Connectionists: Physics and Psychology (and the C-word)

[Randall O'Reilly]

Carson -- yeah I need to fix that part about the massive particles -- that has been pointed out to me and was just sloppy on my part.  I don't think it changes the fundamental points though -- I just focus on the photon case because it is where all the experimental action is, and the issues seem particularly clear there.

I don't know why it is so hard to communicate in the context of physics this difference between a mechanistic model and a calculational tool, which is at the core of my issue with QM.  I completely agree that QM in Hilbert space is a clean, clear, nice calculational tool.  But I just don't see how nature could do anything like it.  Going up to the neuroscience level, it seems perfectly clear to everyone to say that a Bayesian or other abstract mathematical model can capture the relevant behavior, but it doesn't capture the way that the brain actually does it (through neurons and ion channels and whatnot).  There may not be (and unless you're incredibly lucky, almost certainly isn't) a direct isomorphism between the variables in the abstract model and those in the brain.  But you can capture the behavior very accurately.  This is just two different levels of description of the same phenomenon.

In physics, things are simple enough that you can have multiple different ways of describing the exact same thing that are *completely isomorphic* -- they are truly indistinguishable.  The example in the paper is the Coloumb vs. Lorenz gauge formulations of EM, but there are many others.  I claim that the Lorenz gauge is something that nature could compute (it is local, simple wave equation, easily implemented in a cellular automaton, etc).  My key point then is that there isn't an equivalent representation of QM that has these same properties.  It is all done in fourier space with perturbative expansions and whatnot, which are not something that nature could locally, tractably compute.  Maybe I'm just crazy but this just seems self-evident to me, but I have the hardest time communicating it!  Cheers,

- Randy

On Jan 28, 2014, at 1:49 PM, Carson Chow <ccchow at pitt.edu> wrote:

