Quantum Structure in Cognition: Why and How Concepts are Entangled

TL;DR

This paper explores how quantum entanglement naturally arises in the combination of concepts within a quantum-inspired cognitive model, supported by experimental violation of Bell's inequalities.

Contribution

It demonstrates that concept combination inherently involves entanglement, revealing a quantum structure in cognition through theoretical modeling and experimental validation.

Findings

Bell's inequalities are violated in concept combination experiments.

Entanglement explains the weights of exemplars in combined concepts.

Quantum formalism models context effects in cognition.

Abstract

One of us has recently elaborated a theory for modelling concepts that uses the state context property (SCoP) formalism, i.e. a generalization of the quantum formalism. This formalism incorporates context into the mathematical structure used to represent a concept, and thereby models how context influences the typicality of a single exemplar and the applicability of a single property of a concept, which provides a solution of the 'Pet-Fish problem' and other difficulties occurring in concept theory. Then, a quantum model has been worked out which reproduces the membership weights of several exemplars of concepts and their combinations. We show in this paper that a further relevant effect appears in a natural way whenever two or more concepts combine, namely, 'entanglement'. The presence of entanglement is explicitly revealed by considering a specific example with two concepts, constructing some Bell's inequalities for this example, testing them in a real experiment with test subjects, and finally proving that Bell's inequalities are violated in this case. We show that the intrinsic and unavoidable character of entanglement can be explained in terms of the weights of the exemplars of the combined concept with respect to the weights of the exemplars of the component concepts.