Conservation refers to an understanding that a quantity (i.e., liquid, number, mass) remains constant despite arbitrary transformations. In the classic Piagetian conservation of liquid task, children are presented with two identical containers holding equal amounts of liquid. Liquid from one of the containers changes in appearance by being poured into a taller, narrower container. The children are asked to judge the equivalence of the transformed liquid and the liquid that remained in its original container, and to justify their answer. A child who grasps conservation is able to take two dimensions into account simultaneously and therefore understands that the change in the height of the transformed liquid is compensated for by the narrower width. That is, despite changes in appearance, the quantity of liquid remains the same. An understanding of conservation marks the presence of Piaget's concrete operational stage of cognitive development, usually reached between five and seven years of age.
See also: PIAGET, JEAN
Diamond, Nina. "Cognitive Theory." In Benjamin Wolman ed., Handbook of Developmental Psychology. Englewood Cliffs, NJ: Prentice-Hall, 1982.
Donaldson, Margaret. "Conservation: What Is the Question?" British Journal of Psychology 73 (1982):199-207.
Rebecca M. Starr