This study proposes a knowledge organization facilitating human performance on scientifically relevant recall and problem-solving tasks. This organization is structured hierarchically so as to describe knowledge at different levels of detail; it is also task-adapted so that higher levels include information most important for implementing the intended tasks. The efficacy of this organization was assessed by two experiments, in experiment I, college-level subjects read a text and performed special training tasks to acquire knowledge of a physics topic organized either in the preceding hierarchical, or in a detailed single-level .organization; a third group read the single-level organization twice. In a subsequent test, subjects with the hierarchical organization performed appreciably better on tasks of recall, error correction, and knowledge modification. In experiment 2, subjects acquired knowledge in either of two alternative hierarchical organizations of the same physics topic, but with information dist...