The quantum mind or quantum consciousness hypothesis proposes that classical mechanics cannot explain consciousness. It states quantum mechanical phenomena, such as quantum entanglement and superposition, may play an important part in the brain's function and could form the basis of an explanation of consciousness. It is not a single theory, but rather a collection of distinct ideas forming a hypothesis.
A few theoretical physicists have argued classical physics is intrinsically incapable of explaining the holistic aspects of consciousness, whereas quantum mechanics can. The idea that quantum theory has something to do with the workings of the mind go back to Eugene Wigner. He assumed the wave function collapses due to its interaction with consciousness. Physicist Freeman Dyson argued that "mind, as manifested by the capacity to make choices, is to some extent inherent in every electron." However, most contemporary physicists and philosophers consider these arguments to be unconvincing. Physicist Victor Stenger characterized quantum consciousness as a "myth" having "no scientific basis" that "should take its place along with gods, unicorns and dragons."
The philosopher David Chalmers has argued against quantum consciousness. He has instead discussed how quantum mechanics may relate to dualistic consciousness. Chalmers is skeptical of the ability of any new physics to resolve the hard problem of consciousness.
Description of main quantum mind approaches
David Bohm viewed quantum theory and relativity contradict one another. The contradiction implied there existed a more fundamental level in the physical universe. He claimed both quantum theory and relativity pointed towards this deeper theory, which he formulated in terms of a quantum field theory. This more fundamental level was proposed to represent an undivided wholeness and an implicate order, from which arises the explicate order of the universe as we experience it.
Bohm proposed implicate order applies both to matter and consciousness and suggested it could explain the relationship between them. Mind and matter are seen as projections into our explicate order from the underlying reality of the implicate order. Bohm claims that when we look at the matter in space, we can see nothing in these concepts that helps us to understand consciousness.
In trying to describe the nature of consciousness, Bohm discussed the experience of listening to music. He believed the feeling of movement and change that make up our experience of music derives from both the immediate past and the present both being held in the brain together. The notes from the past are seen as transformations rather than memories. The notes that were implicate in the immediate past are seen as becoming explicate in the present. Bohm viewed this as consciousness emerging from the implicate order.
Bohm saw the movement, change or flow, and the coherence of experiences, such as listening to music, as a manifestation of the implicate order. He claimed to derive evidence for this from the work of Jean Piaget in studying infants. He stated these studies show that young children have to learn about time and space not because they are part of the explicate order; rather, they have a "hard-wired" understanding of movement because it is part of the implicate order. He compared this "hard-wiring" to Chomsky's theory that grammar is "hard-wired" into young human brains.
A major weakness to Bohm's hypothesis is verification. In his writings, Bohm never proposed any specific means by which the propositions could be tested or falsified, nor a neural mechanism through which his "implicate order" could emerge in a way relevant to consciousness. Bohm did, however, collaborate on Karl Pribram's holonomic brain theory as a model of quantum consciousness.
Roger Penrose and Stuart Hameroff
Theoretical physicist Roger Penrose and anaesthesiologist Stuart Hameroff collaborated to produce the theory known as Orchestrated Objective Reduction (Orch-OR). Penrose and Hameroff initially developed their ideas separately and only later collaborated to produce Orch-OR in the early 1990s. The theory was reviewed and updated by the original authors in late 2013.
Penrose's controversial argument stemmed from Gödel's incompleteness theorems. In Penrose's first book on consciousness, The Emperor's New Mind (1989), he argued that while a formal proof system cannot prove its own inconsistency, Gödel unprovable results are provable by human mathematicians. In the book, he took this disparity to mean that human mathematicians are not describable as formal proof systems and are not running a computable algorithm.
Penrose determined wave function collapse was the only possible physical basis for a non-computable process. Dissatisfied with its randomness, Penrose proposed a new form of wave function collapse that occurred in isolation and called it objective reduction. He suggested each quantum superposition has its own piece of spacetime curvature and when these become separated by more than one Planck length they become unstable and collapse. Penrose suggested that objective reduction represented neither randomness nor algorithmic processing but instead a non-computable influence in spacetime geometry from which mathematical understanding and, by later extension, consciousness derived.
