Is the Brain a Computer?
Philosophy of Mind
BRENT SILBY
Unlimited (UPT)
Is the brain a computer?
How does a computer work?
Two types of computer…
1. Sequential digital processing
2. Parallel processing
Sequential Digital Processing
Computers used to be single, sequential processors
They performed only one task at a time. They appear to be multitasking
because they perform tasks extremely quickly.
To solve a problem, a sequential processor will treat the problem as
a number of steps that are followed in sequence.
Dual core CPUs can perform 2 tasks at once, so they are faster
Are brains (or minds) sequential processors?
We do operate in a sequential manner. We calculate math problems
in a step by step manner.
Even our communication is based on a sequential system. Sentences
can be broken up into symbols, which are interpreted according to
a sequence of rules.
Problem with Brain as a sequential processor
Neurons are incredibly slow compared to the switches contained on
a CPU.
A CPU switch can flip/flop from 0 to 1 in about 1 hundred thousand
millionth of a second--VERY FAST
A neuron takes about a thousandth of a second to flip in response to
input--VERY SLOW
So a brain neuron takes 100 million times longer to do the same
thing a CPU switch can do.
THE 100 STEP LIMITATION
* Suppose that the brain works by following a sequential program
like a computer (i.e. by following one instruction at a time in a
program)
* Because of the speed of neurons, the maximum number of instructions
a brain can carry out in a 10th of a second is 100.
* It takes only about a 10th of a second for the brain to extract the
meaning from a sentence.
* It follows that if the brain is following a sequence of instructions,
then it would only take a program of 100 instructions for the brain
to gain meaning from a sentence.
BUT, This is an incredibly small number of instructions in a program.
A simple PACMAN game requires a program of
1000 lines of instructions.
Current Artificial Intelligence programs contain over 1,000,000
lines of code (or instructions).
We must conclude that whatever the brain does, it is not following
a list of instructions (or program) one step at a time.
How can the brain do everything it does so quickly?
Parallel Processing !
A Parallel Processor is a type of computer that carries out many
instructions simultaneously.
Imagine that I have 40 jars, and hidden underneath 1 of those jars
is a $20 note.
A sequential processor would search for the note by checking
one jar at a time. This is how a search engine works.
A parallel processor would would check under every jar at the same
time. This is very fast and efficient.
Its like having 40 single processors all working at the same time.
* There is no real difference between what a sequential processor
and a parallel processor can do.
A sequential processor can do everything that a parallel processor can
do. It just breaks the process down into a step by step, one instruction
at a time procedure.
If this is true, is it possible to build a sequential computer that can
simulate the brain? [discuss]
Perhaps, but given the number of connections in the brain, it would
take a modern computer several years to do what a brain does in just
one second !
How brains and computers remember things…
* Memory is vital to computers
* Memory is also vital to brains
* In a computer, bits of information are stored in specific locations
either in RAM, CD, DVD, Flash, or Hard-drive.
These locations have specific names. Information can be retrieved
when the program looks up a certain name and checks the content
of that location.
In a brain, there are no such locations.
You cannot point to a specific place in the brain and say
“this is my memory from 10pm last Saturday night”.
The brain is not like a video camera, and does not record information
completely and store it in certain places.
When events happen, they have an impact on the neural structure of
the brain.
For example, at a party on Saturday night at 10pm this happened:
* A song called “Show me love” was playing
* Someone spilled beer on me
* I could smell hot chips
Each of these things effected my brain and set up a connected
neural structure.
* The song set up a neural pattern in my auditory system
* The wet beer set up a pattern in another sensory system
* The smell of hot chips set up another pattern
These patterns are all connected through a neural link.
Now, when I smell hot chips, that will re-activate the previous
neural pattern, which is connected to the others which are also
re-activated.
That’s why when I smell hot chips, it makes me think of the song
“Show me love”. The memory of that event is stored everywhere
in the brain.
BUT,
The memory is not permanent.
The neural connections will weaken if not used, and the memory
can fade.
On the other hand, if the memory *is* used, then the memory will
strengthen.
WARNING! Memory will become unreliable with time. Whenever
it is retrieved, there is risk that it will be associated with other events
since they create connected neural patterns.
Human memory is extremely unreliable.
e.g. of violent crime victim in court
e.g. of crime victims testifying years after event took place
Despite its unreliability, human memory allows human creativity
This is because of the way certain ideas trigger memories, and
connections with other events.
Human brains are associative engines. Its all about building
associations.
Computer software is implemented on sequential hardware
The mind is implemented in the parallel processing,
connectionist brain network
But the mind doesn’t feel like it’s a parallel processing, connectionist
device.
Think about day-to-day experiences. It feels like our mind is a
digital/sequential system.
WHY?
• The brain is a parallel processing computer, which is built from
a connectionist network
• The mind is a sequential program, which is implemented upon the
brain’s parallel hardware.
This is possible through language !
Language is a sequential system that is installed on the connectionist
hardware of the brain. It allows the brain to operate as a sequential
system.
So, is the brain a computer?
Yes, it’s a parallel processing connectionist device.
The mind is a sequential software that operates in the brain.
It is installed slowly through the acquisition of language.
Now, the big question…
Can a brain be *conscious* without a mind? Or is a mind essential
for consciousness? If so, then according to the above hypothesis
language is essential for consciousness.
Powerpoint by BRENT SILBY
www.def-logic.com
Produced at UPT
Christchurch, New Zealand
www.unlimited.school.nz