  We extend a quantum model in Hilbert space developed in Aerts (2007a) into a
quantum field theoric model in Fock space for the modeling of the combination
of concepts. Items and concepts are represented by vectors in Fock space and
membership weights of items are modeled by quantum probabilities. We apply this
theory to model the disjunction of concepts and show that the predictions of
our theory for the membership weights of items regarding the disjunction of
concepts match with great accuracy the complete set of results of an experiment
conducted by Hampton (1988b). It are the quantum effects of interference and
superposition of that are at the origin of the effects of overextension and
underextension observed by Hampton as deviations from a classical use of the
disjunction. It is essential for the perfect matches we obtain between the
predictions of the quantum field model and Hampton's experimental data that
items can be in superpositions of `different numbers states' which proves that
the genuine structure of quantum field theory is needed to match predictions
with experimental data.
