Kirschner et al. cited the results of Patel, Groen, and Nor- tha man's(993) research. In this study, students from very different universities with different entering characteristics were compared(and indeed there is a self-selection bias in most studies of PBL). They were compared at a single time on Van a single task, but the PBL students did indeed transfer the stud hypothesis-driven reasoning strategy they were taught to new with problems whereas students in a traditional curriculum did not in use this reasoning strategy. The PBL students were also more on likely to make errors. But a close examination of these results reveals that although the PBL students made more errors, Sing they also created more elaborated explanations compared to the sparse explanations of students in the traditional curriculum.