Weighing the evidence: Children's naive theories of balance affect their exploratory play

In this paper we show that, given identical evidence, children with different naïve theories exhibit different patterns of exploratory play. Karmiloff-Smith & Inhelder (1974) demonstrated that before children develop an adult "Mass Theory " of balance, they entertain a "Center Theory", believing that all objects should be balanced at their geometric center. Younger, "No Theory " children balance blocks by trial and error. In Experiment 1 we let Mass Theorists and Center Theorists play with a block that was weighted off to one side. We then “balanced ” the block on a post either at the block's geometric center or at its center of mass. (Thus evidence that was theory-consistent for a Center Theorist was theory-violating for a Mass Theorist and vice versa.) We also introduced a novel toy (a peg and rings). Children were allowed to play freely for 60 seconds. When the evidence about the balancing block was consistent with the children's theories, they showed a standard novelty preference and played mostly with the novel toy. When the evidence violated children's theories, they preferentially played with the balancing blocks. In Experiment 2, we replicated the design with younger, No-Theory children; they showed a novelty preference regardless of whether the block was balanced in its geometric center or center of mass. These results suggest that children's spontaneous exploratory play is systematically affected by the interaction of their naïve theories and the evidence they observe. We discuss these results in terms of the optimality of children's play