An effective learning environment is designed to expose student misconceptions because, once explicit, they are available for remediation. How does one design such an environment, and what are the consequences for learning? In a previous study, we demonstrated that a significant revision to the Cognitive Tutor Geometry intelligent tutor had a generally positive effect on the speed of skill mastery (Hausmann & Vuong, 2012). However, the revised version demonstrated a higher error rate for easy skills. We hypothesized that the revised interface reified certain mental steps that students were previously allowed to complete implicitly. Specifically, students are now required to write an expression for the length of the side of a special right triangle before calculating the length. While the error rate for the calculation remained low (1.71%), writing the expression proved to be particularly difficult (13.93%). We contrast the evidence supporting this hypothesis with evidence for other potential explanations.