Am I wasting my time as a research assistant?
Many days I will spend 5+ hours on the phone without scheduling a single subject.


I do not think it is unreasonable for someone without any graduate level education to spend 50% of their time doing grunt work in a cognitive neuroscience lab (e.g., scheduling participants, filing paperwork, preparing regulatory reports, cleaning and calibrating equipment, ordering supplies). The fact that so much of your time is spend doing the same type of grunt work and that the cool stuff is limited, means that it sounds like you may be wasting your time.

My suggestion is for you to tell your PI about how you are spending your time and some of the tasks you would like to be involved in. Potentially, there is a happy compromise. Many PIs do not know how long things take.

As for pay and studying for the GRE, those are really personal issues. I cannot imagine it being really beneficial to spend 8+ hours a day studying for the GRE. In general, RAs are paid just enough that they will struggle to make ends meet with rent, car payments, phone payments, and student loans. There is often not much flexibility on the PI side to pay an RA more.