Modeling Human Decision‐Making: An Overview of the Brussels Quantum Approach

We present the essentials of the quantum-theoretic proposal we have developed in a decade of research on the modeling of cognitive phenomena that have resisted traditional modeling techniques by means of classical logical and probabilistic structures, like Boolean, Kolmogorovian and, more generally, set-theoretic structures. We firstly sketch the operational and realistic foundations underlying any representation of cognitive entities, from natural concepts and their combinations, to more complex situations, involving decision making entities and entities of meaning. Then, we sketch the application of the quantum-theoretic approach in Hilbert space to represent combinations of natural concepts, illustrating its success in modeling a wide range of empirical data collected on membership weights of exemplars with respect of pairs of concepts and their conjunction, disjunction and negation. The empirical deviations from classical set-theoretic structures in concept membership judgments (traditionally known as `over- and under extension’) are an example of `fallacies of human reasoning’, and fall under the so-called `human probability judgments’. Other relevant examples of probability errors in human judgments come from decision theory, namely, the `conjunctive and disjunctive fallacies’ observed in Tversky-Kahneman’s Linda-like stories. In this respect, we show that the quantum-theoretic approach in Hilbert space successfully models empirical data, explaining at the same time the conjunction and disjunction fallacies as special cases over- and under extension effects, respectively. Then, we come to decision-making errors and show that the disjunction effect observed in Tversky-Shafir's two-stage gamble and Hawaii story can be explained within the same quantum-theoretic framework. We summarize our findings above, observing that the quantum-theoretic approach also provides a unitary model of human reasoning in which the above mentioned deviations from classicality are naturally explained in terms of quantum effects, contextuality, emergence, entanglement, interference and superposition.