We trace the development of azimuthal anisotropy (nu(n), n = 2, 3) via parton-parton collision history in two transport models. The parton nu(n) is studied as a function of the number of collisions of each parton in Au + Au and d + Au collisions at root s(NN) = 200 GeV. It is found that the majority of nu(n) comes from the anisotropic escape probability of partons, with no fundamental difference at low and high transverse momenta. The contribution to nu(n) from hydrodynamic-type collective flow is found to be small. Only when the parton-parton cross-section is set unrealistically large does th...
