rbg@cbosgd.UUCP (Richard Goldschmidt) (06/14/84)
> I believe there are aprroximately 10 to the 9th neurons in a human > brain, if that's of any help. Add in the glial cells (there is some > debate about their function) and it comes to 10 to the 10th. > Bob Binstock Those numbers are both wrong, but so was the number in my original posting. Let me correct the numbers, and add the discussion to some other groups which may or may not be interested. Recent estimates of the number of neurons in the human brain have been increasing, for a current estimated total of between 30x10^9 and 50x10^9. Glial cells outnumber neurons by at least 10 to one, and occupy about half the volume of the brain, but the ratio varies widely between brain regions, and between species within a brain region. To get an estimate of the computational equivalent of the brain: Assume 5x10^10 neurons with 2x10^4 synapses each = 10^15 synapses/brain. Each synapse, on average, adds in a quantity about 20 times/sec (it can go much faster, but not many do at the same time). So that's 2x10^16 very simple approximate adds per second. Even when everything is just right, a Cray can't do better than about 10^9 simple integer adds per sec. So, IF THE SYNAPSES ARE BEING USED WITH TOTAL EFFICIENCY FOR PERFORMING THE TASK, a brain is worth about 10^7 Crays. [Credit for this calculation to Terry Sejnowski (Biophysics, Johns Hopkins) and Geoff Hinton (Computer Science, Carnegie-Mellon)]. It is not surprising that most tasks use only a small fraction of this capacity. However, I think the computation of the amount of information used to store sensory perceptions by hound!rfg may be misleading: >>if I assume a visual field as 10**3 bits high by 10**4 bits wide >>by 10 bits for color and shading of each element, we have 10**8 bits >>per visual field. Suppose a life time of 72 years and 16 hours a day of >>observing (neglecting "visual dreams" which may also be remembered), >>with a new observation every 10 seconds. I multiply it all out to >>about 1.5 x 10**16 bits. (187,500 billion bytes?) >>Adding audio, tactile, olfactory, taste to that ought to easily run the >>total over 200 gigabytes. That's just for remembering observations >>(eidetically, which is a faculty some do have). Most people do not remember every detail of every scene they ever see. How much of your early childhood (0-4) do you even remember at all? Emotional content of a situation can have a large impact on what and how much you recall. Dangerous or joyful experiences stand out in memory more than most neutral events. The role of language is also an important issue in considering the storage and information processing capacity of the brain. Using a word to stand for the many features which make up an object or a concept is an incredible data compression. This may be why the gradual increase in computational ability across primate evolution is not a very satisfying explanation for the quantum leap in human intellectual ability. Many of the explanations of the origin of consciousness rely on the advantages of language for improving analytic ability. The one I like best is Julian Jaynes idea (The Origin of Consciousness in the Breakdown of the Bicameral Mind): that consciousness is not just a simple consequence of language, but that the exponential growth in knowledge fostered by language generates self-consciousness only after certain kinds of concepts are introduced into language. This allows him to trace the evolution of consciousness by literary analysis! Rich Goldschmidt -- a former brain hacker (now reformed?) cbosgd!rbg
lwt1@aplvax.UUCP (06/18/84)
The other thing to note is that while each 'memory cell' in a computer has ~2 connections, each 'memory cell' in the brain has ~100. Since processing power is relative to (cells * connections), a measure of relative capacities is not sufficient for comparison between the brain and the CRAY. -Lloyd W. Taylor ... seismo!umcp-cs!aplvax!lwt1 ---I will have had been there before, soon---
crane@fortune.UUCP (John Crane) (06/18/84)
Up to this point the ongoing discussion has neglected to take two things into account: (1) Subconscious memory - a person can be enabled (through hypnosis or by asking him the right way) to remember infinite details of any experience of this or prior life times. Does the mind selectively block out trivia in order focus on what's important currently? (2) Intuition - by this I mean huge leaps into discovery that have nothing to do with the application of logical association or sensual observation. This kind of stuff happens to all of us and cannot easily be explained by the physical/mechanical model of the human mind. I agree that if you could build a computer big enough and fast enough and taught it all the "right stuff", you could duplicate the human brain, but not the human mind. I don't intend to start a metaphysical discussion, but the above needs to be pointed out once in a while. John Crane
