[Martin Taylor 960627 16:30]
Jeff Vancouver 960627.14:45 EST
It should not surprise me that I cannot predict Bill P. response to
things. But I guess that is because we don't actually predict :).
Anyway, I was expecting that he would find this statement comforting.
I, too, found it hard for many months to "feel" what Powers et al would
find distressing in various statements (I still do, when it comes to
"information" :-). I think you are at the same stage now. When I read
what Bill quoted, it horrified me, too, well before I read Bill's
(now) predictable reaction.
The key problem is not just the phrase "a plan emerges." It's much worse
than that, though that's bad enough. It sounds as if, and there's no
evidence to the contrary, the authors think that if the "brain" plans
a set of muscle movements, then the right things will happen in the world.
They won't. (Unless the person normally wins the lottery every week, too).
The whole structure starts at the wrong point: "Sensory systems capture..."
They do, to be sure, but what is it that they "capture"? And how is what
they capture _primary_? What matters for making a toast is, say, a
wish that a toast be made _compared with_ a perception that it has not
been made; from that a wish that glasses be charged _along with_ a perception
that they are/are not; from that a wish that there be a wine bottle in
hand and pouring...(I elide a lot of stuff, here); from that a wish to
perceive certain muscle tensions...(I use "wish" as a neutral term, trying
to avoid "goal;" it's not supposed to mean anything conscious).
All of this varies, not as a consequence of fulfilling "the plan", nor
as responses to stimuli, but as _control_, acting blindly at each level,
in one of many ways that could possibly achieve the references coming
from a combination of _many_ wishes of different kinds (e.g., to be perceived
as fashionable, to see oneself as neat and not clumsy, to perceive a
formal sequence--of toasts--as being followed,...). The next time that
the "same(!)" thing happens, how much of that do you (or Lipon) think
would be reproduced? How many of the "neural signals" would be even
close to repeatable?
Now it is (subjectively) clear that we do make plans. At least, I perceive
myself as doing so. I think, speculatively, that one is observing one's
program level control at work when one perceives oneself to be planning.
But I don't think that what the quote refers to has much to do with this
kind of planning. And it DOES have a lot to do with an S-R view of how
things happen, as well as a planning view. And that's the wrong way round.
You say this is all very like PCT. Well, let's think about a buildable
hardware control system of one level. It is true that the sensor "observes"
the external variable (say, shaft rotational velocity), and delivers a
current proportional to the value of the variable. It is true that this
current is compared with a reference value. It is true that the difference
is applied to the input of an amplifier/integrator (or something) whose
output affects the torque on the shaft, and it is true that the effect of
the output is to change the shaft velocity. All these things are true. But
do they tell you what is _happening_ here?
To argue that a listing of the S-R links in a causal loop will describe
what happens in the loop is like arguing that a listing of the chemical
constituents of my body describes me. All of those S-R links are there,
and are presumably correctly described. But to list them, and to list
them in _that_ order, is quite misleading.
In analyzing the control loop, you've got to go THE OTHER WAY ROUND.
Let's take an ordinary loop, like the shaft controller, and put some names
on the variables and functions:
v: shaft velocity
p = P(v): current output by the sensor (perceptual function).
r: reference sensor current
e = r - p: deviation of actual current from reference sensor current
o = O(e): output torque applied to shaft.
d: torques applied to the shaft from elsewhere.
and now again
v = V(o, d): the function relating shaft velocity to output and disturbance.
Now we've listed what Lipon lists (and a bit more). Have we described what
is happening? No way.
Let's try to describe what is happening. We can start anywhere, but the
two places most likely to be useful are v and p, because those are the
ones that will be stabilized most by the control system.
Starting with p, then. What do we know? We know p = P(v). Ah, we have
to deal with v, now. What is it? v = V(o, d), which now tells us that
p = P(V(o,d)).
We know nothing of d, so we have to leave it there. We do know something of
o, though. It is O(e) = O(r-p). And that means that we have p = P(V(O(r-p),d)).
This determines p as closely as we can, because r comes from elsewhere
and d comes from elsewhere. Given those two independent variables, p is
defined in terms of itself--something that simply doesn't show up in
the listing of S-R links, and something you can't discover except by blind
chance going the "forward" way around the loop. I mean, after all, to do
it the other way round, you've got p, and now you have to ask "Is there
any function in the neighbourhood that uses p." And in a hierarchy there
are lots of such functions (higher-level control systems' perceptual input
functions). You have to be plain lucky to find the one that's _really_
Of course, in going further, with realistic functions, you have to take
into account that these functions are all extended over time. None of
them output values based only on the current value of their input.
Past values also enter into all the outputs, and you have to treat those
time dependencies when you try to solve for what p will look like. This is
another reason for going "backwards" around the loop. Going backwards, you
are using events that have happened and are accessible within the system.
Going the "natural" cause-effect way around the loop, you are projecting
into the future, and things just might not happen as you expect.
But the point I'm trying to get across is that the analysis starting with
"Sensory systems capture..." is not wrong. It's misleading and gets you
nowhere in figuring out what's happening.
And that's why I found Bill's reaction utterly predictable. Though I might
have made the right prediction for the wrong reason:-)