Quantum Reality

by Jim Baggott

  We keep going. We can trace the chemical and physical changes that result from the interactions of photons with cone cells in your retina all the way to the stimulation of your visual cortex at the back of your brain. Look all you like, but you will not find the experience of the colour red in any of this chemistry and physics. It is obviously only when this information is somehow synthesized by your visual cortex do you have a conscious experience of a beautiful red rose.

  Just how is this supposed to work? This is the hard problem, as philosopher and cognitive scientist David Chalmers explained:12

  The really hard problem of consciousness is the problem of experience…. When we see, for example, we experience visual sensations: the felt quality of redness, the experience of dark and light, the quality of depth in a visual field. Other experiences go along with perception in different modalities: the sound of a clarinet, the smell of mothballs. Then there are bodily sensations, from pains to orgasms; mental images that are conjured up internally; the felt quality of emotion, and the experience of a stream of conscious thought. What unites all of these states is that there is something it is like to be in them. All of them are states of experience.

  The problem is hard because we not only lack a physical explanation for how this is supposed to happen, we don’t even really know how to state the problem properly.

  Okay. If the ‘how’ problem is too hard, can we at least generate some clues by pondering on where these experiences might be happening?

  The French philosopher René Descartes is rightly regarded as the father of modern philosophy. In his Discourse on Method, first published in 1637, he set out to build a whole new philosophical tradition in which there could be no doubt about the absolute truth of its conclusions. From absolute truth, he argued, we obtain certain knowledge. However, to get at absolute truth, he felt he had no choice but to reject as being absolutely false everything in which he could have the slightest reason for doubt. This meant rejecting all the information about the world that he received through his senses.

  Why? Well, first, he could not completely rule out the possibility that his senses would deceive him from time to time as, for example, through optical illusions or the sleight of hand and mental manipulations involved in magic tricks.13 Second, he could not be certain that his perceptions and experiences were not part of some elaborate dream. Finally, he could not be certain that he was not the victim of a wicked demon or evil genius with the ability to manipulate his sensory inputs to create an entirely false impression of the world around him (just like the machines in The Matrix).

  But he felt that there was at least one thing of which he could be certain. He could be certain that he was a being with a conscious mind that has thoughts. He argued that it would seem contradictory to hold the view that, as a thinking being, he does not exist. Therefore, his own existence was also something about which he could be certain. Cogito ergo sum, he concluded. I think therefore I am.

  The external physical world is vague and uncertain, and may not appear as it really is. But the conscious mind seems very different. Descartes went on to reason that this must mean that the conscious mind is separate and distinct from the physical world and everything in it, including the unthinking machinery of his body, and his brain. Consciousness must be something ‘other’, something unphysical.

  This mind–body dualism (sometimes called Cartesian dualism) is entirely consistent with belief in the soul or spirit. The body is merely a shell, or host, or mechanical device used for giving outward expression and extension to the unphysical thinking substance. It seems reasonably clear that this kind of dualism is what both von Neumann and Wigner had in mind when they identified consciousness as the place (component III) where physical mechanism is no longer applicable, something outside the calculation and therefore the ideal place for the collapse of the wavefunction.

  But to conclude from this that the conscious mind must therefore be unphysical involves a rather bold leap of logic, one that many contemporary philosophers and neuroscientists believe is indefensible. The trouble is that by disconnecting the mind from the brain and making it unphysical we push it beyond the reach of science and make it completely inaccessible. Science simply can’t deal with it. In The Concept of Mind, first published in 1949, the philosopher Gilbert Ryle wrote disparagingly of Cartesian-style mind–body dualism, referring to it as the ‘ghost in the machine’.14 In his 1991 book Consciousness Explained, the philosopher Daniel Dennett argued that ‘accepting dualism is giving up’.15

  Faced with this impasse, the only way to progress is to make some assumptions. We assume that, however it works, consciousness arises as a direct result of the neural chemical and physical processes that take place in the brain. Our experience of a red rose has a neural correlate—it corresponds to the creation of a specific set of chemical and physical states involving a discrete set of neurons located in various parts of the brain. In philosophical terms, this is known as ‘materialism’.

  Neuroscientists have access to a battery of technologies, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), which can probe the workings of the brain in exquisite detail in non-invasive ways. Experiencing something or thinking about something stimulates one or more parts of the brain. As these parts get to work, they draw glucose and oxygen from the bloodstream. An fMRI scan shows where the oxygen is being concentrated, and so which parts of the brain are ‘lighting up’ as a result of some sensory stimulus, thought process, emotional response, or memory. A PET scan makes use of a radioactive marker in the bloodstream but otherwise does much the same thing, though with lower resolution.

  Neuroscience in its modern form was established only in the second half of the past century, and our understanding has come an awfully long way in that relatively short time. But we must once again acknowledge that whilst studying the brain has revealed more and more of the materialist mechanism, it hasn’t yet solved the ‘hard problem’.

