Although reattribution training has been shown to be very useful in improving learning, researchers disagree on what mediates the effects. As to the possible mediating factors, the prominent theories suggest factors such as expectations, notions of intelligence, self-efficacy or anxiety. However, this article proposes an alternative mediating theory, based on the analysis of actual attributions made by the students. The quantitative portion of the study revealed that suggestion, positive messages, functioned just like interventions used in reattribution training to improve the students' self-concept. The analysis of attribution showed that suggestion seemed to improve self-concept through changing attribution patterns. More specifically, suggestion was effective for some students by reducing internal attributions, which can have a negative impact on learning. On the other hand, suggestion did not function positively for students who had relatively serious learning difficulties. Rather than the factors proposed so far, this study showed the importance of self-concept as a mediating factor.