The development of probability judgment is explained in terms of working memory, composed of four types of storage operations and three types of processing operations. Age changes in probability judgment were related to changes in frequency retrieval, which stem from changes in constraints on work-space capacity. (Author/RD)

A general theory of how children learn conservation concepts is presented. The acquisition process is described at an abstract level in terms of a rule-sampling system, implying a three-state Markov model with identifiable parameters. Three experiments testing the model's quantitative predictions about conservation learning experiments are…