The author integrates work from cognitive and developmental psychology with studies in writing in order to explain why the quality of student writing sometimes appears to regress to earlier or less proficient levels. Insights from this combined analysis are applied to explain how and why to use specific Writing Across the Curriculum strategies to help students write more clearly, coherently, and correctly. The concepts explained should be of interest to anyone concerned about the quality of student writing, and the strategies discussed should be of use in a variety of disciplines. (Contains 2 footnotes and 5 figures.)