A task in which children have to predict the movement of a balance scale that has weights attached on either side of the fulcrum, and where the weights and their distance to the fulcrum vary. Always predicting the correct movement (which side goes down and which goes up) requires sophisticated knowledge of physics (torque), and children progress through three or four developmental stages with characteristic errors. These stages have been modelled in various computational models, as have the nature of the transitions between them. Much of the original developmental research on this task has been carried out by Robert S. Siegler.
See Computational models, Core concepts, Data-driven processes, Force, Intuitive theory of something, Physical knowledge, Problem solving, Quantitative and qualitative change, Torque, Transition