Picture: Binocular rivalry. The idea that quantum mechanics is part of the explanation of consciousness, in one way or another, is supported by more than one school of thought, some of which have been covered here in the past. Recently MLU was quick to pick up on a new development in the shape of a paper by Efstratios Manousakis which claims that testable predictions based on the application of quantum theory have been borne out by experiment.

The claims made are relatively modest compared to those of Penrose and Hameroff, say. Manousakis is not attempting to explain the fundamental nature of conscious thought, and the quantum theory he invokes isn’t new. At its baldest, his paper merely suggests that dominance duration of states in binocular rivalry can be accurately modelled by assuming we’re dealing with a small quantum mechanical system embedded in a classical brain – although if that much were true, it would certainly raise further issues.

But let’s take it one step at a time. What is binocular rivalry, to begin with? When radically different images are presented to the left and right eye, instead of a blurry mixture of both images, we generally see one fairly clearly (occasionally a composite made of bits of both images); but curiously enough, the perceived image tends to switch from one to the other at apparently random intervals. Although this switching process can be influenced consciously, it happens spontaneously and therefore seems to be a kind of indecisiveness in some unconscious mechanism in our visual system.

Manousakis proposes a state of potential consciousness, with the two possible perceptions hanging in limbo. When the relevant wave function is collapsed through the intervention of another, purely classical brain mechanism, one or other of the appropriate neural correlates of consciousness is actualised and the view through one eye or the other enters actual consciousness. This model clearly requires perception to operate on two levels; one, a system that generates the potential consciousness, and two, another which actualises states of consciousness by checking up every now and then.

Thus far we have no particular reason to believe that the application of quantum concepts is anything more than a rather recondite speculation; but Manousakis has shown that the persistence of one state in the binocular rivalry, and the frequency of switching, can be predicted on the basis of his model: moreover, it explains and accurately predicts another observed phenomenon, namely that if the stimuli in a binocular rivalry experiment are removed and returned at intervals, the frequency of switching is significantly reduced. If I’ve understood it correctly (and I’m not quite sure I have), one of the two images tends to stay around because when you collapse the wave function a second time, there is a high probability of it collapsing the same way. If you remove the images for a while, no new collapses can occur until the images return. It’s as though you were throwing a dice and moving to the other state when you threw a six; if you keep throwing, the changes will happen often, but if you take the dice away for a few minutes between each throw, the changes will become less frequent.

Manousakis has also demonstrated that his theory is consistent with the changes observed in subjects who had taken LSD (a slightly puzzling choice of experiment – I’m slightly surprised it’s even legal – but it seems it reflects established earlier findings in the field).

So – a breakthrough? Possibly, but I see some issues which need clearing up. First, to nail the case down, we need better reasons to think that no mere classical explanation could account for the observations. There might yet be easier ways to account for changes in dominance duration. We also need some explanation of why quantum mechanics only seem to apply in unusual cases of ambiguity like binocular rivalry. A traditional theorist who attributes binocular rivalry to problems with the brain’s interpretative systems has no trouble explaining why the odder effects only occur when we impose special interpretive challenges by setting up unusual conditions: but if a quantum mechanical system is doing the job Manousakis proposes, I would have thought occasional quantum jumps would have been noticeable in ordinary perception, too.

It would help, in addition, to have a clearer idea of how and why quantum mechanics is supposed to apply here. It could presumably be that potential consciousness is generated at a microscopic level where quantum effects would naturally be observable: an account of how that works would be helpful – are we back with Penrosian microtubules? However, Manousakis seems to leave open the possibility that we’re merely dealing with an analogy here, and that the maths he employs just happens to work for both good old-fashioned quantum effects and for a subtle mental mechanism whose basic nature is classical. That would be interesting in a different way.

It will be interesting, in any case, to see whether anyone else picks up on these results.


  1. 1. Alejandro says:

    Quantum physicist Chad Orzel has a post on Manousakis’ paper. He was not impressed.

  2. 2. steve esser says:

    I think your take on it is probably the right one. Suggestive, but no reason to think a classical mechanism couldn’t do it also.
    I predict we’ll continue to find evidence of biological systems utilizing quantum effects at a scale previously thought too macroscopic. And I think this will someday include the brain. But I infer from the recent research showing quantum effects in plant photosynthesis that direct detection of this (as opposed to fitting data to a model) poses an extreme technical challenge.

  3. 3. Peter says:

    Thanks, both of you. It looks as if the general reaction is not one of great excitement so far.

  4. 4. nick mann says:

    Just stumbled across this discussion. A group, including physicists (among them Dirk Aerts & Sven Aerts) and at least one cognitive scientist (Liane Gabora) at the Centre Leo Apostel of the Free University of Brussels have been saying for many years that there are quantum isomorphisms evident in the macroworld. Their proof? Certain macrosystems can be interpreted as violating the Bell and CHSH inequalities more robustly than any particle system experiments ever have.

    They’re at pains to say that these violations don’t need to imply actual quantum physical effects. Just an isomorphic patterning. But even so …

  5. 5. Gilbert Wesley Purdy says:

    I’ve only glanced at the paper to this point. As a result, my comments are about the conversation about it, here and at Uncertain Principles, on the Net. I would expect to find two schools of thought about “quantum consciousness”: 1) The school of the rigorously classical experimental model; and, 2) The school composed of people who want to bastion the idea of the freedom of the human will by escaping classical determinism. School #1 would say that the theory is not supported by the data. School #2 would say that the results are interesting and be pleased to believe that a basis may have been found for free will.

    While school #1 may be mistaken, given that a claim that a non-classical quantum effect may be expressed at a super-atomic level is involved, it is still the only school for developing data to support quantum effects. Should Manousakis’s conjecture be true, more supporting data will presumably bring the members of the school around. While school #2 may be correct, it is a matter of “desire” rather than Manousakis having presented any compelling evidence. Upon such a basis the paper describes an interesting line of thought regardless of whether the data it presents is compelling or not.

    In which (if either) of the two schools Manousakis himself falls is not clear. “[W]e have assumed that we are dealing with a limited quantum system imbedded in a classical brain” he informs the reader. Why this assumption rather than another who can say?

    Throughout all of this, the one assumption that never seems to be questioned is that anyone knows what exactly what we mean, in such debates as this, when we use the phrase “free will”. Why would super-atomically expressed mechanisms of quantum-style indeterminism amount to “free will”? Should such expressions actually exist as integral aspects of the function of the brain wouldn’t they have to be expressed at least as predictable statistical events in the classical sense which would leave determinism apparently intact? (Isn’t this why the classical argument being used against the paper — that the results can be explained in classical-statistical terms — is no more compelling than theory that it meant to rebut?) Or as events too inconsequential or rare to establish any brain characteristics including presummed free will?

  6. 6. Knud Thomsen says:

    The Ouroboros Model a practical and un-mystical account that can explain the reported observations without resorting to genuine quantum effects ( http://www.neuroquantology.com/journal/index.php/nq/article/view/188/170 ). A link to a more extensive paper on the Ouroboros Model together with insightful comments can be found on this site in an entry dated June 1, 2008.

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