stewart@ihldt.UUCP (R. J. Stewart) (06/19/84)
> (1) Subconscious memory - a person can be enabled (through > hypnosis or by asking him the right way) to remember > infinite details of any experience of this or prior life > times. I don't know where the "prior life" part came from, but this claim is usually an incorrect extrapolation of studies that indicate no such thing. What has been established is that people can be induced to remember things that they considered forgotten. This isn't by a long shot the same thing as saying that we remember everything that's ever happened to us. If you have evidence to support this claim, by all means present it. If not, please spare us. Bob Stewart ihldt!stewart
bill@utastro.UUCP (William H. Jefferys) (06/19/84)
> (1) Subconscious memory - a person can be enabled (through > hypnosis or by asking him the right way) to remember > infinite details of any experience of this or prior life > times. Does the mind selectively block out trivia in order > focus on what's important currently? One of the reasons that evidence obtained under hypnosis is inadmissable in many courts is that hypnotically induced memories are notoriously unreliable, and can often be completely false, even though they can seem extremely vivid. In some states, the mere fact that a witness has been under hypnosis is enough to disqualify the individual's testimony in the case. I have personal, tragic experience with this phenomenon in my own family. I don't intend to burden the net with this, but if anyone doubts what I say, I will be glad to discuss it by E-mail. -- Bill Jefferys 8-% Astronomy Dept, University of Texas, Austin TX 78712 (USnail) {allegra,ihnp4}!{ut-sally,noao}!utastro!bill (uucp) utastro!bill@ut-ngp (ARPANET)
riddle@ut-sally.UUCP (Prentiss Riddle) (06/20/84)
Now that Chuqui's obligingly created net.sci, why don't we move this
discussion there? Is there any reason for it to go on in five
newsgroups simultaneously? If interest continues, perhaps this topic
will form the basis for net.sci.psych.
Followups to net.sci, please.
--- Prentiss Riddle ("Aprendiz de todo, maestro de nada.")
--- {ihnp4,harvard,seismo,gatech,ctvax}!ut-sally!riddlehenry@utzoo.UUCP (Henry Spencer) (06/21/84)
John Crane cites, as evidence for the human mind being impossible to
duplicate by computer, two phenomena.
(1) Subconscious memory - a person can be enabled (through
hypnosis or by asking him the right way) to remember
infinite details of any experience of this or prior life
times. Does the mind selectively block out trivia in order
focus on what's important currently?
As far as I know, there's no evidence of this that will stand up to
critical examination. Even disregarding the "prior life times" part,
for which the reliable evidence is, roughly speaking, nonexistent,
the accuracy of recall under hypnosis is very doubtful. True, the
subject can describe things in great detail, but it's not at all proven
that this detail represents *memory*, as opposed to imagination. In
fact, although it's quite likely that hypnosis can help bring out things
that have been mostly forgotten, there is serious doubt that the memories
can be disentangled from the imagination well enough for, say, testimony
in court to be reliable when hypnosis is used.
(2) Intuition - by this I mean huge leaps into discovery
that have nothing to do with the application of logical
association or sensual observation. This kind of stuff
happens to all of us and cannot easily be explained by
the physical/mechanical model of the human mind.
The trouble here is that "...have nothing to do with the application
of logical association or sensual observation..." is an assumption,
not a verified fact. There is (weak) evidence suggesting that intuition
may be nothing more remarkable than reasoning and observation on a
subconscious level. The human mind actually seems to be much more of
a pattern-matching engine than a reasoning engine, and it's not really
surprising if pattern-matching proceeds in a haphazard way that can
sometimes produce unexpected leaps.
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henrybill@utastro.UUCP (William H. Jefferys) (06/23/84)
Apropos this discussion, there has been research into hypnotically
aided recall that casts serious doubt on its reliability.
Two recent articles in *Science* magazine directly address this issue:
"The Use of Hypnosis to Enhance Recall", Oct 14, 1983, pp. 184-185 and
"Hypnotically Created Memory Among Highly Hypnotized Subjects", Nov 4,
1983, pp. 523-524.
--
Bill Jefferys 8-%
Astronomy Dept, University of Texas, Austin TX 78712 (USnail)
{allegra,ihnp4}!{ut-sally,noao}!utastro!bill (uucp)
utastro!bill@ut-ngp (ARPANET)