Thursday, December 08, 2005

Stapp and Quantum Agents

For several decades now, physicist Henry Stapp has been publishing books and papers which develop an explanation of human consciousness grounded in quantum mechanics (an online list of Stapp’s papers from recent years is here). I just read this new article, published in the Journal of Consciousness Studies. This particular article includes a review of his general approach in layman-accessible terms, and then highlights his proposed linkage of the efficacy of conscious will to the quantum zeno effect. This is interesting stuff, and I would highly recommend that students of consciousness read Stapp. For now, I have a brief comment (which is off the main topic of the paper) on a set of long standing questions I have about Stapp’s work: if quantum effects are needed to explain the workings of the human brain, aren’t they also needed to explain other macroscopic phenomena? Is it only in the human brain where a classical approximation fails to provide a full explanation? In terms of causation, are human beings the only quantum agents?

In other words, I feel like we’re missing some steps in our description of reality. Humans, after all, evolved from lower forms of life. Life itself was bootstrapped out of the inorganic world. While human consciousness is unique in so many ways, it seems most plausible that humans leverage capabilities inherent in other natural systems, rather than utilize utterly unique mechanisms.

Stapp seems surely right when he says that certain brain processes are grounded in the quantum realm (he cites the size of ionic channels between synapses as being on a scale where quantum effects must exist). But couldn’t this be true of cellular processes outside the brain, too? How about in single-celled animals? If quantum interactions (=measurements) are the raw material of the macroscopic world (as I speculated in my recent post), shouldn’t this be in evidence in realms other than the human brain?

Here’s a comment from Stapp on this (made somewhat as an aside):

"But if one considers the Von Neumann theory to be an ontological description of what is really going on, then one must of course relax the anthropocentric bias, and allow agents of many ilks. Yet the theory entails that it would be virtually impossible to determine, empirically, whether a large system that is strongly interacting with its environment is acting as an agent or not. This means that the theory, regarded as an ontological theory, has huge uncertainties.
However, our interest here is the nature of human agents. Hence the near impossibility determining the possible existence of other kinds of agents, will mean that our lack of information about the existence of those other possible kinds of agents will have little or no impact on our understanding of ourselves."

This seems too quick of a dismissal of the ubiquity of quantum agents. For what it’s worth, here’s my alternative view of how things could work. Macroscopic systems in nature can be described in terms of systems which coordinate quantum micro-agents. The raw material of first person experience and intentionality comes from small quantum interactions, which are then leveraged through special functional networks in human brains to give rise to the familiar large scale features of consciousness. This account would be consistent with the fact that consciousness is tied intimately to the specific structures of the brain while also addressing why the deepest mysteries of consciousness (why there is first person experience and intentionality at all) are impervious to description in classical terms.

The research agenda to get at these issues would include trying to figure out whether single-celled animals might utilize quantum effects and whether quantum physics plays any role in an account of the origin of life.

6 comments:

Richard Jordan said...

Great link there... I found this a pretty compelling argument for QM as a solution to the binding problem

Steve said...

Hi Richard. Yes, but we still can only speculate about the precise mechanisms thru which QM may be utilized. The good news is that this is amenable to scientific research. My hope is that more people will target this area, which I fear falls through the cracks between physics, biology and neuroscience.

Mike Wiest said...

I agree that Stapp's argument for QM for binding is compelling (in "Why Classical Mechanics Can't Accomodate Consciousness but QM Can"). But Steve, wasn't it you who considered it highly unlikely that QM was relevant to the brain/mind on the Conscious Entities blog? Have you changed your mind?

And I agree that it is by looking for the mechanisms that we will be able to test these ideas. I'd like to contribute to that effort myself if I can. (I'm trained in physics and now doing research in neuroscience.) My problem with Stapp's suggestion and also the spin-based consciousness idea is that I don't know what to look for in the brain. It's hard to see how proton spins in the cell membranes would become systematically related to the classical neural activities, so that they might have something relevant to say to each other. So, for puposes of testing the quantum mind hypothesis, at this point I favor the idea that global states of the cytoskeleton (eg photons in microtubules)condition and coordinate the probabilities of neurtransmitter release at synapses. The liquid crystal nature of actin and other biomolecules is like the gates used in optical computers, so this doesn't seem too crazy...and it might be testable...

For a fascinating look at intelligence and subtle physical effects (electromagnetic) in single-celled organisms check out Albrecht-Buehler's work :
http://www.basic.northwestern.edu/g-buehler/summary.htm

Steve said...

Hi Mike.

I don’t think I’ve changed my mind. My position (FWIW) is that the brain seems unlikely to utilize QM effects in the sense of preserving coherent superpositions (or entanglement) at a macroscopic scale (e.g. at the level of neuronal assemblies). On the other hand I do think QM will be relevant to explaining living organisms (and therefore, of course, the human brain) since they will be shown to utilize QM effects at the micro-level. The brain could possibly leverage and coordinate these micro-effects without needing to have global quantum superpositions.

Of course, this is just complete speculation on my part. Your idea sounds like a great one to investigate. Thanks also for the reference – I’ll check it out.

Mike Wiest said...

I see. I guess my problem with the suggestions that don't commit to macroscopic coherence in the brain, is that you would seem to lose all the binding that was the motivation for QM in the first place (from my perspective anyway). For example, if red is represented at the back of your head and ball is represented by your ear, I want an entangled macroscopic state to give you a substrate for a unified percept of "red ball."

This isn't anything like a proof, of course, so I'm all for continuing to consider all the possibilities...

Steve said...

I agree with that last sentiment. And thanks for your comments.
- Steve