  The consequences of the short range nature of the nucleon-nucleon
interaction, which forces the spatial part of the nuclear wave function to be
as symmetric as possible, on the pseudo-SU(3) scheme are examined through a
study of the collective deformation parameters beta and gamma in the rare earth
region. It turns out that beyond the middle of each harmonic oscillator shell
possessing an SU(3) subalgebra, the highest weight irreducible representation
(the hw irrep) of SU(3) has to be used, instead of the irrep with the highest
eigenvalue of the second order Casimir operator of SU(3) (the hC irrep), while
in the first half of each shell the two choices are identical. The choice of
the hw irrep predicts a transition from prolate to oblate shapes just below the
upper end of the rare earth region, between the neutron numbers N=114 and 116
in the W, Os, and Pt series of isotopes, in agreement with available
experimental information, while the choice of the hC irrep leads to a prolate
to oblate transition in the middle of the shell, which is not seen
experimentally. The prolate over oblate dominance in the ground states of
even-even nuclei is obtained as a by-product.