  Some neuroscientists are nevertheless convinced that consciousness is to be found in chemical and neurophysiological events, that consciousness is not a ‘thing’ but rather an emergent consequence of a complex set of processes occurring in a developed brain.16

  Grounding consciousness in neuronal activity implies that it is not the exclusive preserve of human beings. In July 2012, a prominent international group of cognitive neuroscientists, neuropharmacologists, neurophysiologists, neuroanatomists, and computational neuroscientists met together at the University of Cambridge in England. After some deliberations, they agreed the Cambridge Declaration on Consciousness, which states:17

  the weight of evidence indicates that humans are not unique in possessing the neurological substrates that generate consciousness. Nonhuman animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates.

  Are cats conscious? The Cambridge Declaration would suggest that they are. Schrödinger’s cat might again be spared the discomfort of being both alive and dead, its fate already decided (by its own consciousness) before you lift the lid of the box, and look. To some extent, this answers Bell’s challenge. You don’t need a PhD to collapse the wavefunction. But you do need to be awake.

  According to the current broad consensus, the human mind is the result of evolutionary selection pressures, driven in Homo sapiens by feedback loops established between an expanding neural capacity, genetic adaptations, and anatomical changes promoting the development of language capability, and the construction of societies. This is the social brain hypothesis. Paleoanthropologists date the specifically human ‘light bulb moment’ to between 40,000 to 50,000 years ago. This is the moment of the Great Leap Forward, or the ‘human revolution’, a flowering of human innovation and creativity involving the transition to what is known as behavioural modernity.

  In this ‘standard model’, consciousness is a natural consequence of the physical, chemical, and biological processes involved in
evolution. Now, the bulk properties of water (freezes at 0°C, boils at 100°C) are consequences of the physical properties of up and down quarks, gluons, and electrons, though we would be very hard pressed to predict the former based on what we currently know about the latter. So consciousness is a (so far unpredicted and unpredictable) consequence of the conventional material content of the Universe which emerges when we connect billions of neurons together to form an extended network in the brain, and then run billions of complex computations on this. Consciousness didn’t somehow ‘pre-exist’.

  But what if the Universe has always contained physical events that are, in some sense, ‘atoms’ of consciousness that existed long before biology? What if one consequence of evolution has then been to assemble these ‘atomic’ events, orchestrate them, and couple them to activity occurring within the neurons in the brain, resulting in what we identify as consciousness? What if the events in question are associated with the distinctly non-computable collapse of the wavefunction? Then we have what Penrose and Stuart Hameroff, professor of anesthesiology at the University of Arizona, have called orchestrated objective reduction, or Orch-OR, a proposal for a quantum basis for consciousness.

  This idea dates back to the early 1990s, and was initially developed separately by Penrose and Hameroff before they chose to combine their efforts in a collaboration. Not surprisingly, Penrose approached the problem from the perspective of mathematics. In his book The Emperor’s New Mind, he argued in favour of a fundamental role for consciousness in the human comprehension of mathematical truth, one that goes beyond computation. ‘We must “see” the truth of a mathematical argument to be convinced of its validity,’ he wrote. ‘This “seeing” is the very essence of consciousness.’18 This is entirely consistent with von Neumann’s assertion that consciousness ‘remains outside of the calculation’.

  We’ve already seen in the previous chapter that, in this same book, Penrose put forward arguments in favour of a role for local mass–energy density and the curvature of spacetime in collapsing the wavefunction, in what was later to become known as Diósi–Penrose theory. However, having convinced himself that consciousness is at heart the result of some kind of non-computable process, and having also proposed a mechanism for the collapse of the wavefunction, he wasn’t yet able to make the connection. What he lacked was a physical mechanism that would allow quantum events somehow to govern or determine brain activity, and thence consciousness:19

  One might speculate, however, that somewhere deep in the brain, cells are to be found of single quantum sensitivity. If this proves to be the case, then quantum mechanics will be significantly involved in brain activity.

  Hameroff knew where to look. With Richard Watt from the University of Arizona’s Department of Electrical Engineering, in 1982 he had hypothesized a role for certain protein polymers called microtubules in processing information in the brain. These structures sit inside all complex cell systems, including neurons.* The polymers self-assemble, allowing the formation of synaptic connections between neurons, and helping to maintain and regulate the strengths of these connections to support cognitive functions. Hameroff and Watt theorized that the polymer subunits (globular proteins called tubulins) undergo coherent excitations, forming patterns which support the processing of information much like transistors in a computer.

  The conventional wisdom is that information processing in the brain is based on switching between synapses. There are, on average, about 1000 synapses per neuron, each capable of 1000 switching operations per second. The average human brain has about one hundred billion neurons, and hence a capacity of about 1017 computational operations per second. But there are 10 million tubulin subunits in every cell, capable of switching a million times faster, producing 1016 operations per second per neuron. If the information processing really does occur here, then this suggests an enhancement in the number of operations per second to 1027, an increase of ten orders of magnitude.

  The tubulin subunits possess two distinct lobes, each consisting of about 450 amino acids. Each subunit can adopt at least two different ‘conformations’—two different arrangements of its atoms in space—with slightly different distributions of electron density which generate weak, long-range, so-called ‘van der Waals’ forces between neighbouring units. These forces are thought to be important in facilitating the switching between conformations, which is the basis of the computational operation.

