  We analyse in this paper the data collected in a set of experiments performed
on human subjects on the combination of natural concepts. We investigate the
mutual influence of conceptual conjunction and negation by measuring the
membership weights of a list of exemplars with respect to two concepts, e.g.,
'Fruits' and 'Vegetables', and their conjunction 'Fruits And Vegetables', but
also their conjunction when one or both concepts are negated, namely, 'Fruits
And Not Vegetables', 'Not Fruits And Vegetables' and 'Not Fruits And Not
Vegetables'. Our findings sharpen existing analysis on conceptual combinations,
revealing systematic and remarkable deviations from classical (fuzzy set) logic
and probability theory. And, more important, our results give further
considerable evidence to the validity of our quantum-theoretic framework for
the combination of two concepts. Indeed, the representation of conceptual
negation naturally arises from the general assumptions of our two-sector Fock
space model, and this representation faithfully agrees with the collected data.
In addition, we find a further significant deviation and a priori unexpected
from classicality, which can exactly be explained by assuming that human
reasoning is the superposition of an 'emergent reasoning' and a 'logical
reasoning', and that these two processes can be successfully represented in a
Fock space algebraic structure.
