I find this interesting as well. I havenīt seen this happen in Aikido, although itīs quite possible. I know, as a teacher, that students often learn a bit, then reach a plateau, then dip a bit while their brains organize the new information, then shoot above the previous knowledge mark. After learning some more, the same occurs, a slight drop, then another rise above the previous level. Itīs interesting to see as a graph.