  From the beginning, Hameroff was convinced of the relationship between microtubules and consciousness, not least because of the efficacy of a wide range of very different anaesthetics in temporarily suspending it. Together with Watt, in 1983 he proposed that the chemical anaesthetic seeps into the neuron, disrupting the van der Waals forces between the tubulin subunits, shutting down the computational operations and hence the consciousness of the patient.

  On reading The Emperor’s New Mind, Hameroff approached Penrose and they agreed to collaborate. By the time of publication of Penrose’s sequel, Shadows of the Mind, in 1994, the Penrose–Hameroff Orch-OR theory was firmly established.

  Each tubulin subunit measures about 8 × 4 × 4 billionths of a metre. These link together in polymeric chains which form columns, and 13 columns wrap around to form a hollow tube—the microtubule. These in turn combine with a network of interlinking filaments to make up the neuron’s physical support structure, called the cytoskeleton.

  The Orch-OR mechanism involves the formation of quantum superpositions of the different tubulin conformations, as depicted in Figure 16a. The subunits interact with their neighbours in a cooperative fashion, enabling the development of extended, coherent superpositions across the microtubule. This is shown as steps 1–6 in Figure 16b, where for clarity the microtubule has been unrolled and flattened out. The individual subunit superpositions are shown as the grey elements in this picture. As the extended superposition builds, it passes a threshold determined by the local mass density (and hence local spacetime curvature) according to the Diósi–Penrose theory. The extended wavefunction collapses and the tubulin subunits revert to their classical states. This is the transition between steps 6 and 7 and, according to the Orch-OR theory, this is where consciousness happens (hence the light bulb). The process then begins all over again.

  Figure 16 The Penrose–Hameroff Orch-OR theory is based on the idea that tubulin subunits in the polymer chains that make up microtubules inside neurons can enter a superposition of different conformational states, (a). The subunits interact with their neighbours, and a coherent superposition develops across the microtubule, shown in (b) as steps 1–6. When the superposition reaches a critical mass density, the wavefunction collapses (steps 6 to 7), contributing to a conscious experience.

  This much simplified description of the mechanism doesn’t really do it justice. But I think you should get the sense that this is all very speculative. It is based on the fusion of ideas from the fringes of quantum physics and neuroscience (and, for that matter, from philosophy). And, unsurprisingly, it has been strongly criticized by both physicists and neuroscientists.

  Perhaps the most obvious issue concerns the sustainability of coherent quantum superpositions over what are very large biomolecular structures. As we saw in Chapter 8, superpositions involving structures intermediate between quantum and classical have been created successfully in the laboratory, including organic molecules containing up to 430 atoms. Whilst it’s fair to say that we do not yet know what the upper limit might be, the larger the system, the more difficult it is to protect it from the effects of environmental decoherence. This is why MAQRO is a space mission.

  But each tubulin subunit is a protein structure containing over ten thousand atoms.20 Microtubules vary in length from about 200 up to 25,000 billionths of a metre. The shorter length implies a polymer column of just 25 subunits, and 13 columns implies a microtubule consisting of 325 subunits in total. The Orch-OR mechanism then calls for a coherent quantum superposition spanning a structure containing on the order of 325,000 atoms
, and which must be sustained for millisecond timescales before collapsing. Contrast this with the macroscopic objects suggested for the MAQRO mission, which are small ‘nanospheres’ with diameters of about 100 billionths of a metre.

  It seems extremely unlikely that a coherent quantum superposition can be sustained in the kind of ‘warm, wet, and noisy’ environment likely to be typical of neurons in a working brain. In 2000, theorist Max Tegmark argued that decoherence timescales on the order of a tenth of a trillionth (10−13) to a hundredth of a millionth of a trillionth (10−20) of a second are more likely in this kind of environment.21

  But, once again, we must never underestimate the power of a realistic interpretation to inspire and motivate interest, consistent with Proposition #4. Despite its very speculative nature, the Penrose–Hameroff Orch-OR theory has many components that are potentially accessible to experiment and arguably makes many testable predictions. In a recent 2014 updating of the theory and review of its status, Hameroff and Penrose examine how 20 predictions they had offered in 1998 have fared in the interim. They drew much comfort from a recent discovery by the research group led by Anirban Bandyopadhyay at the National Institute of Material Sciences in Japan, of memory-switching in a single brain microtubule.22 They concluded that the theory had actually fared rather well, giving a ‘viable scientific proposal aimed at providing an understanding of the phenomenon of consciousness’.23

  Needless to say, the one component of the theory for which there is as yet no empirical evidence is the Diósi–Penrose OR mechanism. For now, any potential role for the non-computable collapse of the wavefunction in facilitating consciousness remains stranded on the beaches of Metaphysical Reality.

  Even if evidence for a connection between quantum mechanics and consciousness can one day be found, Chalmers argues that this will still not solve the hard problem: ‘when it comes to the explanation of experience, quantum processes are in the same boat as any other. The question of why these processes should give rise to experience is entirely unanswered.’24