  The question of whether the pseudogap in high $T_c$ cuprates is related to
super conducting precursor effects or to the existence of extrinsic bosonic
massive excitations is investigated on the basis of the Boson-Fermion model.
The characteristic three peak structure of the electronic spectral function and
the temperature dependent Fermi vector derived here are signatures for a two
component scenario which can be tested by ARPES and BIS experiments.
