  While filaments are generally interpreted as a dynamic balance between Kerr
focusing and plasma defocusing, the role of the higher-order Kerr effect (HOKE)
is actively debated as a potentially dominant defocusing contribution to
filament stabilization. In a pump-probe experiment supported by numerical
simulations, we demonstrate the transition between two distinct filamentation
regimes at 800\,nm. For long pulses (1.2 ps), the plasma substantially
contributes to filamentation, while this contribution vanishes for short pulses
(70 fs). These results confirm the occurrence, in adequate conditions, of
filamentation driven by the HOKE rather than by plasma.
