evolutionary and computational theories of mind

mat mats_trash at hotmail.com
Mon Jan 21 05:27:43 EST 2002


"C.J.L. Wolf" <C.J.L.Wolf at ncl.ac.uk> wrote in message news:<Pine.SOL.4.21.0201191654530.7114-100000 at aidan.ncl.ac.uk>...
> > > 
> > Why should there be computational ciruits in the brain? Computers have
> > only been around for 50 years, might nature not have given us
> > something slightly more honed?  The computational theory makes the
> > very big suppoition that the outputs we get from our minds are the
> > result of logical operations upon the sensory stuff that went in. 
> > However, the output only seems *right* becuase everyone's is generally
> > the same or similar.  If everyone behaved totally differently then
> > that would be reagrded as the *right* output too.
> > 
> I think this is rather a misconception of what computational neuroscience
> actually is. Few if any computational theorists would argue that the brain
> operates in the binary, intensely logical way that a computer does; rather
> computational neuroscience recognises that brains essentially do
> operations on information - and tries to make out what those operations
> must be.

To an extent maybe, but much of the computational theory of mind is
based on syntax in language etc and logical operations upon this
syntax.  i.e. that the brain computes the 'meaning' in words through
operations upon its syntax.  The argument is then whether the brain is
a 'intensely logical' computer or its computational abilities arise at
a higher level, similar to the difference in the way a computer might
process the binary digit '1' and process the word 'one'.  Though they
both have the same meaning to us, the word one would have to be
represented at a higher level in a computer.  Further, logic itself
has 'come from' the brain.  At some level the brain must be able o
perform logical operations but is this at hardware or software level?

> 
> For example: 
> 
> If you are in a darkened room, looking at a blue object, does
> it appear blue because it reflects more short wavelength light than long /
> medium wavelength light? Or could it be that the light shining on it is
> blue?
> 
> Computational neuroscience first defines what info is available to your
> brain as it tries to solve the ambiguity. For example, it may be that
> there is a little mirror like reflection on the object (specularity).
> There are other cues too - but I'm just going to talk about this one.
> 
> You then describe the algorithm - look at the reflection; check that it is
> a specularity (it should be bright, and have fuzzy edges, and if you focus
> on it, then the rest of the object will be out of focus). If it is blue,
> then the lighting is blue, and the object should probably appear greyer
> than first assumed. But if the reflection is white, then the object should
> be blue.
> 
> The final stage is to implement the algorithm. You could easily do it on a
> computer; that certainly isn't to imply your brain would implement it in
> the same way if indeed it implements it at all. But you could look at how
> well the computer algorithm performs and compare that to a human
> observer's performance - this is more the realms of psychology. At the
> very least, if we find that the algorithm doesn't work in its computer
> implementation, this tells us that we got the algorithm wrong, or at least
> incomplete.
> 
> For a good introduction, try David Marr's book, 'Vision'. I believe that
> he also discussed evolutionary reasons why modularity is desirable. It
> centered on being able to make changes module by module - if one didn't
> have the degree of finesse that this bestows, it would be very difficult
> to make changes to one system (e.g. vision) without making changes to all
> systems (e.g. the auditory system also) that could very well be
> counterproductive.
> 
> As an example, I heard that there is a sort of sheep that was bred in
> yorkshire to have short legs to save work in building high stone walls to
> keep them in. If different genes governed the development of front legs
> and back legs (or even worse - left and right legs - though this is the
> case for haggis, of course) then some rather awkward animals could have
> resulted so it's just as well that leg development is pleiotrophic. On the
> other hand, if one also wanted this sheep to have long ears so it could
> hear predators from far away, and if ear length was governed by the genes
> for leg length, then it would be very difficult to breed sheep with short
> legs and long ears, even though in the environment of a Yorkshire dale,
> this was desirable.
> 
> KW

These examples are not quite what I what I was talking about.  The way
the brain interprets sensory information is one thing, but the
conscious acts of thinking etc are another




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