ACT-R

Act-R is a complicated and fascinating thoery of human cognition. The Carnegie Mellon University website has a series of tutorials on the subject as well as an excellent overview of the theory.

"ACT-R is a cognitive architecture: a theory about how human cognition works. On the exterior, ACT-R looks like a programming language; however, its constructs reflect assumptions about human cognition. These assumptions are based on numerous facts derived from psychology experiments."