What can calculus students like about and learn from a challenging problem they did not understand?

This paper reports on part of a study regarding student learning-experiences and affective pathways in undergraduate calculus tutorials. The following question is pursued in this paper: How do the students' key affective states relate to the type of mathematical discourse conducted in class? We present and discuss two lessons where two similar problems were considered. The lessons were filmed and followed by stimulated recall interviews with nine students. Though the students in both lessons did not understand the solution to the challenging problem, they evaluated the lessons and subsequent learning experiences very differently. We suggest the difference was related to the type of discourse employed by the instructor. The lesson that evoked a negative reaction utilized only an object-level discourse. The lesson that evoked a positive reaction additionally utilized a meta-level discourse. We will call this heuristic-didactic discourse. Implications are drawn.