[From Rick Marken (981105.1050)
Bill Powers (91105.0420 MDT)--
I'd just forget about "the" control hierarchy, when dealing with
a specific real system. We can see how a temperature control system
might work through specifying reference levels for a statocyst-touch
control system, and that would be sufficient to account for the
observed behavior of the slug. If you can see how that works, why
do you need to name the levels?
I agree completely.
Sometimes I regret ever producing that list of names. It seemed
like a good idea at the time.
I think it was (and still is) a _great_ idea. Your hypothetical
hierarchy has provided some real "value added" to the basic PCT
model. For example:
1. It shows how, _in principle_, a control of input system can
account for the kind of complex behavior we have experienced "from
the inside" (we are familiar with our own control of perceptions
of relationships, like marriage, principles, like fairness, and
system concepts, like "American") and "from the outside" (we see
that others seem to be controlling for these complex perceptions,
too). So the hierarchy adds value by showing the _feasibility_
of a control model of _all_ behavior.
2. It gives people a description of the kinds of perceptual variables
that they can experience and become aware of as controlled variables.
I know that my own understanding of PCT increased significantly when
I became aware of the variable sequences, relationships, programs,
principles and system concepts that were part of my own perceptual
world. So the hierarchy adds educational value.
3. It suggests hypotheses about the kinds of variables people
might control. The design of my own little "Hierarchy of Perception
and Control" demo/experiment at:
(which works extremely well on my Mac G3 running Netscape 4.5) was
helped by your notion that the perception of a _sequence_ is not
the same as the perception of a _motion_ (which, in the demo, is an
illusion created by showing a rapid "sequence" of configurations).
So the hierarchy adds value by suggesting research hypothesis.
Unfortunately, the hierarchy has created some problems as well.
Actually, I can think of only one problem it has created:
1. It gives people -- especially those who are not inclined toward
observation -- the impression that the perceptual hierarchy
(intensity, sensation, transition, relationship, etc.) _is_
the PCT model. This leads to the "How many angels can dance on
the head of a pin?" sort of discussions about "where the X level
should be located" or "whether there should be a level between
level Y and Z".
I think the "value added" by the hierarchy far outweighs this
I don't regret that you produced the names of the perceptual
levels that make up the hierarchy. Once one gets out there and
starts looking at the phenomenon of control (from the outside
and/or from the inside) one quickly learns to treat the proposed
names and hierarchical arrangement of the levels as what they
are -- a helpful heuristic.
Richard S. Marken Phone or Fax: 310 474-0313
Life Learning Associates e-mail: firstname.lastname@example.org