Present a typical conservation task that is used
with children. Pour equal amounts of colored liquid into two identical
containers. Ask one or more students if the amounts are equal, and adjust
the level of liquid if necessary. Pour the liquid from one container to
the container that has a different shape. Again ask the students if both
containers contain the same amount of liquid.
Describe the behavior that is commonly seen in a preoperational child. The child may focus on the level of liquid or the size of the container, but will say that the amount of liquid is no longer equal in the two containers of different shapes. They tend to focus on a single aspect of the situation, such as the different level of liquid or the width of the two containers, and fail to focus on the constancy of the amount of water transferred.
For example,
(a) show the child two clay balls of equal mass;
(b) after the child agrees that they are the same, mash one ball into a "pancake" shape;
(c) ask the child which ball has more clay;
(d) reverse the process by making the "pancake" a "ball" and the "ball" a "pancake" and ask the same questions.
Describe the following experiment: What if I subtract 2 inches from the height of Window B, but add 2 inches to its width? Now which window contains more glass, A or B? Record the students' answers:
Many students will say that the areas of the two
windows are still the same, although they are not. Give a concrete example
with numbers. Say, "To obtain the area of a rectangle or a square, you
multiply the length by the width; in the case of Windows A and B before
the change, both areas are, let's say, 6 inches by 6 inches, or 36 square
inches, but window B is now 8 by 4 inches, or 32 square inches!" Interestingly,
preoperational children, those who fail Piaget's conservation tasks, usually
tend to get this one right!
Then, ask the students: Why do adults tend to get
this problem wrong and preoperational children get it right? What does
this tell us about Piaget's theory, or about how people tend to solve problems?
Some critics of Piaget's believe that Piaget got the results he did because
of the questions he asked, and that if these questions are posed differently
or worded differently, that young children can answer them correctly! This
second demonstration shows that even adults can apply the wrong rules when
solving these types of problems.