This research uses the Geometry Tutor computer assisted instruction system as an environment to study skill acquisition. A particular model of skill learning, called ACT*, is investigated in detail in three ways. 1) Student performance data with the Geometry Tutor are examined and analysed. 2) Variations of the Geometry Tutor and their effects on learning are studied. 3) A computer simulator of the ACT* theory is interfaced to the Geometry Tutor and used to model a human student's learning process. The importance of this research is that computer supported environments for learning are vital to future science and engineering education. These computer teaching systems must be rationally designed from solid experience and theoretical modeling of how student performance can be optimized.
