  We propose deeper tests of the existence of DM interactions between heavy
particles in $e^+e^-\to t\bar t, ZZ, W^+W^-$ by looking at the effects on final
state polarization. We show that indeed $t$, $W$ and $Z$ polarization are
particularly sensitive to the structure of these interactions, to their
relation with the origin of the masses and to the quantum numbers of the
possibly exchanged dark particles.
