No evidence of quantum brain theory

(Andrew W., PoliSci@Madison, Our place in the universe: Alexander Wendt and

quantum mechanics International Theory (2022), 14 (1), 130–145 doi:10.1017/S1752971921000063)

In chapter 5, he argues that the brain is a quantum computer. Every bit of matter has quantum processes within it, of course. Quantum brain theory goes beyond this to argue that the brain sustains wave functions over macroscopic distances and that they do essential work in computation and thought. Wendt acknowledges that this cuts against the widely held ‘neuron doctrine’, 9 by which neurons are thought to be the smallest structures in the brain necessary to understand thought. He argues for ‘microtubules’ as possible sites of uncollapsed wave functions within neurons. And he acknowledges that ‘the idea has been ignored by most neuroscientists and philosophers of mind’ 10 in part because there is essentially no evidence for it. The obvious objection is that in an environment so warm and full of matter as the brain, wave functions are constantly interacting with other matter and collapsing over quantum distances, and so it is difficult to envision how they could remain in their quantum states long enough to contribute much to thought. Quantum brain theory, therefore, remains a speculative theory in a fringe literature. Nevertheless, Wendt wants us to accept the theory as a plausible candidate because it hasn’t been disproven, reversing the usual burden of truth for new theories in which extraordinary claims require extraordinary evidence.11 He takes this stance primarily because a quantum brain is a necessary building block for the quantum society he depicts later in the book. But for those of us who are not predisposed to believe in such a vision, the burden of proof should be on the new claim, and the logic and evidence for it is quite weak. No one arguing for quantum mechanics when it emerged a hundred years ago had to ask for the benefit of the doubt. Crucial experiments confirmed its predictions again and again. Quantum brain theory has had no such confirmation, and there is no reason to require anything less.