From: Godfrey Steve (sg698@ecs.soton.ac.uk)
Date: Tue May 01 2001 - 13:06:43 BST
Searle: Is the Brain a Digital Computer? (Yusuf Larry)
>> SEARLE:
>> So our question is not, "Is the mind a program?" The answer to that is, "No"
>> Nor is it, "Can the brain be simulated?" The answer to that is, "Yes".
>Yusuf:
>The answer might be yes but how much does it help us at the end of the day.
>Just like a plane simulation can't fly, a simulation of the brain is just
>that a simulation, i.e an imitation of the behaviour of some exisiting or
>intended system, or some aspect of that behaviour. Hence, some prediction of
>how the brain would function under certain circumstances or more precisely a
>model of part of the brain's functionality. We can build a simulation of
>almost anything to predict its actions or model parts of it without the
>simulation being based on or being a replica of what we are modelling.
>Yusuf:
>In essence, saying the brain can be simulated is a bit of a hazy statement
>until the parameters are specified
Godfrey:
I agree that the brain cannot yet be simulated exactly as we do not
know how it works, but I do think that the simulation of the brain is
not a pointless activity. By simulating how we think the brain works,
we can see if the activity in our simulation matches that of a real
brain. By observing the differences in our simulations we can refine
our model, and maybe get closer to how the real brian works.
>> SEARLE:
>> The question is, "Is the brain a digital computer?" And for purposes of
>this
>> discussion I am taking that question as equivalent to: "Are brain
>processes
>> computational?"
>Yusuf:
>In essense, if brain processes are computational, then like computational
>processes in a digital computer, the brain becomes the digital computer that
>manages the effective execution of the required processes.
Godfrey:
If this were the case, would it mean that the mind is implementation
independent? We could then run the brain processes on a digital
computer, and surley the computer would be exactly equivelent to the
brain. I still do not think that it would have a mind as it would
still be perfoming meaningless symbol manipulation.
>> SEARLE:
>> It is clear that at least some human mental abilities are algorithmic... It is
>> furthermore a consequence of the Church - Turing thesis and Turing's
>> theorem that anything a human can do algorithmically can be done on a
>> Universal Turing Machine... Now it seems reasonable to suppose there might
>> also be a whole lot of mental processes going on in my brain nonconsciously
>> which are also computational. And if so, we could find out how the brain
>> works by simulating these very processes on a digital computer.
>Yusuf:
>Yes, but since only some of our mental abilitites are algorithmic and only
>some to many of the brain processes might be many, this goes to show us tha
>the brain is not a digital computer, at least not wholly. This is because a
>digital computer is basically only capable of performing computation
Godfrey:
I'm not sure what is being said here. I think that Yusuf is saying that
as only some of the mental abilities are algorithmic, a lot may not
be. So the brain is probably not a digital computer. Would modeling
these nonconscious activitys be of much use. They must at some point
interact with processes that are non algorithmic as we are consious of
the fact that we are thinking. If only a small part of the mind is made
from these algorithmic activitys, compaired with the rest of the brain
would they be able to provide us with enough information to make any
new discoverys from?
>> SEARLE:
>> We thus have a well defined research program. We try to discover the
>> programs being implemented in the brain by programming computers to
>> implement the same programs. We do this in turn by getting the mechanical
>> computer to match the performance of the human computer (i.e. to pass the
>> Turing Test) and then getting the psychologists to look for evidence that
>the
>> internal processes are the same in the two types of computer.
>Yusuf:
>Following Turing's thesis of Indistinguishability, we would therefore be
>able to deduce/assume that the human brain is a digital computer.
Godfrey:
Just because we cannot tell two machines apart, does not mean that they
are the same machine. An electric and petrol engine both are able to
power a car but they work in completley different ways. I think that
all we would ba bale to conclude from this test would be that, we
cannot differentiate between a brain and a digital computer
>> SEARLE:
>> Analogously, we might discover in nature objects which had the same
>> sort of shape as chairs and which could therefore be used as chairs;
>> but we could not discover objects in nature which were functioning as
>> chairs, except relative to some agents who regarded them or used
>> them as chairs.
>Yusuf:
>At the end of the day, chairs are things we sit on, so we do not need to tag
>an item "Chair" before in becomes a chair in the same way that a digital
>computer is or isn't
Godfrey:
I agree that the state of an object is not changed whether we label it
as something or not. But I think that the object can be interpreted as
a chair by the individual, and each individaul could have a different
interpretaion about what the object is.
>> SEARLE:
>> One beauty of this research program, often remarked, is that we do not need
> to know the details of brain functioning in order to explain cognition. Brain
>> processes provide only the hardware implementation of the cognitive
>> programs, but the program level is where the real cognitive explanations are
>> given.
>Yusuf:
>I totally disagree with this statement. We cannot be sure if the details of
>the brain functioning might have an indirect influence on cognition. To
>state that " we do not need to know the details of brain functioning in
>order to explain cognition" is like saying we do not need to know the
>weather in Alabama to predict the weather in Southampton.
Godfrey:
I agree with Yusuf. I don't see how this could possibly be true. We do
not yet know that cognition is not dependent on the architecture of the
brain. In Searle's chineese room argument, he shows that understanding
is not soley computation, but there is something else in our brian that
allows us to understand.
>> SEARLE:
>> The implemented program has no causal powers other than those of the
>> implementing medium because the program has no real existence, no
>> ontology, beyond that of the implementing medium. Physically speaking
>> there is no such thing as a separate "program level".
>Yusuf:
>I disagree, if i had a robot, the code implementation that makes the limbs
>move, aid speech etc are all causal. So this statement is exactly true,
>however a PC just running code isn't really causal apart from to the
>hardware.
Godfrey:
But surley the causal powers of the program running in the robot, are
all dependent on the implementing medium e.g. the robot. If it had no
limbs then the program would have no causal powers. A PC is not an
implemented program but a lumb of hardware, any program runnign on the
PC would have all the causal powers that the hardware allows it.
>> SEARLE:
>> In the brain computer there is no conscious intentional implementation of the
>> algorithm as there is in the human computer, but there can't be any
>> nonconscious implementation as there is in the mechanical computer either,
>> because that requires an outside homunculus to attach a computational
>> interpretation to the physical events.
>Yusuf:
>At what stage, was the differentiation between the brain computer and human
>computer made, because i must have missed it. And based on this, what
>exactly is this statement getting at?
Godfrey:
I am confused by this as well. Is Searle talking about the brain as a
piece of hardware and the human computer as the whole human? or is he
saying that the brain computer is the real brain, and the human
computer is a man made implementation. As it would make sence that we
have no conscious algorithm running in my head, but I would be
conscious of an algoritm that I had designed and written.
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