  The explanation presented in [Taichenachev et al, Phys. Rev. A {\bf 61},
011802 (2000)] according to which the electromagnetically induced absorption
(EIA) resonances observed in degenerate two level systems are due to coherence
transfer from the excited to the ground state is experimentally tested in a
Hanle type experiment observing the parametric resonance on the $% D1$ line of
$^{87}$Rb. While EIA occurs in the $F=1\to F^{\prime}=2 $ transition in a cell
containing only $Rb$ vapor, collisions with a buffer gas ($30 torr$ of $Ne$)
cause the sign reversal of this resonance as a consequence of collisional
decoherence of the excited state. A theoretical model in good qualitative
agreement with the experimental results is presented.