Originally, Penrose lacked a detailed proposal for how quantum processing could be implemented in the brain. However, Hameroff read Penrose's work and suggested that microtubules would be suitable candidates. Microtubules are composed of tubulin protein dimer subunits. The tubulin dimers each have hydrophobic pockets that are 8 nm apart and which may contain delocalized pi electrons. Tubulins have other smaller non-polar regions that contain pi electron-rich indole rings separated by only about 2 nm. Hameroff proposed that these electrons are close enough to become quantum entangled. Hameroff originally suggested the tubulin-subunit electrons would form a Bose–Einstein condensate, but this was discredited. He then proposed a Frohlich condensate, a hypothetical coherent oscillation of dipolar molecules. However, this too has been experimentally discredited.
Furthermore, he proposed that condensates in one neuron could extend to many others via gap junctions between neurons forming a macroscopic quantum feature across an extended area of the brain. When the wave function of this extended condensate collapsed, it was suggested to non-computationally access mathematical understanding and ultimately conscious experience which are hypothetically embedded in the geometry of spacetime.
However, Orch-OR made numerous false biological predictions, and is considered to be an extremely poor model of brain physiology. The proposed predominance of 'A' lattice microtubules, more suitable for information processing, was falsified by Kikkawa et al., who showed all in vivo microtubules have a 'B' lattice and a seam. The proposed existence of gap junctions between neurons and glial cells was also falsified. Orch-OR predicted that microtubule coherence reaches the synapses via dendritic lamellar bodies (DLBs), however De Zeeuw et al. proved this impossible, by showing that DLBs are located micrometers away from gap junctions.
In January 2014, Hameroff and Penrose announced the discovery of quantum vibrations in microtubules by Anirban Bandyopadhyay of the National Institute for Materials Science in Japan in March 2013 confirms the hypothesis of the Orch-OR theory.
Umezawa, Vitiello, Freeman
Hiroomi Umezawa and collaborators proposed a quantum field theory of memory storage. Giuseppe Vitiello and Walter Freeman have proposed a dialog model of the mind. This dialog takes place between the classical and the quantum parts of the brain. Their quantum field theory models of brain dynamics are fundamentally different from the Penrose-Hameroff theory.
Karl Pribram's holonomic brain theory (quantum holography) invoked quantum mechanics to explain higher order processing by the mind. He argued the holonomic model solved the binding problem. Pribram collaborated with Bohm in his work on the quantum approaches to mind and he provided evidence on how much of the processing in the brain was done in wholes. He proposed that ordered water at dendritic membrane surfaces might operate by structuring Einstein-Bore condensation supporting quantum dynamics.
Although Subhash Kak's work is not directly related to that of Pribram, he likewise proposes the physical substratum to neural networks has a quantum basis, but he asserts that the quantum mind will still have machine-like limitations. He points to a role for quantum theory in the distinction between machine intelligence and biological intelligence, but that in itself cannot explain all aspects of consciousness.
Henry Stapp favors the idea that quantum waves are reduced only when they interact with consciousness. He argues from the Orthodox Quantum Mechanics of John von Neumann that the quantum state collapses when the observer selects one among the alternative quantum possibilities as a basis for future action. The collapse, therefore, takes place in the expectation that the observer associated with the state.
His theory of how mind may interact with matter via quantum processes in the brain differs from that of Penrose and Hameroff.
Criticism by Max Tegmark
The main argument against the quantum mind proposition is that quantum states in the brain would decohere before they reached a spatial or temporal scale at which they could be useful for neural processing, although in photosynthetic organisms quantum coherence is involved in the efficient transfer of energy, within the timescales calculated by Quantum biology. This argument was elaborated by the physicist, Max Tegmark. Based on his calculations, Tegmark concluded that quantum systems in the brain decohere at sub-picosecond timescales commonly assumed to be too short to control brain function.
- Bohm interpretation of quantum mechanics
- Electromagnetic theories of consciousness
- Evolutionary neuroscience
- Hameroff-Penrose Orchestrated Objective Reduction
- Hard problem of consciousness
- Holonomic brain theory
- Mechanism (philosophy)
- Quantum cognition
- Theory of mind
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