That's true, but I'm not sure it's analogous. In sounds like in the study, by "hard parts" they meant the parts that were hard for the students. So it's relativ

That's true, but I'm not sure it's analogous. In sounds like in the study, by "hard parts" they meant the parts that were hard for the students. So it's relative. There were no universal "hard parts" that were actually easy for some.