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Preschoolers' reasoning about density: will it float?

Density is a complex concept found to appear late in development. However, density has a readily apparent empirical consequence--buoyancy. Early scientific understanding of density arose through Archimedes' discovery of water displacement as a function of density, and young children have experience playing with objects in water. Therefore, a buoyancy prediction task was developed in order to access preschoolers' early understanding of density. 3-5-year-old children from 2 preschool classes, as well as adults, made buoyancy predictions for a set of objects that varied systematically in density, weight, and volume. 4-5-year-olds (from the older class) and adults were shown to demonstrate similar patterns in their judgments. Objects much more or much less dense than water were more accurately judged than objects with densities closer to the density of water. Weight and volume were found to "interfere" in these judgments in systematic ways for the older class of children and the adults. Children in the younger class (3-year-olds) showed a mean proportion correct performance of .53; they all passed a pretest, however, and no child refused to make judgments.