Piaget's four stages

1. Piaget said every child passes through four stages of cognitive development: sensori-motor, pre-operational, concrete-operational and formal operational.
2. The stages are invariant, which means every child goes through them in the same fixed order.
3. Piaget also called the stages universal, claiming the same four appear in the same order for children everywhere.
4. No stage can be skipped, because each one is built out of the thinking developed in the stage before it.
5. The shift from one stage to the next is qualitative, so a child in a new stage reasons in a way they could not before.
6. The ages attached to each stage are rough guides, because children reach them at different times.

What happens in each stage

1. Sensori-motor: birth to about two
   1. The baby explores the world through the senses and through movement, by looking, grasping, mouthing and shaking.
   2. Thinking is tied to whatever is physically present, so at first a hidden object is treated as gone.
   3. Object permanence arrives towards the end of the stage, from around eight months, when a baby will search for a toy that has been covered up.
2. Pre-operational: about two to seven
   1. The child can now use language and other symbols, so a stick becomes a sword and a cardboard box becomes a rocket.
   2. Thinking is egocentric, so the child assumes you see the situation exactly as they do.
   3. It is also animistic, so a teddy is treated as though it has feelings.
   4. The child cannot yet conserve, so a change in how something looks convinces them the amount has changed.
3. Concrete-operational: about seven to eleven
   1. The child can now think logically, as long as the problem involves real objects they can picture or handle.
   2. Conservation, reversibility and decentration all arrive, and animism drops away.
   3. Purely abstract or hypothetical problems are still beyond them.
4. Formal operational: about eleven onwards
   1. Thinking becomes abstract, so a problem can be worked through in the head with no objects to handle.
   2. The young person can reason about hypothetical situations and test possibilities in an organised way.

Why the order is fixed

1. Conservation needs two features of a display held in mind at once, so it waits for the concrete-operational stage.
2. Hypothetical reasoning is built on logical reasoning about real objects, so formal operational thinking follows concrete-operational thinking.
3. Piaget put the pace down to biological maturation, so teaching cannot push a child into a stage before they are ready for it.

Turning this into marks

1. When two stages are asked for, give each one an ability of its own rather than the same ability reworded.
2. Use Piaget's own label for the stage, because writing about a five-year-old does not secure the knowledge mark for the pre-operational stage.
3. The mark most often lost is giving the age range instead of the ability that defines the stage.
4. Use the word invariant when a question asks why a stage cannot be skipped, and add that each stage is built on the one before.