  A large fraction of the world data on both polarized and unpolarized
inclusive $ep$ scattering at large Bjorken $x$ lies in the resonance region
where a correspondence with the deep inelastic regime, known as Bloom and
Gilman's duality, was observed. Recent analyses of the $Q^2$ dependence of the
data show that parton-hadron duality is inconsistent with the twist expansion
at low values of the final state invariant mass. We investigate the nature of
this disagreement, and we interpret its occurrence in terms of contributions
from non partonic degrees of freedom in a preconfinement model.
