Ain't Miss-bee-havin'

[From Rick Marken (950525.1045)]

Bruce Abbott (950525.1100 EST)--

The point I was making was in response to Rick Marken's short question
"Signalus-response?" which asks whether I was offering an S-R interpretation
of the effect of foot-pad pressure shutting down the bee's flight motor. My
point was that without data one could offer all sorts of "glib explanations"
(as I then illustrated).

I don't think you got my point. You said:

The signal to stop flying comes from sensors on the foot pads.

This is an S-R description because it takes account of only one half of the
actual relationship between variables. If it is true that sensor signals from
the foot pad have an effect on the wing movements that produce flying, then
it is also true that the wing movements that produce flying have an effect on
the sensor signals from the foot pad. There is a closed loop of cause and
effect that goes through the environment. The existance of this closed loop
could not possibly be determined by looking at just the wiring diagram of the
fly. It is a fact that exists because of the nature of fly's relationship to
its environment. Even if there is an S-R relationship between sensory and
effector neurons in an organism's wiring diagram, the organism is still an
input control system (with a fixed and implicit reference for the input) if
the effector neurons have a negative feedback effect on the inputs to the
senrory neurons via the environment.

Now assume that I had the fly wiring diagram spread out before me and wanted
to know whether the footpad signal that ordinarilly stops the fly's flight
motor represents a perceptual variable in a control system or an open-loop
shut-down command signal. So I examine the diagram, looking for the sensory
feedback loop required if the footpad signal is part of a flight-motor speed
control system.

You can't see the kind of feedback loops we deal with in PCT by looking
just at a wiring diagram. A perceptual control loop goes through the
environment so a wiring diagram alone will tell you absolutely nothing about
the nature of the system -- whether it is open or closed loop. In order to
determine whether a system is a closed loop control system (by inspection
rather than by doing The Test) you would have to determine whether the
efferent outputs of the wiring diagram have an effect, via the environment,
on the afferent inputs to the circuit; so you have to inspect the circuit
AND its relationship to the envionrment.

The diagram would tell me whether the system is open- or closed-loop.

You might find internal feedback loops in the circuit diagram but you will
not be able to tell whether or not the circuit exists in an open or closed
loop relationship its the environment by just looking at the circuit.

An interesting example of mistaking a control system for an S-R system based
on looking only at the "wiring diagram" occurs in analysis of the "Vehicles"
models developed by Braitenberg (sp?). These are simple little software
systems that move around by producing output forces in response to sensory
inputs. I have seen these Vehicles described as "S-R" systems in journal
articles about mobile robots.

The S-R designation for these Vehicles is based on an examination of their
internal architecture; they do produce outputs in response to inputs. But
their inputs are also, at least in part, a response to the outputs. So
these systems live in a closed loop; they have fixed, implicit reference
signals set to zero and they are dynamically stablized by integrations in the
output function. These Vehicles are actually control systems that control
their input - - which is proven by the fact that they will protect their
input (like the perception of target intensity) from disturbance (such as
movements of the target).

The people who study these systems seem to have no idea that they are dealing
with input control systems -- even though they know every detail of the
"wiring diagram" of the system.

Best

Rick