[From Bruce Abbott (950526.2000 EST)]
Rick Marken (950526.1520)
Well, you [Bill Powers] think that Bruce's description is not useful. I
think that Bruce's
description is not useful. But it seems that Bruce (950526.1410 EST) thinks
that Bruce's description IS useful. In fact, I haven't been able to detect
much change in Bruce's position on this matter since he got on the net.
Given the redundancy here, that counts for only one opinion, so the score is
one to one. And you're right, I haven't changed my position on this matter.
Why would I want to change it from right to wrong? (;->
Bruce seems to be controlling for the idea that descriptions of the
appearance of behavior from the point of view of a human observer (the
typical way behavior is described in the behavioral sciences) should be
accounted for by PCT. We keep explaining (and demonstrating) why it is
impossible to do this. It is because it is impossible to tell what variables
are being controlled by simply looking at behavior; descriptions of behavior
are, therefore, not particularly useful to PCT.
And I keep explaining why I think they should and can be--and how. I've
never heard you try to knock down my argument, or even note it. You seem to
prefer to just ignore it and reassert your own position. It's a rather
peculiar way to "argue" and, from my position, unconvincing.
How about stating, just for the record, what my argument was? (You can
paraphrase if you like.) I'd like some proof that you read it and
understood it, even if you disagreed. Then maybe we can discuss whether it
has merit.
In his brief post on "describing fly behavior", Bill Powers (950526.1230 MDT)
explains why Bruce's description of fly behavior provides no picture at all
of the fly's "basic strategy". The fly's basic strategy is to control its own
perceptions. Bill's post explains why Bruce's description of how a fly lands
on the ceiling is more of a fantasy than the PCT version that I invented.
I suppose when your kids ask you how to do something you just tell them to
control their own perceptions. I'll bet they're pretty perplexed.
I was, of course, describing what the fly does from the observer's point of
view, with (as I'm now saying at least for the second time) some additional
information about perceptual variables thrown in to help guide speculation
about how the control systems involved might operate. People have
speculated whether the fly does an inside loop (touching the ceiling at the
top of the loop) or a half roll in order to position itself legs up and
parallel with the ceiling. As I explained, neither suggestion is correct.
The way the fly does it I called a "strategy," but by that I do not mean a
conscious (or for that matter unconscious) plan that the fly is following,
only which of several alternatives actually occurs.
Bruce:
you really should take a look at some of this insect research. In this
field, at least, the "real, systematic, PCT data collection" seems to be
much more common than you seem to believe.
Why not help out and post some examples. That's what the net's for, no?
You mean in addition to the Nachtigall and Dethier book references I've
already posted and my general suggestion to take a look at the _Journal of
Experimental Biology_? How specific do you want?
I have been on the lookout for PCT type research for years.
Try looking somewhere else. The library would be good. (;->
In the last month,
there are suddenly two studies (the Science catching article and the
Srinivasan bee study) that are models of PCT research. This is QUITE unusual.
Our library is closed so at the moment I can give you only the small bit I
happen to have on my desk. How about:
Kittmann, R. (1991). Gain control in the femur-tibia feedback system
of the stick insect. _Journal of Experimental Biology_, _157, 503-522.
Preiss, R., & Gewecke, M. (1991). Compensation of visually simulated
wind drift in the swarming flight of the desert locust (schistocerca
gregaria). _Journal of Experimental Biology_, _157_, 461-481.
Spork, P. (1994). Adjustment of flight speed of gregarious desert
locusts (orthoptera acrididae) flying side by side. _Journal of Insect
Behavior_, _7_, 217. [I haven't seen this one yet.]
I could give you another half-dozen or so from the reference sections of the
first two articles, but you'll have them when you get these articles. Our
library is rather underfunded (each year more journals get cut); even the
_Journal of Experimental Biology_ is not longer being subscribed to here, so
I'm a bit stuck for the most recent references.
You claimed that Nachtigall "clearly recognizes that the structures mediating
insect flight are organized as perceptual control systems" but then presented
evidence (the description of how a fly lands on the ceiling) that he really
doesn't. So if there is some "real, systematic, PCT data collection" in the
insect research field, please point it out. But the "fly landing" stuff is
clearly not it.
Here's Nachtigall's description:
The fly approaches the ceiling obliquely from below, at a steep angle, at a
speed of about 25 cm per second. It then flies straight into the ceiling,
and shortly before striking it, stretches out all three pairs of legs. The
fore pair take up a special attitude, held out stiffly upwards so that they
are the first part of the fly's body to make contact. Held in this way they
act as shock absorbers and as anchors, adhering at the point of contact by
means of their claws and pulvilli (hairy pads). Simulatneously the wings
stop beating. Now the fly is clinging firmly to the ceiling with its fore
feet, but its body still has a certain forward momentum. Like a flywheel on
its shaft the fly rotates about its fore feet and turns its belly upwards,
grasping the ceiling with its middle and hind feet--and there it is, sitting
upside down on the ceiling, without having had to fly upside down first.
Nachtigall, Werner (1974). _Insects in flight_. New York: McGraw-Hill.
p. 119.
This was all determined via high speed photography, is purely descriptive,
and is irrelevant to the issue of Nachtigall's understanding of control
system theory--and to mine.
Why don't you have a look at this book, Rick, and judge Nachtigall's
understanding for yourself? I'll bet they've got it at the UCLA library.
Heck, even OUR little library has a copy!
Regards,
Bruce