Piaget's stages of cognitive development

What it says

Piaget's account is that a child builds working models of the world, called schemas, and runs into them. New facts that fit are taken in. Facts that do not fit force the model to change. He called the first assimilation and the second accommodation.

Out of that come four stages, each with a kind of thinking the one before could not do. The order is the claim: a child does not skip a stage, because each one is built out of the last.

The four stages

The marker beside each stage is the task Piaget used to show it.

1. Sensorimotor, birth to about 2

   Thinking happens in action. The marker is object permanence: a hidden toy stops being searched for, and later is searched for.

2. Preoperational, about 2 to 7

   Symbols arrive, in words and pretend play. Reasoning is tied to appearances, and taking another point of view is hard.

3. Concrete operational, about 7 to 11

   Logic works on real things. The marker is conservation: the same water in a tall glass is no longer more water.

4. Formal operational, about 11 and up

   Reasoning runs on possibilities, hypotheses and what would follow if something were true.

Where it came from

Piaget worked in Geneva from the 1920s and much of the early evidence came from watching his own three children closely and setting them small problems. He published The Origins of Intelligence in Children in 1936, and in English in 1952. With Barbel Inhelder he summed the scheme up in The Psychology of the Child in 1969.

His method was the clinical interview: give a child a task, ask why, and follow the answer. It is why the tasks are so memorable and why the ages attached to them are so soft.

What holds up, and what does not

The sequence is broadly right and the tasks replicate. Children really do fail conservation and then pass it, and the shift is not about knowing more water facts.

The ages are too late, and that is now well established. Infants look longer at impossible events involving hidden objects, months before Piaget's age for object permanence (Baillargeon and DeVos, 1991). The knowledge seems to be there before a child can act on it. Children also pass perspective and conservation tasks earlier when the task is made less confusing. The modern picture is more gradual than four clean steps, and more uneven across different kinds of problem.

What it does not mean

The stages are not a schedule to measure a child against, and a child who passes a task early or late is not ahead or behind. Piaget was describing a route, and the route survives better than his timetable.

Check yourself

Three questions on what is above. Each answer says why.

1. A child says the same water is more water once it is poured into a taller glass. Which stage does that put them in?

   1. Sensorimotor
   2. Preoperational
   3. Concrete operational
   Show the answer

   Answer: B. Failing conservation is the preoperational marker: reasoning follows how the water looks. Passing it is the concrete operational stage.

2. Pick the statement that describes accommodation.

   1. Taking in a fact that fits the model you already have
   2. Changing the model because a fact does not fit it
   3. Forgetting a fact that does not fit
   Show the answer

   Answer: B. Assimilation takes in what fits. Accommodation is the model itself changing, which is where Piaget thought development happened.

3. What did the later looking time experiments change?

   1. The order of the stages
   2. The ages at which the abilities appear
   3. The idea that children build models at all
   Show the answer

   Answer: B. Infants show surprise at impossible hidden object events well before Piaget's age for object permanence. The sequence held up better than the timetable.

Sources

1. Piaget, J. (1936, English edition 1952). The Origins of Intelligence in Children. International Universities Press.
2. Piaget, J., and Inhelder, B. (1969). The Psychology of the Child. Basic Books.
3. Baillargeon, R., and DeVos, J. (1991). Object permanence in young infants: Further evidence. Child Development, 62(6).

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