> Randy,  I just skimmed your screed against physics and while I agree that most physicists don't pay attention to the foundations of quantum mechanics and I sympathize with your angst, I still must disagree with some of your assertions.  
> 
> It is not true that only entangled photons can demonstrate nonlocality. Once two massive particles are outside of their respective light cones, they are no longer causally related by the speed-of-light.  If you have two measuring devices setup very far apart and you can keep the two particles coherent then they will violate Bell's inequalities.  The fact that it took them a long time to get to the space-like separation is irrelevant.  All that matters is once they are far enough apart they are causally separated but Bell's inequalities will still be violated.  I also believe that Alain Aspect's experiments show photon entanglement.
> 
> QED is manifestly Lorentz covariant so photons do travel at the speed of light in the theory.    Also, the Langrangian for all quantum field theories have the same form as Maxwell's equations that you like so much.  I also don't really follow what you are so distrubed about with regards to the locality of photons.  The normal modes of photons are indeed pure Fourier modes but the photons that you know and love come in wave packets, which imparts locality to them.  I'm not sure why this bothers you. 
> 
> I think you also impart some advantage to semi-classical calculations over QM that don't seem warranted.  All calculations in QFT are perturbational and there are basically two small parameters you can use - the coupling constant, e.g. alpha, or Planck's constant hbar.  A semi-classical calculation (also called a loop expansion) just uses small hbar.  The agreement to experiments like the Lamb shift or electron-photon scattering, etc do improve as you go to higher order in the loop expansion.
> 
> As mathematics, Quantum mechanics is beautifully self-consistent and rather simple.  All you need is unitary transformation of a state function in Hilbert space together with the Born rule.  You may find that distasteful as a representation of reality but I find that much more satisfying than our confusing nonlinear classical world.  I think the biggest puzzle in quantum mechanics is the origin of the Born rule.  Why is the L2 norm squared of the amplitude probability?
> 
> Anyway, I had no idea you were thinking about these things.
> 
> cheers,
> Carson
> 
> 
> On 1/28/14 2:12 PM, Randall O'Reilly wrote:
>> I’m glad to hear this counterpoint to all this physics envy — I took a deep dive into the current state of theory in quantum physics a while back, and was pretty shocked at what a mess it is!  Sure, it works (“shut up and calculate” is a mantra) but from a conceptual level, there are some pretty serious unresolved issues, which don’t seem to be very widely appreciated in the lay press, with all those rah-rah unified theory books.
>> 
>> The core issue is relevant for the discussion here: physics does NOT actually have anything approaching a “mechanistic” model — it is all a descriptive calculational tool.  In other words, you can compute the right answers, but this is clearly not how “nature computes physics”.  Indeed, the notion of finding such a mechanistic model is considered naive and has long since been abandoned.
>> 
>> Translating this to our field: the Bayesians have won, and nobody cares about how neurons actually work!  As long as you can compute the “behavioral” outcome of experiments (to high precision for sure), the underlying hardware is irrelevant.  And those calculations seem a lot like the epicycles: you need to compute more and more terms in infinite sums to reach ever-closer approximations to the truth, with the seemingly arbitrary renormalization procedure added in to make sure everything converges.  Do we think that nature is using the same technique?
>> 
>> Anyway, I wrote up a critique and submitted it to a physics journal: 
>> http://arxiv.org/abs/1109.0880
>> 
>> Not surprisingly, the paper was not accepted, but the review did not undermine any of the major claims of the paper, and just reiterated the “standard” lines about the whole entanglement issue, denying the validity of the various papers cited raising serious questions about this.
>> 
>> I did make some friends in the “alternative” physics community from that paper, and I am currently (very slowly) working on a “neural network” inspired model of quantum physics, described here:  
>> http://grey.colorado.edu/WELD/index.php/WELDBook/Main
>>  — in this model, everything emerges from interacting wave equations, just like we think everything in the brain emerges from interacting neurons..
>> 
>> - Randy
>> 
>> On Jan 28, 2014, at 8:03 AM, Kaare Mikkelsen 
>> <mikkelsen.kaare at gmail.com>
>>  wrote:
>> 
>> 
>>> Speaking as another physicist trying to bridge the gap between physics and neuroscience I must also say that how the most abstract ideas from quantum mechanics could meaningfully (read: scientifically) be applied to macroscopic neuroscience, given our present level of understanding of either field, is beyond me. To me, it is at the point where the connection is impossible to prove or disprove, but seems very unlikely. I do not see how valid scientific results can come in that direction, seeing as there is no theory, no reasonable path towards a theory, and absolutely no way of measuring anything. 
>>> 
>>> --------------------------------------------------------------------
>>> Kaare Mikkelsen, M. Sc.
>>> Institut for Fysik og Astronomi
>>> Ny Munkegade 120
>>> 8000
>>> Aarhus C
>>> Lok.: 1520-629
>>> Tlf.: 87 15 56 37
>>> --------------------------------------------------------------------
>>> 
>>> 
>>> On 28 January 2014 15:32, Richard Loosemore 
>>> <rloosemore at susaro.com>
>>>  wrote:
>>> On 1/27/14, 11:30 PM, Brian J Mingus wrote:
>>> Consciousness is also such a bag of worms that we can't rule out that qualia owes its totally non-obvious and a priori unpredicted existence to concepts derived from quantum mechanics, such as nested observers, or entanglement.
>>> 
>>> As far as I know, my litmus test for a model is the only way to tell whether low-level quantum effects are required: if the model, which has not been exposed to a corpus containing consciousness philosophy, then goes on to independently recreate consciousness philosophy, despite the fact that it is composed of (for example) point neurons, then we can be sure that low-level quantum mechanical details are not important.
>>> 
>>> Note, however, that such a model might still rely on nested observers or entanglement. I'll let a quantum physicist chime in on that - although I will note that according to news articles I've read that we keep managing to entangle larger and larger objects - up to the size of molecules at this time, IIRC.
>>> 
>>> 
>>> Brian Mingus
>>> 
>>> http://grey.colorado.edu/mingus
>>> 
>>> 
>>> Speaking as someone is both a physicist and a cognitive scientist, AND someone who has written papers resolving that whole C-word issue, I can tell you that the quantum story isn't nearly enough clear in the minds of physicists, yet, so how it can be applied to the C question is beyond me.  Frankly, it does NOT apply:  saying anything about observers and entanglement does not at any point touch the kind of statements that involve talk about qualia etc.   So let's let that sleeping dog lie.... (?).
>>> 
>>> As for using the methods/standards of physics over here in cog sci ..... I think it best to listen to George Bernard Shaw on this one:  "Never do unto others as you would they do unto you:  their tastes may not be the same."
>>> 
>>> Our tastes (requirements/constraints/issues) are quite different, so what happens elsewhere cannot be directly, slavishly imported.
>>> 
>>> 
>>> Richard Loosemore
>>> 
>>> Wells College
>>> Aurora NY
>>> USA
>>> 
>>> 
>>> 
>> 
>