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- Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU
- Subject: (no subject given)
- Path: sparky!uunet!paladin.american.edu!auvm!FAC.ANU.EDU.AU!ANDALING
- Message-ID: <9208190230.AA07131@fac.anu.edu.au>
- Newsgroups: bit.listserv.csg-l
- Date: Wed, 19 Aug 1992 12:30:35 EST
- Sender: "Control Systems Group Network (CSGnet)" <CSG-L@UIUCVMD.BITNET>
- From: Avery Andrews <andaling@FAC.ANU.EDU.AU>
- X-To: csg-l@vmd.cso.uiuc.edu
- Lines: 71
-
- [Avery Andrews 9108191231]
-
-
- (penni sibun 920818.1200)
-
- >maybe someone can explain this to me. when you say ``signal'' or
- >``variable'' or ``percept'', it has connotations to me of a unified
- >thing, like a tone, or a light intensity. but when i look at the
- >road, i am not perceiving something like a tone. if you can explain
- >how all the stuff my eyes take in can be a single unified thing, maybe
- >i won't find it so oversimplified.
-
- With a sonja-like visual system, one might set one marker to tracking
- the hood-ornament, another the center line of the road, & let the controlled
- perception be the distance between them (or so I guess--having never
- built a sonja-like visual system, I don't have full faith in my
- intuitions about them).
-
- On the general subject of the supportiveness of the environment, I
- suspect that the difference between PCT & c&a-style interactionism
- might be more one of rhetorical emphasis than substance. PCT in
- fact depends very much on the fact that many (in fact most, by an
- overwhelmingly large margin) features of the environment can be
- leaned on. A steering subsystem would for example depend on all sorts
- of facts about roads and carparts about which it knows nothing, as
- well as upon the workings of the lower-level control-systems it
- works through. To perform at a minimal level, all that it has to `know'
- is the relationship between change in torque-applied-to-the-wheel to change in
- relationship-between-hood-ornament-and-centerline-markers (of course,
- for hi performance, lots more is needed, but the extra knowledge isn't
- about car parts, etc.).
-
- One theme of c&a interactionism, as I hear it so far, is that you
- don't have to know very much to get by -- keeping your eye on the
- situation and following a few simple rules is enough. PCT claims that
- you can say a bit (or maybe a lot) more than that, in particular,
- something about the general nature of the kinds of rules that will in
- fact suffice to get you by -- that on the whole, they tend to be such
- as to keep perceptions ( = the output of `registrars') at particular
- values, or at least within particular ranges of values. The claim is
- that architectures that don't do this won't work. I would take this
- claim to be decisively refuted if someone built a robot vehicle that
- did stay on the road in an interactionist manner, but just because it
- was `the easiest thing to do', without containing anything remotely
- like a control system controlling a perception along the lines of
- `position-of-vehicle-relative-to-the-road'.
-
-
- It remains to be seen if this is a `golden thread' that will be the
- indispensible key for untangling or building these systems, or if it is just
- one of a dozen rules of thumb for doing so. It does so far seem to me
- to be a useful organizing principle that is absent from c&a (but for all
- I know, this could be only because they think it's so obvious that it
- isn't worth mentioning). And it also remains to be seen if, when
- applied complex systems, it will apply cleanly, or instead grow so much
- hair that it will get difficult to discern the original beat under the
- fuzz.
-
- For example, whatabout the little positive feedback loop in the
- beerbug's feeding controller (based on the supposed wiring of the
- infamous Aplysia). What goes on here is that if the bug is hungry
- enough (the energy level is far off enough from its reference level)
- and over food, it will start eating, but being eating also excites
- the feeding controller, so it keeps eating even when its energy level
- is no longer low enough to successfully trigger eating. The whole
- system can be regarded as (part of) a control system for the maintenance
- of energy-level, but the positive feedback loop looks like at odd bit
- stuck in.
-
-
- Avery.Andrews@anu.edu.au
-