From Bob Clark (930822.8:00 pm EDT)
Additions to and modifications of the Original "Portable
Demonstrator" were presented Sunday morning, August 1, 1993. The
summary and discussion is in several parts, to be posted as prepared.
I. PRESENTATION. Observer's View. "DEMO I, PRESNTATN - RKC"
II. COMMENTS. Demonstrator's View. "DEMO II, COMMENTS - RKC"
III. DISCUSSION. Experimenter's View. "DEM III, DSCUSSN - RKC"
IV. TEMPORAL VARIABLES. Various Views. "DEM IV, TEMPORAL - RKC"
V. SKILLS. Various views. "DEM V, SKILLS - RKC
III. DISCUSSION. The Experimenter's Viewpoint.
Introduction. Each of several controlled variables is displayed,
together with related time delays that can be regarded as "reaction
times." Perceptual variables composing controlled variables is
identified. In addition, the organizational relations among these
variables is displayed.
This form of demonstration, the "Portable Demonstrator," arose soon
after we realized that human activity could be described in terms of
the operation of a large number of individually simple negative
feedback control systems. Clearly, these control systems required
some form of organization to result in coordinated actions. This led
to the concept of a hierarchical structure, with the higher level
achieving its purposes through setting suitable, selected, reference
levels for an assortment of lower level systems. Our approach to
analysis of the postulated hierarchical structure was "from the
bottom up," beginning with readily identified and available systems,
namely the skeleto-muscle systems. This moved upward, adding further
systems as needed, trying to keep any additions to a minimum, and,
even then, seeking to work with identified neural pathways that,
later, were recognized as carrying "perceptual signals."
At that time we were very interested in identifying and labelling the
various levels as they were then perceived. This process
("identifying and labelling") has continued over the years, with the
objective of providing a structure that could encompass all --
certainly "very nearly all" -- human behavior. This objective has
not yet been fully achieved, but the effort is continuing.
For convenience of discussion, the specific names (for levels)
suggested in Part II are continued. Others are added as needed.
Numerical levels are not assigned at this time.
A. MUSCLE TENSIONS. Here the controllable variable consists of the
set of muscle tensions required to position the hand-arm assembly.
The perceptual variables, confirmed at that time by electromyograph,
were the set of tensions. Delay times were readily observed.
B. KINESTHETIC POSITIONS. Originally this stage was considered the
coordination(s) among muscle groups, particularly those in opposition
due to the geometry of structures of bones and joints. The initial
focus was on some higher order system operating by setting suitable
combinations of muscle tensions as needed. Later it was realized
that some additional perceptual variable(s) was needed to form a
higher order perceptual variable. Neural detectors of joint position
were suggested as suitable, together with general recognition of
various kinesthetic sensors. These might, even, include stretching of
the skin, and perhaps other sensitive organs.
The operation of these two combined systems was readily observed, and
distinguished, in terms of the sequence of events and the
corresponding delay times.
The perceptual variables included muscle tensions, joint position
detectors, and, possibly, skin stretch sensors.
C. VISUAL POSITIONS. This was considered a "target" situation,
where the target position was changed at the same time the signal was
given. This involved higher order systems that operate by setting
reference levels for Kinesthetic Positions. Such higher order
systems needed additional time to reset the levels for the lower
order systems. At that stage of the demonstration, the need for
additional perceptual variables was not stated -- they were "obvious"
to those present. In fact, the only additional source of information
available at this level consists of the visual perceptual
In this demonstration, the three systems involved are readily
observed, and they can be distinguished in terms of the sequence of
events and the corresponding delay times.
At this stage, the perceptual variables include all those in A and B
combining with visual variables to form perceptions of spatial
D. TRACKING. Up to this point all the demonstrations have been
limited to situations that are either static in time, or involve a
change from one static situation to another. Time relations have
been determined only by the internal characteristics of the subject's
Cases D1 - D5 includes the same spatial variables previously used,
but now adds temporal variables. E adds these variables to the
situation, presenting the movement(s) to be followed by S. S quickly
assembles the necessary lower order systems, and matches his own
temporal variables with those presented by E. The process of
assembling and adjusting these systems is demonstrated by the
irregularity and time delays observed.
Taken together, this group of demonstrations displays the previous
systems in terms of the temporal sequence of events and the related
Here the perceptual variables include all those in A, B and C
together with temporal perceptions. The combination results in the
formation of perceptions of controlled movements.
E. OTHER MUSCLE SYSTEMS. This demonstration repeated the previous
tracking activities, but included use of alternative sets of muscle
systems. The same lower order results were obtained, but now the
relation between E and S were modified: S was required to decide
whether to continue to use the same muscle systems or change to match
E's systems. For a small change (from E's right hand to his left
hand), S simply continued using the same hand, spatial variables, and
temporal variables. Had the instructions been somewhat different, S
might have not only tracked E's movements, but also followed his
selection of muscle systems. This could have been extended to
coordinated movements composing a simple dance.
As before, the same spatial and temporal variables are displayed,
with their delay times. However the interactions between E and S, as
individual hierarchical control systems is an added set of perceptual
F. LEADER-FOLLOWER. This demonstration still includes all the lower
order variables of the preceding procedures, but now makes the
relations between the "Leader" and the "Follower" explicit. In
addition, the inclusion of the "Caller," "C," enlarges the perceptual
variables of "Social Systems" (interpersonal interaction?) still a
This ends this "Discussion."
"Temporal Variables" will be posted later, to be followed by "Skills."
Regards, Bob Clark