Monday, June 29, 2015

Quantum mental processes?

One of the pleasant aspects of a long career in philosophy is the occasional experience of a genuinely novel approach to familiar problems. Sometimes one's reaction is skeptical at first -- "that's a crazy idea!". And sometimes the approach turns out to have genuine promise. I've had that experience of moving from profound doubt to appreciation several times over the years, and it is an uplifting learning experience. (Most recently, I've made that progression with respect to some of the ideas of assemblage and actor-network theory advanced by thinkers such as Bruno Latour; link, link.)

I'm having that experience of unexpected dissonance as I begin to read Alexander Wendt's Quantum Mind and Social Science: Unifying Physical and Social Ontology. Wendt's book addresses many of the issues with which philosophers of social science have grappled for decades. But Wendt suggests a fundamental switch in the way that we think of the relation between the human sciences and the natural world. He suggests that an emerging paradigm of research on consciousness, advanced by Giuseppi Vitiello, John Eccles, Roger Penrose, Henry Stapp, and others, may have important implications for our understanding of the social world as well. This is the field of "quantum neuropsychology" -- the body of theory that maintains that puzzles surrounding the mind-body problem may be resolved by examining the workings of quantum behavior in the central nervous system. I'm not sure which category to put the idea of quantum consciousness yet, but it's interesting enough to pursue further.

The familiar problem in this case is the relation between the mental and the physical. Like all physicalists, I work on the assumption that mental phenomena are embodied in the physical infrastructure of the central nervous system, and that the central nervous system works according to familiar principles of electrochemistry. Thought and consciousness are somehow the "emergent" result of the workings of the complex physical structure of the brain (in a safe and bounded sense of emergence). The novel approach is the idea that somehow quantum physics may play a strikingly different role in this topic than ever had been imagined. Theorists in the field of quantum consciousness speculate that perhaps the peculiar characteristics of quantum events at the sub-atomic level (e.g. quantum randomness, complementary, entanglement) are close enough to the action of neural networks that they serve to give a neural structure radically different properties from those expected by a classical-physics view of the brain. (This idea isn't precisely new; when I was an undergraduate in the 1960s it was sometimes speculated that freedom of the will was possible because of the indeterminacy created by quantum physics. But this wasn't a very compelling idea.)

Wendt's further contribution is to immerse himself in some of this work, and then to formulate the question of how these perspectives on intentionality and mentality might affect key topics in the philosophy of society. For example, how do the longstanding concepts of structure and agency look when we begin with a quantum perspective on mental activity?

A good place to start in preparing to read Wendt's book is Harald Atmanspacher's excellent article in the Stanford Encyclopedia of Philosophy (link). Atmanspacher organizes his treatment into three large areas of application of quantum physics to the problem of consciousness: metaphorical applications of the concepts of quantum physics; applications of the current state of knowledge in quantum physics; and applications of possible future advances in knowledge in quantum physics.
Among these [status quo] approaches, the one with the longest history was initiated by von Neumann in the 1930s.... It can be roughly characterized as the proposal to consider intentional conscious acts as intrinsically correlated with physical state reductions. (13)
A physical state reduction is the event that occurs when a quantum probability field resolves into a discrete particle or event upon having been measured. Some theorists (e.g. Henry Stapp) speculate that conscious human intention may influence the physical state reduction -- thus a "mental" event causes a "physical" event. And some process along these lines is applied to the "activation" of a neuronal assembly:
The activation of a neuronal assembly is necessary to make the encoded content consciously accessible. This activation is considered to be initiated by external stimuli. Unless the assembly is activated, its content remains unconscious, unaccessed memory. (20)
Also of interest in Atmanspacher's account is the idea of emergence: are mental phenomena emergent from physical phenomena, and in what sense? Atmanspacher specifies a clear but strong definition of emergence, and considers whether mental phenomena are emergent in this sense:
Mental states and/or properties can be considered as emergent if the material brain is not necessary or not sufficient to explore and understand them. (6)
This is a strong conception in a very specific way; it specifies that material facts are not sufficient to explain "emergent" mental properties. This implies that we need to know some additional facts beyond facts about the material brain in order to explain mental states; and it is natural to ask what the nature of those additional facts might be.

The reason this collection of ideas is initially shocking to me is the difference in scale between the sub-atomic level and macro-scale entities and events. There is something spooky about postulating causal links across that range of scales. It would be wholly crazy to speculate that we need to invoke the mathematics and theories of quantum physics to explain billiards. It is pretty well agreed by physicists that quantum mechanics reduces to Newtonian physics at this scale. Even though the component pieces of a billiard ball are quantum entities with peculiar properties, as an ensemble of 10^25 of these particles the behavior of the ball is safely classical. The peculiarities of the quantum level wash out for systems with multiple Avogadro's numbers of particles through the reliable workings of statistical mechanics. And the intuitions of most people comfortable with physics would lead them to assume that neurons are subject to the same independence; the scale of activity of a neuron (both spatial and temporal) is orders of magnitude too large to reflect quantum effects. (Sorry, Schrodinger's cat!)

Charles Seife reports a set of fundamental physical computations conducted by Max Tegmark intended to demonstrate this in a recent article in Science Magazine, "Cold Numbers Unmake the Quantum Mind" (link). Tegmark's analysis focuses on the speculations offered by Penrose and others on the possible quantum behavior of "microtubules." Tegmark purports to demonstrate that the time and space scales of quantum effects are too short by orders of magnitude to account for the neural mechanisms that can be observed (link). Here is Tegmark's abstract:
Based on a calculation of neural decoherence rates, we argue that the degrees of freedom of the human brain that relate to cognitive processes should be thought of as a classical rather than quantum system, i.e., that there is nothing fundamentally wrong with the current classical approach to neural network simulations. We find that the decoherence time scales (∼10^−13–10^−20s) are typically much shorter than the relevant dynamical time scales (∼10^−3–10^−1s), both for regular neuron firing and for kinklike polarization excitations in microtubules. This conclusion disagrees with suggestions by Penrose and others that the brain acts as a quantum computer, and that quantum coherence is related to consciousness in a fundamental way. (link)
I am grateful to Atmanspacher for providing such a clear and logical presentation of some of the main ideas of quantum consciousness; but I continue to find myself sceptical. There is a risk in this field to succumb to the temptation towards unbounded speculation: "Maybe if X's could influence Y's, then we could explain Z" without any knowledge of how X, Y, and Z are related through causal pathways. And the field seems sometimes to be prey to this impulse: "If quantum events were partially mental, then perhaps mental events could influence quantum states (and from there influence macro-scale effects)."

In an upcoming post I'll look closely at what Alex Wendt makes of this body of theory in application to the level of social behavior and structure.

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