1. Domain knowledge includes the concepts, facts, and procedures explicitly identified with a particular subject matter; these are generally explicated in school textbooks, class lectures, and demonstrations. This kind of knowledge, although certainly important, provides insufficient clues for many students about how to solve problems and accomplish tasks in a domain. Moreover, when it is learned in isolation from realistic problems contexts and expert problem-solving practices, domain knowledge tends to remain inert in situations for which it is appropriate, even for successful students. And finally, although at least some concepts can be formally described, many of the crucial subtleties of their meaning are best acquired through applying them in a variety of problem situations. Indeed, it is only through encountering them in real problem solving that most students will learn boundary conditions and entailments of much of their domain of knowledge. Examples of domain knowledge in reading are vocabulary, syntax, and phonics rules.
2. Heuristic strategies are generally effective in techniques and approaches for accomplishing tasks that might be regarded as “tricks of the trade”; they don’t always work, but when they do, they are quite helpful. Most heuristics are tacitly acquired by experts through the practice of solving problems; however, there have been noteworthy attempts to address heuristic learning explicitly (Schoenfeld, 1985). For example, a standard heuristic for writing is to plan to rewrite the introduction and, therefore, spend relatively little time crafting it in the first draft. In mathematics, a heuristic for solving problems is to try to find a solution for simple cases and see if the solution generalizes.
3. Control strategies, as the name suggests, control the process of carrying out a task. These are sometimes referred to as “metacognitive” strategies (Palincsar and Brown, 1984; Schoenfeld, 1985). As students acquire more and more heuristics for solving problems, they encounter a new management or control problem: how to select among the possible problem-solving strategies, how to decide when to change strategies, and so on. Control strategies have monitoring, diagnostic, and remedial components; decisions about how to proceed in a task generally depend on an assessment of one’s current state relative to one’s goals, on an analysis of current difficulties, and on the strategies available for dealing with difficulties. For example, a comprehension-monitoring strategy might be to try to state the main point of a section one has just read; if one cannot do so, then one has not understood the text, and it might be best to reread parts of the text. In mathematics, a simple control strategy for solving a complex problem might be to switch to a new part of a problem if one is stuck.
4. Learning strategies are strategies for learning any of the other kinds of content described above. Knowledge about how to learn ranges from general strategies for exploring a new domain to more specific strategies for extending or reconfiguring knowledge in solving problems or carrying out complex tasks. For example, if students want to learn to solve problems better, they need to learn how to relate each step in the example problems worked in the textbooks to the principles discussed in the text (Chi, et al., 1989). If students want to write better, they need to find people to read their writing who can give helpful critiques and explain the reasoning underlying the critiques (most people cannot). They also need to learn to analyze each other’s texts for strengths and weaknesses.