Knowledge partitioning is a theoretical construct holding that knowledge is not always integrated and homogeneous but may be separated into independent parcels containing mutually contradictory information. Knowledge partitioning has been observed in research on expertise, categorization, and function learning. This article presents a theory of…

It is proposed that many phenomena of human hypothesis testing can be understood in terms of a general positive test strategy. With this strategy, there is a tendency to test cases that are expected to have the property of interest rather than those expected to lack that property. (Author/LMO)

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…