uring the pre-operational stage defined by Piaget, a child performs in a characteristic way on tests called conservation experiments . Piaget is famous for these demonstrations. Toconserve in Piaget's terminology is to preserve internally or represent. The conservation experiments all require a child to demonstrate possession of some concept, usually a concept that develops around the ages of 5 to 7.

What does it mean to say a child can conserve something, in Piaget's terminology? What is the classic conservation experiment involving liquid quantity?

One of the classic conservation experiments involves liquid quantity. A child is first shown two short, fat beakers. They are filled with colored water as the child watches. The child is asked to say when the two beakers have the same amount of water in them. If necessary, the experimenter pours a bit of liquid from one to the other until the child agrees that the level of colored water is the same in both beakers.

Next the adult takes a tall, thin beaker and pours colored water from one of the short, fat beakers into one of the tall, thin beakers. The child is asked to compare the tall thin beaker to the short fat one. The experimenter asks, "Which contains more, or do they contain the same amount?" Most children under the age of 6 will point to the tall beaker and say, "This one has more in it." The child is swayed by the perceptual cue of height.

Such a child lacks a conception of the quantity of a liquid. Not having this concept, the child has no way to realize that something stays the same when liquid is poured from one vessel to another. What stays the same? Adults call it liquid quantity. We know what liquid quantity is; we take it for granted. But a child does not yet have this concept or schema.

Some students find it hard to believe that a child could be fooled so easily by appearances at the age of 4 or 5. They go home and try the experiment with a little brother or sister, only to verify Piaget's basic finding. Little children are typically swayed by external appearances.

What were some other conservation experiments by Piaget?

Piaget described numerous conservation experiments. For example, in his conservation of mass experiment, a bit of clay (which Piaget called plasticene) is rolled into a ball. A second ball of clay the same size is shown to the child, who agrees that they are equal. Then one of the balls is rolled between the palms of the adult's hands, forming a sausage shape. "Now does one have more clay in it than the other, or do they still have the same amount of clay in them?" The small child typically points to the sausage shape, which is longer, and claims that it has "more clay in it."

Conservation of area is tested by asking the child whether more ground is covered by the blocks that are spread out or the blocks that are close together. Non-conserving children tend to assume the blocks cover more area when spread out, even though this opens up areas between them.

Placing coins such as pennies on a table tests conservation of number. Seven or eight coins are placed in a row, and a matching series of coins is placed directly below the first one. So there are two equal rows of coins on the table. Now the experimenter spreads out one of the rows so the coins are farther apart. The child is asked whether the two rows of coins still have the same number of coins in them. A small

child who does not yet know how to count will typically claim that the spread-out row has more coins in it.

All the conservation experiments are variations on a theme. The word conservation means preserving something in the face of change. To come up with the correct answer in a conservation experiment, the child must preserve something in his or her head. That "something" is an awareness of quantity, mass, number, area, or some other abstract characteristic of reality. That was Piaget's point. He described himself as studying the construction of reality in the child, which was the subtitle of one of his books.

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