  While convective flows are implicated in many granular segregation processes,
the associated particle-scale rearrangements are not well understood. A
three-dimensional bidisperse mixture segregates under steady shear, but the
cyclically driven system either remains mixed or segregates slowly. Individual
grain motion shows no signs of particle-scale segregation dynamics that precede
bulk segregation. Instead, we find that the transition from non-segregating to
segregating flow is accompanied by significantly less reversible particle
trajectories, and the emergence of a convective flow field.
