  We present modeling for conceptual combinations which uses the mathematical
formalism of quantum theory. Our model faithfully describes a large amount of
experimental data collected by different scholars on concept conjunctions and
disjunctions. Furthermore, our approach sheds a new light on long standing
drawbacks connected with vagueness, or fuzziness, of concepts, and puts forward
a completely novel possible solution to the 'combination problem' in concept
theory. Additionally, we introduce an explanation for the occurrence of quantum
structures in the mechanisms and dynamics of concepts and, more generally, in
cognitive and decision processes, according to which human thought is a well
structured superposition of a 'logical thought' and a 'conceptual thought', and
the latter usually prevails over the former, at variance with some widespread
beliefs
