Thresholds Are Troublesome. Few new ideas in the ongoing inquiry into effective teaching and learning have generated as much productive discussion as the idea of "threshold concepts" and its older sister, "troublesome knowledge." Another name might be bottlenecks. Threshold concepts are “portals” or gateways to transformative educational development (Meyer & Land, 2003; Trafford, 2008), and “going through” this portal leads to significant and important outcomes for the student. To promote deeper learning, faculty should identify key threshold concepts in their disciplines and assist their students in mastering those concepts.