Does Quantum Theory Explain Consciousness?

astroengine writes "Quantum theory is often seen as the root cause of unrelated, mysterious phenomena. Take consciousness for example. British physicist Roger Penrose recently argued 'that we will need to invoke 'new physics and exotic biological structures': rewriting quantum theory to make sense of consciousness.' But why do this, especially as there is no apparent causal link between quantum mechanics and the conscious mind? There appears to be a very basic logical fallacy here that even the most prominent physicists seem to be making."

Comments

Re:Quantum Theory is not relevant

[MoellerPlesset2]

There is no reason to think that quantum physics has anything to do with the nature of conciousness. It is not useful to explain free will, or the illusion of free will, of the qualia of objects, or the steadyness of perception on a background of constantly varying spike rates in the brain.

Quantum chemist here (my username's a hint at that), and I couldn't agree more. I fight against this nonsense all the time.. You'd think that if there was anything to it, we'd be all over it - since explaining chemistry and biochemistry in terms of quantum mechanics is exactly what we do. But nope, I don't know anybody in the field who thinks those ideas have any merit whatsoever. (And let's just point out that as merited a guy Penrose is, he's not a quantum chemist, and more a mathematician than a physicist. His main area of expertise is topology, which has applications in cosmology but is totally unrelated to this area)

It breaks down like this: Electrons in atoms and molecules behave entirely quantum-mechanically. It's why QM was invented in the first place. Since chemical properties are the result of how the electrons behave, all of chemistry is intrinsically quantum-mechanical in some sense.

However: Molecules as a whole do not act quantum-mechanically. They move about according to classical mechanics - and that's how we model them physically too. Because once things get as heavy as an atomic nucleus (save for hydrogen, under some circumstances), their quantum 'uncertainty' in position etc is so small that it's chemically insignificant. So you need QM to describe how two atoms are bonded, but classical mech does a good job of describing how the molecules as a whole bounce around.

So the question is: Are there 'non-trivial' quantum effects in biology? I.e. ones that aren't explainable in terms of 'ordinary' chemistry (which is still ultimately quantum-mechanical). There are a few examples, such as magnetoreception in birds, and energy transfer during some photosynthetic processes. But: despite a lot of the hype surrounding them, these things are still dealing with individual, sub-atomic particles. They don't cast any doubt on 'conventional wisdom' that QM phenomena don't happen at the biological scale. There's nothing in the cell that depends on the actions of a single small molecule, or a single chemical reaction, or anything that's small enough to act quantum-mechanically.

The physics here doesn't make sense (Penrose's ideas in particular don't even hinge on established QM, but rather his own speculative ideas about quantum gravity.. of all things), we have every reason to believe you wouldn't have quantum phenomena at that scale in that environment, and no reason to believe otherwise. The chemistry doesn't make sense, as there's basically nothing hitherto found in biochemistry that doesn't fit into established chemistry. (Which isn't to say biochem hasn't expanded the boundaries of established chemistry, but it hasn't changed the foundations at all) And the biology doesn't really make sense, as cells are not built anything like Geiger counters, sitting in a labile state waiting for a single sub-atomic event to trigger them.

Finally, the philosophy doesn't really add up either. The quantum-consciousness people seem to have an agenda along the lines of 1) QM is non-deterministic 2) If the brain's higher functions rely directly on QM processes, then the brain is non-deterministic 3) That nondeterminism means we have free will.
Little of that makes sense to me. (1) is in fact a matter of which interpretation of QM you choose, and ultimately a question of metaphysics, since any non-deterministic theory could be postulated to be the result of a deterministic underlying 'reality' (as is the case with the Bohm interpretation of QM), or vice-versa. (2) is unwarranted speculation and (3) especially doesn't make much sense to me, since the philosophical question of 'free will' tends to hinge on whet

Re:Recently?

[divisionbyzero]

Indeed, I waded though The Emperors New Mind when it was first published and was very disappointed. As far as I could tell, the argument was something along the lines of "consciousness is mysterious and complex and hopefully non-deterministic. Quantum effects are mysterious and complex and non deterministic. Consciousness is probably a quantum-based phenomenon then".

So I went back to reading Dennett and Hoftstadter.

