[Martin Taylor 970226 11:00]
Rick Marken (970225.2250 PST)] to Bruce Abbott
Perhaps this message will be seen as wilfully malicious. If so, I'm sorry,
but Rick posts such a tempting target sometimes, rather like a sniper
who stands in an open field to shoot his victims, instead of hiding
up a tree. Brave, but then ...?
The problem is that this sniper is a ghost or a vampire, that doesn't
even know when ordinary bullets pass through him. So I guess he's not
being so brave when he stands in an open field with his AK-47.
Two points: 1) the central problem in understanding the behavior of
a control system is determining what perceptual variables it controls.
This may well be true, but you usually seem to define "the central problem"
as "the only problem." You have asserted that it is illegitimate to seek
how these perceptual variables are produced (computed, learned, structured),
that it is illegitimate to look at how output systems may be organized,
that it is illegitimate to consider how "the controlled variable" changes
as disturbances change, etc., etc. The _only_ thing that may legitimately
be studied is _what_ perceptual variable(s) is/are controlled--not even
when, why, or how "what" changes.
We use the "control-system hammer" (The Test) becuase we are looking for
the control system nail (controlled variables).
Yep, and your buildings are not screwed down, nor are they glued. They
are all nailed, regardless of whether you are dealing with framing,
brickwork, plumbing, electric supply, or wallpaper.
2) conventional psychologists, wielding _only_
their causal sysem hammer (standard
IV-DV methodology) have never and will never discover the variables
organisms control; they will simply labor under the assumption that
they are dealing with a causal system, whether they are or not.
Depends what they are using the methodology for. No, they won't discover
the variables the organisms control, and they won't build a house, because
they won't have the framing on which the brickwork, the plumbing, the
drywall and the electric supply are hung.
So my hammer (The Test) is a hell of a lot better than yours
(standard IV-DV methods)
There's no "better" about it. Without your hammer, the building can't
even be started. Using only your hammer, it can't be finished. There's
a place for every tool. "They" try to use screwdrivers where hammers are
needed. Useless. You hammer screws into the brickwork. Pointless (the
screw is, after you've finished, at least).
> Rick, here is a component of a simple proportional controller:
> --------->[Perceptual Input Function]--------->
> Please identify the closed loop in this diagram.
There is no closed loop in this system so it would be perfectly
appropriate to study the perceptual input function using standard
IV-DV techniques -- as is done in physiological studies liek those
of Hubel-Weisel. I don't think the researchers in your "judgment" study
directly monitored the output of the perceptual input function, did
they? In fact, they used standard IV-DV methods to study
perceptual/cognitive processing in a closed loop system system.
Nope. What Bruce said was right, that the variable the subjects control
is a perception of satisfying the experimenter (probably--and along with
many other things). What, in most perceptual experiments, they cannot
control, is the pattern the experimenter provides as a "stimulus" for
which they are asked to judge some aspect and produce a "response". Their
"response" has no effect then or later on the "stimulus" they are being
asked to judge. If their responses are "good" in the experimenter's view,
they will thereby reduce error in the perception they are acting to control.
But the sub-part, or component, of that loop between "stimulus" and "response"
is itself appropriately studied by IV-DV methods, because it _is_ an
open-loop element just as Bruce sketched (though he omitted the part
from PF to muscle output, which might be important).
We went through all this some years ago, and I'm surprised (no I'm not)
that you have mindlessly reverted to "Om mane percepti Om".
You can't break intact organisms out of their closed loop
relationship with respect to their sensory inputs and study the
input-output relationships in the loop. Sorry.
Actually, in electronic/electrical systems there is a technique called
"clamping" that effectively breaks loops by ensuring that the signals
in one part cannot affect themselves. The dual of clamping (fixing
some voltage) is cutting the circuit (fixing the current at zero).
Same in psychological studies. A component can be studied by IV-DV
methods if the effects at the output cannot affect the values at the input.
What I will grant you is that these studies are very often misapplied
when brought into the real world.
> Every component of a closed-loop, negative feedback control
> system can be viewed as an input-output device...As such these
> components can be quite properly analyzed using ordinary IV-DV
Yes. As long as you study these functions in an open loop situation. The
organisms in conventional psychological experiments are typically _not_
in an open loop situation; their sensory inputs influence what what they
do WHILE what they do influences their sensory inputs.
I don't know what you mean by "conventional psychological experiments."
Certainly not psychophysics, which is ordinarily open-loop as described
above, though some psychophysics is done deliberately closed loop--I've
done a lot of it that way myself in my younger days.
For example, I studied the motion after-effect by giving people control
over the speed of, say, a rotating disk, and asking them to keep its
rotation speed at zero (or some other prespecified value), after they
had looked at one they couldn't control rotating for some period of time.
I thought that was conventional psychology, and the journals to which I
submitted the articles seemed to have no problem with this view.
And when I asked people to say whether a particular time-interval had
or had not contained a tone, that was open-loop so far as the connection
between the waveform and the yes-no button push is concerned. Conventional
psychology, _and_ compatible with PCT.