[From Rick Marken (960921.0920)]
Rupert Young (960920 1100 BST) --
Welcome to CSGNet, Rupert.
Bill Powers (960920.0900 MDT) answered two of your three questions; I'll
take a shot at the one he didn't answer:
a) How does HPCT's approach to animal systems, of hierarchical levels of
control, conflict with conventional psychology ?
The basic conflict is captured by the title of Bill's book: _Behavior: The
control of perception_. Conventional psychology is based on the idea that
behavior (actions and the results of those actions) is ultimately caused by
perceptual inputs. The title of a book about the conventional psychology
approach to animal systems could be: _Perception: The cause of behavior_.
(Some conventional psychologists, like J. B. Watson and B. F. Skinner,
might take an even stronger stance and call their book _Perception: The
control of behavior_. In this case it is the perception of a _reinforcer_
that controls behavior).
Even modern cognitive science and complex systems approaches to behavior
are based on the idea that behavior is _caused_, though not necessarily by
perception. In cognitive science the causes of behavior are "goals" or
"plans" in the brain. In the complex systems approach, behavior is defined
by differential equations that describe causal relationships between many
variables; the equilibrium state of this system of equations is the "end"
or "goal" of behavior: behavior is again the end result of a causal
In PCT, behavior is not an effect that is caused. Rather, behavior is a
process: the process of _controlling_. PCT starts with the observation that
the term "behavior" is ambiguous; it refers to both actions and the results
of those actions; to flapping wings (action) and flying through the air
(result). PCT also recognizes that organisms are not the only cause of the
results of their actions; the results of action are also caused by
environmental variables (disturbances) that are quite unpredictable. For
example, flying is caused not only by flapping wings but also by air moving
at a particular speed and angle relative to the wing. Despite these
disturbances, organisms act to produce consistent results; the bird flies
despite continuous variation in the speed and angle of the wind relative to
its wings. Organisms do this by adjusting their actions _as necessary_ to
produce the intended result; the bird adjusts the flapping of its wings to
produce exactly the lift needed to fly. The process of producing consistent
(intended) results in the context of variable disturbances is called
_control_. It is also called _purposeful behavior_. Organisms control by
acting to bring a perceptual representation of the intended result into a
match with an internal (to the organism) reference specification for that
result. Behavior is the control of perception.
The process of control is not a cause-effect process; control occurs in a
loop where every variable is both cause and effect at the same time.
Nevertheless, control can _look like_ a cause-effect process when viewed
from outside the behaving system (see my paper "The Blind Men and the
Elephant" which is available on the Web via the CSGNet References section).
Basically, the mutual (and necessarily correlated) effect of disturbance
and action on an intended result (controlled variable) gives the illusion
that external events (distubances) cause responses (actions). The
conventional approach to understanding behavior is based on the assumption
that this disturbance-action relationship reflects the existence of a
causal path through the organism, from environment to perception to
"behavior" (response or action). The PCT approach to behavior shows that
the existence of this causal path is an illusion. This is the basic
conflict between the conventional and PCT approaches to behavior.
Unfortunately, it is not a conflict that can be resolved by compromise; if
organisms are control systems, then the conventional approach to
understanding behavior "has been in the grip of a powerful illusion since
it's conceptual bases were laid" (Powers, Science, 1973). This is
obviously something, up with which conventional psychologists will not put;
hence, the overwhelming lack of interest in PCT since the publication of
_Behavior: The control of perception_.
What all this means for HPCT is that hierarchical models based on
cause-effect principles (Albus has one; Brooks at least talks about his
this way) are fundamentally different from HPCT; they are based on the
hierarchical generation (cause) of output (actions). HPCT is based on the
hierarchical control of input (perception). To get an idea of how an HPCT
model work, see my paper _Spreadsheet analysis of a hierarchical control
system model of behavior_ which is available on the Web as one of the
chapters in my _Mind Readings_ book.