Then you didn't understand it. His argument was more like: "Human are capable of recognizing when an algorithm will halt (or not); computers are not; therefore thought cannot be reduced to computation". It has nothing to do with the non-deterministic nature of quantum mechanics because even non-deterministic outcomes are computable. His speculation about consciousness and quantum mechanics is based on an analogy between the "collapse of the waveform" and thought. Even though the analogy is suggestive, according to Penrose, quantum mechanics cannot fully explain consciousness (because of consciousness's supposed non-computability) and to the extent that it cannot quantum mechanics is incomplete. It's still a crap argument but it's a hell of a lot better than your caricature. Dennett and Hoftstadter are even worse in many ways. They, like Penrose, are stuck on artifacts of theory. Stick with people that know how the brain actually works, like Edelman.

Re:Quantum Theory is not relevant

[mbone]

1) QM is non-deterministic

(1) is in fact a matter of which interpretation of QM you choose, and ultimately a question of metaphysics, since any non-deterministic theory could be postulated to be the result of a deterministic underlying 'reality' (as is the case with the Bohm interpretation of QM), or vice-versa.

Uh, not so easy. The whole point of the Bell's Theorem tests is that QM is not reducible to a local deterministic theory. Bohm's theory is deterministic, but non-local, which means that it is not causal. So, chose your poison. You can't have it all; QM is not just a normal classical theory hiding behind some measurement weirdness.

*David* Chalmers, Stu Hameroff, Hard Problems

[billstewart]

Tall Aussie guy, long hair, wears leather jackets, sings a mean Zombie Blues*. Chalmers, who's a philosopher, and Stu Hameroff, an anesthesiologist, started a series of conferences at the University of Arizona on "Towards a Science of Consciousness" a decade or two ago; they alternate between Tucson and Somewhere-outside-North-America, and attract a mixed crowd of neuroscientists, consciousness researchers, philosophers who talk about phenomenology, FMRI imagers, tourists (e.g. me), and a few newagey people and random cranks. A few years ago, there were two "Science and Consciousness" conferences in Arizona around the same time - the scientific one in Tucson, and the Deepak Chopra one in Phoenix**.

Hameroff's done work with Penrose on things like quantum effects in microtubules (which are brain cell parts that are small enough to actually have quantum activity going on, though it's a very long step from saying "quantum noise might be affecting chemical reactions a bit" to "Woo-woo! Consciousness is, like, Quantum, man!". I can't say I really understand Stu's arguments about the connections, because while I know a certain amount of quantum physics and biology and philosophy, I don't do neurology or brain cell structures or phenomenology, so the couple of conferences I got to were interesting and a very steep learning curve.

From one perspective, either the world, and therefore consciousness, are entirely deterministic, or else they're not. (Deterministic doesn't mean calculable - Heisenberg among others make it very clear that you can't really simulate the universe using machinery smaller than the universe - but from a philosophical standpoint it doesn't matter if humans can predict what you're doing to do, it just matters whether you've got free will about it.) If you'd like things to be non-deterministic, physics doesn't give you very many ways to hook that into the world, and you're pretty much stuck with quantum mechanics.*** Does that mean that quantum entanglement is involved in any of the processes, particularly between neurons that aren't directly adjacent to each other? Not necessarily (IMHO, probably not.) Does it mean that a non-physical spirit can grab onto some molecules and shake them around in ways that translate up to conscious thoughts, or does it just mean that the chemistry's a bit noisier because God's playing dice with the Universe but your consciousness is still fundamentally a materialist process?

* "Zombie" is a term of art, referring to a hypothetical person or machine that reacts externally as if it were conscious, but doesn't actually perceive qualia the way conscious beings claim that we do, so for instance it can tell you which ball is the red one or the green one, but doesn't experience redness or greenness. ** So of course Chopra caught on to this, and has been one of the sponsors of the more recent round or two of the scientific conference, and he and Hameroff have put out one or two popular press articles together. There are a number of meditation people who come to the conference, but they tend to be the serious "Here's what an FMRI shows about blood flow in your brain while you're meditating" folks, while the cranks are more likely to have opinions about quantum. *** There are some theories of quantum mechanics that say it's still deterministic, just with underlying hidden variables that we can't observe or measure, but it's been too many decades since college physics for me to remember if those got disproved or are still around.