Children’s understanding of floating and sinking: Predictions and explanations tell different stories

The study of children’s knowledge representations of physical principles could benefit from insights in category learning research. The present study used these insights in systematically investigating the development of children’s knowledge representations of buoyancy. Four- to twelve-year-old children (N = 139) were asked to predict buoyancy for different types of objects and to provide explanations for their answers. Three sets of objects differing in appearance were presented: cubes with indistinctive appearance, differing in density, volume and mass (Set 1), cubes made from a distinctive material, wood and metal (Set 2), and well-known objects that are exemplar floaters or sinkers, e.g. a coin and a boat (Set 3). To account for individual differences in knowledge representations, responses on the prediction task were modeled with latent regression analysis. Results showed that children integrated mass and volume in predicting buoyancy of Indistinctive cubes (Set 1), and they integrated mass, volume and material for predicting buoyancy of Material cubes (Set 2). This information integration remained largely implicit because very few children gave explicit explanations of buoyancy that agreed with their predictions. Explanations about buoyancy mostly agreed with simple rules (for Set 1 and 2) or simple facts about exemplars (Set 3). Response strategies in predictions (but not the explanations) showed a clear developmental pattern, such that the way mass and volume were integrated improved with age.