"Eliezer S. Yudkowsky" wrote:
> John Clark wrote:
> > I have three problems with Penrose:
> > 1) There is not one scrap of experimental evidence that it's happening
> > and there should be if it were true.
> Mm, you can argue both sides of that. Penrose & Hameroff claim that
> microtubules have several precisely tuned characteristics needed for
> quantum coherence. *I* don't think anything ineffable will show up
> until we start recording individual neurons *and* we know what to look for.
> > 2) The inside of a neuron seems to be far too hot and noisy for
> > quantum coherence to be possible, much less quantum computation.
> > You'd need new fundamental laws of physics for this to work,
> > that's another way of saying you'd need magic and I don't like
> > to invoke magic if I don't need to. I don't need to.
> Well, we're getting a bit outside my field, but I don't think that's
> true. Heat and noise is only a problem for macroscopic, crystalline
> (non-stochastic) quantum coherence. Remember that NMR-based QC (*not*
> the one we've been discussing lately) that would operate on a cup of
> coffee? And the comments about the Improbability Drive?
I have many problems with Penrose, and especially with the proposal for intraneural quantum computing (IQC). Perhaps others on this list, who know more than I, can answer some of these.
When did IQC happen in evolutional history? The basic neuron design is very old, and if we have IQC, you would expect fish and slugs to have it as well. Where are the intermediate cases?
Attempts to develop QC show that it is very difficult to keep coherence localized long enough to do anything. Yet, neurons operate over wide temperature ranges (over species), and many other conditions. Last time I stuck my head in an MRI the magnetic field aligned quite a few of my neural molecular components, but the system seemed to be the same. You will not notice a short blast of microwave energy that starts the (supposedly quantum coherent ) water in your neuro cytoskeleton dancing around. Even a lethal dose of neutron or gamma radiation that rips those molecules apart does not stop you from thinking about the fact that your cells will soon shut down.
Contrast this with the basic idea that neuron activity is electrochemical. A tiny electrical current introduced in the brain can have a major impact on thinking. Any drug that impacts neurotransmitter chemicals will do so as well. Neurotoxins can deadly in microgram quantities.
In _How Brains Think_, William Calvin has a whole chapter called, "The Janitor's Dream," in which he tries to find all the connecting levels between the QC and the thinking. He could not find them, and I can't find them either. This does not mean that they do not exist, but if someone out there can tell me how to go from pushing a broom in the basement to putting my feet up on the CEO desk with no latter climbing in-between, I promise to cut you in on some stock options.
IMHO, IQC is just another case of something that has been stuck in the debate to push the horizon of accepting strong AI farther in the cognitive future so that it can be ignored. This reminds me of the way you could beat the early chess programs by getting them to make small dumb moves to push the loss part of an even exchange off their event horizon. I think debates about qualia are the same thing, and I notice that those who spend a lot of time with qualia seem to end up at quantum. Perhaps it is a Hamming distance thing?