"being disagreeable-that is, behaving in aggressive, selfish, and manipulative ways" - am I the only one finding this definition incorrect? I think a disagreeable person is one not willing to accept an opinion they find incorrect. None of the attributes they listed seem relevant :) Or maybe I'm just being disagreeable
Agreeableness in the five-factor model (Big Five) doesn't necessarily mean being overly compliant; it can also mean being trustful or altruistic (trust and altruism being two facets of agreeableness).
The study uses five-factor terminology with participants completing the Big Five Inventory (BFI) and some also completing the NEO-PI-R, so those are the definitions to keep in mind here.