[ExI] Do digital computers feel?

[Ben]

Brent, you'll probably ignore this as you have my other posts on this 
subject, but I think these things still bear saying, as there are 
spectators to all these conversations, and while a bit of light-hearted 
bantering about how many angels can dance on the head of a pin is fine, 
I'm uncomfortable about letting people think that most of us actually 
believe in angels in the first place.
That was a metaphor, by the way :D

What I mean is, I have to take issue with the basic assumptions you make 
in your arguments. e.g.:

"If you strip away all the memories of red, and you strip away all other 
information, such as yourself perceiving it, and so on, you are left 
with just plain and simple redness"

That makes as much sense as saying that if you strip away all the cogs, 
springs and levers in a clock, you are left with just plain and simple 
time-telling. In other words, none.

It's the memories and perceptions that /create/ redness. Nothing 'plain 
and simple' about it. This is the fundamental mistake that I think you 
make: Assuming that complex, combinatorial phenomena are actually 
'fundamental properties'. They are not, and I don't see any way they 
possibly could be. If they were, it would be possible to demonstrate 
their existence outside of a human mind. Can you show that 'red' exists 
outside a human mind?

Aside from that, you do tend to make various simple mistakes of fact. 
e.g. in Vol 160, Issue 3 you write:

"The perception of a strawberry starts with the target of perception or 
the surface of the strawberry having a set of physical qualities, (it's 
ability to reflect something like 650 NM light) that we think of or 
interpret as being "red".  There is the causally downstream set of 
physical qualities which are very different from the set of physical 
qualities the surface of the strawberry has. This is the 650 NM light."

Fair enough so far (apart from the equivalence of 650nm light with 
'red', but read on), but then you say:

"Then, there is a translation mechanism (the retina) which translate the 
physical qualities of the light into a different set of physical 
qualities (the red and green signal traveling down your optic nerve)"

The crucial point here is that /there are no red and green signals in 
the optic nerve/, in the way there are, say, 'red' and 'green' colour 
codes in a computer. Neither is 650nm light the same thing as 'red'.

There is in fact no neural representation of 'red' in our optic nerves.  
If you took an axon at random from the optic nerve, and recorded the 
signals travelling down it, there is no way you, or anyone else, could 
tell if it was signalling the presence of a red-green, luminance, or 
blue-yellow colour channel (there's no such thing as 'red', 'green', 
'blue', etc., signals as such, in the visual system. Search on "colour 
opponent theory" for details), or a light patch in the left field of 
vision, a dark patch in the right field, an edge at 65 degrees, or 
indeed any kind of meaningful visual stimulus, without also knowing a 
lot more about how it's connected.

At this stage of our perception, the concept of 'red' /does not yet 
exist/. This is a crucially important fact, because it shows that the 
perception of 'red' is not seamlessly and rigidly connected to a 'red' 
object (meaning something that reflects ~650nm light) in our field of 
vision. There's a very simple experiment you can do to confirm this. 
Take a red object outside at night and look at it under moonlight. Is it 
red? No? OK, maybe that's because the moon doesn't reflect any 650nm 
light (do you really think this is true?), so let's try a different 
colour. How about a yellow object? Blue? Green? Can you see what I'm 
getting at? We don't /perceive/ something like 'red', it's more that we 
/create/ it, in our minds, from a complex set of inputs, including but 
by no means limited to, what comes in through our optic nerves.
Here's another example. If you have a white object, and look at it 
through a pair of spectacles with a red filter in one eye, and a blue 
filter in the other, what colour is the object?

The only way of making sense of the signals in the optic nerve would be 
to map exactly where an axon comes from and goes to, because visual 
information is coded by something called 'line-labelling', where the 
meaning of a signal is entirely dependent on what it's connected to. If 
you took an axon that normally conveys the presence of, for argument's 
sake, a dot of red in the centre of your right eye (as I've said, it's 
not that simple, but never mind), and connected it to a slightly 
different part of the lateral geniculate nucleus of the thalamus to the 
one it normally synapses with, then that signal would mean something 
totally different. It could even mean a sound or a stab of pain in your 
leg, if it was moved so as to synapse with a neuron just a few 
millimetres away from its original target. And it makes not a jot of 
difference which neurotransmitter caused that neuron to send a signal 
down its axon. Not does it make a jot of difference which 
neurotransmitter it releases at its axon terminals, to the meaning of 
the signals that the downstream neurons convey. In fact the 
neurotransmitters, as I've alluded to in a previous post (and as Stathis 
points out), are kind of irrelevant. They are just signals, and what 
they convey is /completely independent of what they are/, rather like a 
1 and a 0 in a digital computer. "What does 1 mean?" Silly question, 
isn't it? Ditto "what does glutamate mean?". The meaning is totally 
dependent on the context. In our brains, that context is whether the 
receiving neuron is positively or negatively polarised by its glutamate 
receptors, and which other neurons it synapses with. Replace glutamate 
with something else, and make the receptors correspond, and there will 
be absolutely no difference. You will no doubt disagree, but I insist 
that /glutamate on its own means absolutely nothing/. Science tells us 
this, and if you disagree, you're not just arguing with me, you're 
arguing against science.

Philosophising about our minds is all very well, but it really does have 
to start with some basic neurobiology, or it's totally meaningless. I'm 
no expert in sensory neurobiology, but I know enough about it to see 
that these ideas about red qualia etc., that you propound, are totally 
orthogonal to the known science about how our minds work. But I can also 
see that you're trying to convey /something/.

So, the challenge is: Can you reformulate your arguments in line with 
the known science of how the brain works? No more 'fundamental redness', 
no more 'glutamate is red'. Stick with the science, and maybe we'll 
understand what you're actually trying to say.

Ben Zaiboc