This study used a pretest-posttest design to explore the scoring by female preservice teachers (n=25) of student responses to a pattern problem. The treatment consisted of a cooperative activity that required the preservice teachers to assign scores to a rubric intended to enhance careful attention to student reasoning expressed in written explanations. On the posttest, the majority of preservice teachers elevated their scores for written explanations that demonstrated understanding. However, this did not prove sufficient to dissuade some from giving higher scores to correct answers paired with explanation that did not demonstrate understanding.