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

Penrose is a mystic

[Anonymous Coward]

He wants the brain to be non-computable, non-simulatable. In short, he wants it to be magic. He has no real justification for his position.

Consciousness is weird

[Hatta]

Consciousness is weird. Quantum theory is weird. Therefore quantum theory must explain consciousness.

That's essentially the argument here, and it's pretty easily seen as fallacious. There's no actual evidence that consciousness requires quantum mechanics, besides the trivial fact that our brains are chemical computers and chemistry requires quantum mechanics.

Re:Consciousness is weird

[bcrowell]

Consciousness is weird. Quantum theory is weird. Therefore quantum theory must explain consciousness.

That's essentially the argument here, and it's pretty easily seen as fallacious.

Well, the slashdot link, and the New Statesman story linked to from it, don't really do justice to Penrose's idea, so it's not surprising that you've gotten the impression that there's absolutely nothing there. Actually there's something to it, and although as a physicist I don't buy it, it's not completely stupid.

The basic idea is that there are various ways to interpret quantum mechanics. The most popular interpretations are the Copenhagen interpretation and the many-worlds interpretation (MWI).

My own take on it is that Copenhagen and MWI are just different words for talking about the theory, so the distinction isn't empirically testable. Copenhagen does a good job of depicting the psychological experience of doing experiments with quantum-mechanical systems, but Copenhagen is illogical because it gives a special role to measurement, which is actually a physical process like any other.

Penrose's idiosyncratic idea is that he takes Copenhagen seriously, so he says that measurement is somehow *different* from other physical processes. That suggests that consciousness is somehow different from other physical processes. He also claims that his idea is at least in principle empirically testable, that we should be able to see this process happen by studying neurons. He thinks there is something special going on in microtubules.

Slashdot's readers would have been a lot better off just reading the WP article on Penrose's theory.

Re:Recently?

[Angostura]

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.

This Place Is Full Of Quantum

[Nefarious Wheel]

This place is full of Quantum; it's everywhere you look

It's in the halls of Physicists, and pages of a book.

"There has to be a fallacy!" the comment summarised,

And if we care to challenge that, we aren't very wise?

Quantum Theory is not relevant

[Bugpowda]

Professional Neuroscientist here... In fact, I'm recording from a sensory neuron that is partially responsible for the conciousness of an awake behaving mouse right now while browsing slashdot.

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.

Perhaps the best, short, free, relatively recent summary of the field was written by Christof Koch and Francis Crick, A Framework for Conciousness, and is available here : http://papers.klab.caltech.edu/29/1/438.pdf

I also have a little essay on the nature of free will on my blog here, if interested. http://brainwindows.wordpress.com/philosophy/philosophy-the-science-of-free-will/

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:What fallacy?

[Zaphod The 42nd]

I suspect at some point we will come to terms with the fact that what we call "consciousness" is an emergent phenomenon of the brain, and that it is no more free than a glider in Conway's Game of Life.

Bingo.