests for kids explains how children are actually assessed.

IQ Revealed is not affiliated with, endorsed by or connected to the Fondation Jean Piaget, the researchers, universities, publishers or test publishers named or referred to on this page, including the publisher of Raven’s matrices. Their names are used only to identify the work being described.