devised an instructional intervention, strategy writing, based on expert analyses of problems (see Chi et al., 1981). A strategy was defined for students as a prose paragraph that discussed qualitatively the ‘‘what, why, and how'' of a problem's solution. More specifically, students were told that a strategy should (a) select the principle(s)/concept(s) that could be applied to solve a problem, (b) provide a justification for why the principle(s)/concept(s) could be applied, and (c) describe a procedure for applying the principle(s/concept(s) to generate a solution. (Note that the second component of the strategy is the illusive tacit knowledge described earlier.) As we hope the reader can see, this is nearly identical to our operational definition of CPS provided earlier. Other than this general description of what was meant by strategy, the only other guidance given to students on how to write a good strategy was to tell them to apply the following test to the quality of a strategy they might write: If a student who is stuck solving a problem is provided with a problem''); this problem counted for 25% of the exam grade with the strategy accounting for half of the credit.