That's my experience too. There are those who want to get a degree with the least amount of work and don't really find the topic interesting. And then there are those who will discuss it and debate it before/after class, etc.
Good test to tell them apart: if the lecturer mistakenly starts to talk about stuff that he already said in the last lecture (i.e. mistakenly doing the last one again), the first group will be happy and silent because there will be less stuff to learn for the test. The second group will tell the lecturer because they want to learn. This is then often mistaken by the first kind of people as trying to please the professor or "siding" with the prof instead of the fellow students. Because they think in a school-mindset.
Good test to tell them apart: if the lecturer mistakenly starts to talk about stuff that he already said in the last lecture (i.e. mistakenly doing the last one again), the first group will be happy and silent because there will be less stuff to learn for the test. The second group will tell the lecturer because they want to learn. This is then often mistaken by the first kind of people as trying to please the professor or "siding" with the prof instead of the fellow students. Because they think in a school-mindset.