Two stages of skill development are: declarative (facts are interpreted) and procedural (knowledge is embodied in skill procedures). Knowledge compilation moves skills from the declarative to procedural stage in subprocesses of composition, which collapses sequences of productions into single productions, and proceduralization, which embeds…

Skill theory attempts to provide tools for the prediction of developmental sequences in any domain at any point in development. The theory suggests a common framework for integrating developmental analyses of cognitive, social, perceptual/motor skills, and behavioral changes in learning and problem solving. (Author/GK)

This article has three goals: to set forth some general claims about the course of skill acquisition; to discuss a series of counter intuitive predictions derived from the ACT theory; and to review the state of empirical evidence relevant to these predictions. (LMO)