Acquisition of cognitive skill.

A framework for skill acquisition is proposed in which there are two major stages in the development of a cognitive skill--a declarative stage in which facts about the skill domain are interpreted and a procedural stage in which the domain knowledge is embodied directly in procedures for performing the skill. This general framework has been instantiated in the ACT system in which facts are encoded in a propositional network and procedures are encoded as productions. Two types of interpretive procedures are described for converting facts in the declarative stage into behavior--general problem-solving procedures and analogy-forming procedures. Knowledge compilation is the process by which the skill transits from the declarative stage to the procedural stage. It consists of the subprocesses of composition which collapses sequences of productions into single productions and proceduralization which embeds factual knowledge into productions. Once proceduralized, further learning processes operate on the skill to make the production more selective in their range of applications. These learning processes include generalization, discrimination, and strengthening of productions. Comparisons are made to similar concepts from past learning theories. It is discussed how these learning mechanisms apply to produce the power law speed-up in processing time with practice. Much of the evidence for this theory of skill acquisition comes from work on acquisition of proof skills in geometry but other evidence is drawn from the literature on automatization, language acquisition, and category formation. (Author)