Piaget's Conservation Experiments

Conservation is the understanding that the quantity of something remains the same even when its appearance changes. Piaget argued that children in the pre-operational stage (aged 2–7) cannot conserve, while children in the concrete operational stage (aged 7–11) can. Conservation is one of the most famous and most studied aspects of Piaget's theory.

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What is Conservation?

Conservation involves understanding that certain properties of objects (such as number, volume, mass, or length) remain unchanged even when the object's appearance is altered, as long as nothing has been added or taken away.

For example:

• If you pour water from a short, wide glass into a tall, thin glass, the amount of water remains the same — even though it looks different
• A pre-operational child will typically say the tall glass has more water because the water level is higher

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Piaget's Conservation Tasks

Piaget developed a series of tasks to test conservation across different dimensions:

Conservation of Number

1. Two identical rows of counters are laid out side by side — the child agrees they have the same number
2. One row is spread out so it is longer
3. The child is asked: "Do they have the same number, or does one have more?"

Pre-operational children say the spread-out row has more — they focus on the length of the row rather than counting the actual number.

Conservation of Volume (Liquid)

1. Two identical glasses are filled with the same amount of liquid — the child agrees they are equal
2. The liquid from one glass is poured into a taller, thinner glass
3. The child is asked: "Do they have the same amount, or does one have more?"

Pre-operational children say the taller glass has more — they focus on the height of the liquid.

Conservation of Mass

1. Two identical balls of clay are shown — the child agrees they have the same amount
2. One ball is rolled into a long sausage shape
3. The child is asked: "Do they have the same amount of clay, or does one have more?"

Pre-operational children say the sausage has more — they focus on the length.

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Conservation Experiment Flow (Liquid Volume)

flowchart TB
    A["Two identical short<br/>wide beakers A + B<br/>same amount of water"] --> B{"Pre-transformation:<br/>’Same or different?’"}
    B -->|Child agrees| C[EQUAL]
    C --> D["Pour B into tall<br/>thin beaker C<br/>in full view of child"]
    D --> E{"Post-transformation:<br/>’Same or different?’"}
    E -->|Pre-operational<br/>2-7 years| F["Tall glass has MORE<br/>centres on height<br/>cannot reverse action"]
    E -->|Concrete operational<br/>7+ years| G["Same amount<br/>uses identity,<br/>compensation,<br/>reversibility"]
    F -.criticised by.-> H["McGarrigle + Donaldson 1974<br/>Naughty Teddy:<br/>72% conserve when<br/>change appears accidental"]

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Why Can't Pre-Operational Children Conserve?

Piaget identified several reasons:

1. Centration

Centration is the tendency to focus on one aspect of a situation while ignoring others. Pre-operational children focus on the most visually striking feature (e.g. the height of the water) and cannot take other dimensions (e.g. width) into account.

2. Irreversibility

Pre-operational children struggle with reversibility — they cannot mentally reverse an action. They do not understand that pouring the water back would return it to its original level.

3. Focus on Appearance

Pre-operational children are dominated by how things look rather than by logical reasoning. If it looks like more, they believe it is more.

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When Conservation Develops

Conservation does not develop all at once — it develops gradually across different dimensions:

Type of Conservation	Approximate Age of Acquisition
Number	6–7 years
Mass/Weight	7–8 years
Volume (liquid)	7–8 years
Length	7–8 years
Area	8–10 years

This gradual development is called horizontal décalage — children acquire conservation at different ages for different tasks, even though the logical principle is the same.

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Criticisms of Piaget's Conservation Experiments

McGarrigle and Donaldson (1974): The Naughty Teddy Study

McGarrigle and Donaldson argued that Piaget's conservation tasks were confusing for young children because the experimenter deliberately changed the display and then asked the same question again. Children may have interpreted this as meaning they should give a different answer.

They designed the "Naughty Teddy" study:

• A "naughty teddy" puppet "accidentally" messed up the display (e.g. pushed the counters closer together)
• When the transformation appeared accidental, more children aged 4–6 showed conservation (72% compared to only 13% in Piaget's original version)

This suggests that Piaget underestimated children's abilities — the way the question was asked influenced the results.

Rose and Blank (1974)

Rose and Blank found that when children were only asked the question once (after the transformation, not before and after), more children gave the correct conservation answer. Asking the same question twice may have implied that the experimenter wanted a different answer.

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Evaluation of Piaget's Conservation Research

Strengths

• Conservation has been replicated thousands of times across different cultures, confirming that younger children generally struggle with conservation
• The concept has had a major influence on education — teachers understand the importance of using concrete materials with younger children
• It provides a clear, testable prediction about cognitive development

Weaknesses

• Piaget may have underestimated children's abilities (McGarrigle and Donaldson, Rose and Blank)
• The tasks may have confused children due to demand characteristics — asking the same question twice implies the answer should change
• Conservation develops gradually (horizontal décalage), which is difficult for the stage theory to explain — if entering a new stage grants a new ability, why does it not apply to all tasks simultaneously?

Exam Tip: When evaluating Piaget's conservation experiments, always refer to McGarrigle and Donaldson's Naughty Teddy study as a key criticism. Explain that the way the task was presented may have confused children, leading Piaget to underestimate their abilities.

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Key Points

• Conservation is the understanding that quantity remains the same despite changes in appearance.
• Pre-operational children (2–7) cannot conserve due to centration and irreversibility.
• Piaget tested conservation of number, volume, mass, and other dimensions.
• Conservation develops gradually (horizontal décalage).
• McGarrigle and Donaldson (1974) suggested Piaget underestimated children's abilities.
• The way questions are asked can influence children's responses.

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Worked study: Piaget (1952) — conservation of liquid volume