> ACT-R argues that we have two different memory systems: declarative and procedural.

> The declarative system includes all your memories of events, facts, ideas and experiences. Everything you consciously experience is part of this system. It contains both your direct sensory experience and your knowledge of abstract concepts.

> The procedural system consists of everything you can do. It includes both motor skills, like tying a shoelace or typing on a keyboard, and mental skills, like adding up numbers or writing an email.

> ACT-R explains complex skills as an ongoing interaction between these two systems.