>Mike Tintner #####> Yes, I understood that (though sure, I'm capable of misunderstanding anything here!)
ED PORTER #####> Great, I am glad you understood this. Part of what you said indicated you did. BTW, we are all capable of misunderstanding things. >Mike Tintner #####> Hawkins' basic point that the brain "isn't a computer at all" - which I think can be read less controversially as "is a machine that works on very fundamentally different principles to those of currently programmed computers - especially when perceiving objects" - holds. You're not dealing with that basic point, and I find it incredibly difficult to get anyone here squarely to face it. People retreat into numbers and millions. ED PORTER #####> I think most of us understand that and are not disputing it. A Novamente-like approach to AGI is actually quite similar to Hawkins' in many way. For example, it uses hierarchical representation. So few of us are talking about Old Fashioned AI as the major architecture for our systems (although OFAI has its uses in certain areas). >Mike Tintner #####> P.S. You also don't answer my question re: how many neurons in total *can* be activated within a half second, or given period, to work on a given problem - given their relative slowness of communication? Is it indeed possible for "hundreds of millions" of messages about that one subject to be passed among millions of neurons in that short space (dunno-just asking)? Or did you pluck that figure out of the air? ED PORTER #####> I was not aware I had been asked this question. If you are asking where I got the it-probably-takes-hundreds-of-millions-of-steps-to-recognize-a-face, I was sort of picking it out of the air, but I don't think it is unreasonable pick. I was including each synaptic transmission as a step. Assume the average neuron has roughly 1K active synapses (some people say several thousand some say only about 100), and lets say an active cell fires at least ten times during the 100 step process, and since you assume 100 levels of activation, that would only be assuming an average of 100 neurons activated on average at each of your 100 levels, which is not a terribly broad search. If a face were focused on, so that it took up just the size of your thumbnail with you thumb sticking up with your arm extended fully in front of your that would activate a portion of your foviated retna having a resolution of roughly 10k pixels (if I recollect correctly from a conversation with Tomaso Poggio). Presumably this would include 3 color inputs, a B&W input, and with mangocellur and pravocellur inputs from each eye, so you may well be talking about 100k neurons actived at just the V1 level. If each has 1K neurons firing 10 times, that's 10k x 100K or 100M synaptic firings right there, in just one of your 100 steps. Now some of that activation might be filtered out by the thalamus, but then you would have to include all its activations used for such filtering, which according to Stephen Grossberg involves multi-level activations in the cortico-thalamic feedback loop, which probably would require roughly at least 100M synaptic activations. And when you recognize a face you normally are seeing it substantially larger than your thumb nail at its furthest extension from your face. If you saw it as large as the length of your entire thumb, rather than just your thumbnail, it would project on to about 10 times as many neurons in your thalamus and V1. So, yes, I was guessing, but I think hundreds of millions of steps. AKA synaptic activations, was a pretty safe guess. Ed Porter -----Original Message----- From: Mike Tintner [mailto:[EMAIL PROTECTED] Sent: Friday, December 07, 2007 5:08 PM To: [email protected] Subject: Re: [agi] Do we need massive computational capabilities? ED PORTER #####> "When you say "It only takes a few steps to retrieve something from memory." I hope you realize that depending how you count steps, it actually probably takes hundreds of millions of steps or more. It is just that millions of them are performed in parallel, such that the longest sequence of any one causal path among such steps is no longer than 100 steps. That is a very, repeat very, different thing that suggesting that only 100 separate actions were taken. Ed, Yes, I understood that (though sure, I'm capable of misunderstanding anything here!) But let's try and make it simple and as concrete as possible - another way of putting Hawkins' point, as I understand, is that at any given level, if the brain is recognising a given feature of the face, it can only compare it with very few comparable features in that half second with its 100 operations - whereas a computer will compare that same feature with vast numbers of others. And actually ditto, for that useful Hofstadter example you quoted, of proceeding from aabc: aabd to jjkl: ??? (although this is a somewhat more complex operation which may take a couple of seconds for the brain), again a typical intelligent brain will almost certainly consider v. few options, compared with the vast numbers of options considered by that computer. Ditto, for godsake, a human chessplayer like Kasparov's brain considers an infinitesimal percentage of the moves considered by Big Blue in any given period - and yet can still win (occasionally) because of course it's working on radically different principles. Hawkins' basic point that the brain "isn't a computer at all" - which I think can be read less controversially as "is a machine that works on very fundamentally different principles to those of currently programmed computers - especially when perceiving objects" - holds. You're not dealing with that basic point, and I find it incredibly difficult to get anyone here squarely to face it. People retreat into numbers and millions. Clearly the brain works VASTLY differently and more efficiently than current computers - are you seriously disputing that? P.S. You also don't answer my question re: how many neurons in total *can* be activated within a half second, or given period, to work on a given problem - given their relative slowness of communication? Is it indeed possible for "hundreds of millions" of messages about that one subject to be passed among millions of neurons in that short space (dunno-just asking)? Or did you pluck that figure out of the air? P.P. S. A recent book by Read Montague on neuroeconomics makes much the same point from a v. different angle - highlighting that computers have a vastly wasteful search heritage which he argues has its roots in Turing and Bletchley Park's attempts to decode Engima. _____ This list is sponsored by AGIRI: http://www.agiri.org/email To unsubscribe or change your options, please go to: http://v2.listbox.com/member/? <http://v2.listbox.com/member/?&;> & ----- This list is sponsored by AGIRI: http://www.agiri.org/email To unsubscribe or change your options, please go to: http://v2.listbox.com/member/?member_id=8660244&id_secret=73861513-4a2066
