P1.D.3Piagetian research: conservation, egocentrism (three mountains task) and class inclusion

Piaget designed elegant experiments to reveal the limits of children's thinking at each stage. AQA names three: conservation, egocentrism (three mountains) and class inclusion. Knowing the procedure of each is essential.

1. Conservation

Conservation is the understanding that quantity does not change when appearance changes. There are several versions:

• Number conservation: two rows of equal counters; spread one row out. Pre-operational children say the longer row has "more."
• Liquid conservation: pour water from a short, wide glass into a tall, thin glass. Pre-operational children say the tall glass has "more water."
• Mass conservation: roll a ball of clay into a sausage shape. Pre-operational children say the sausage has "more clay."

Piaget's conclusion: pre-operational children cannot decentre — they focus on one perceptual feature (length, height) and ignore the compensating change.

Donaldson's critique (1978). When McGarrigle and Donaldson reframed the conservation task with "Naughty Teddy" who "messes up" the counters, children as young as 4 conserved correctly. The original task may have been confusing because the experimenter's deliberate transformation suggested they expected a different answer.

2. Egocentrism — the Three Mountains Task

A child sat at one side of a model of three mountains (different colours, distinctive features). A doll was placed at another vantage point. The child was shown 10 photographs of the mountains from different angles and asked: "Which photo shows what the doll sees?"

Finding: pre-operational children (4–5) chose photos that showed their own viewpoint. By concrete operational (8–9), most children chose correctly.

Hughes' critique (1975). When the task was re-run with two intersecting walls and a "policeman" looking for a boy, 90% of children aged 3.5 succeeded. Familiar narrative made the task accessible — the original may have measured language and unfamiliarity rather than egocentrism.

3. Class inclusion

Piaget showed children a set of beads: 7 brown wooden, 3 white wooden. He asked: "Are there more brown beads or more wooden beads?" Pre-operational children typically said "more brown" — they could not simultaneously hold the subset (brown) and the superset (wooden) in mind.

Class inclusion requires understanding that a category can include subcategories ("dogs are mammals"). It develops in the concrete-operational stage.

Why these tasks matter

Together they evidence Piaget's claim that pre-operational thought is dominated by perception and centration; concrete-operational thought adds logical operations like reversibility and decentration.

Limitation: subsequent research suggests children fail Piaget's tasks partly because of language, demand characteristics, and task design, not pure cognitive incapacity.