In a typical non-Scrum environment, a Project (or, Product, maybe) Manager will be the one responsible for project/product success, and so assigns tasks to the members, make sure it gets completed. Gives pressure to the assigned members.
When considering a developer's performance, whether you use Waterfall or Scrum, unless a developer has a very highly professional mindset, there exists a certain amount of pressure (to complete the job) which would make the performance of developer at its highest, I think.
I'm trying to learn Scrum, but cannot figure out what (or who) would be the one giving this pressure to the developers. Or, does Scrum (when ideally practised) trust each developer to control his or herself and do whatever is necessary to optimize their performance, on their own?