  We observe spontaneously driven non-ground state polariton condensation in
GaAs pillar microcavities under non-resonant optical excitation. We identify a
regime where the interplay of exciton-exciton and pair polariton scattering can
lead to mode switching from non-ground state to ground state polariton
condensation. A simple kinematic model satisfactorily describes the observed
mode switching as each of the above scattering mechanisms becomes prevalent at
different carrier densities.
