Transcript of CYBERNETICS Dr. Tom Froese. The nature of “equilibrium” “We have three objects on the table...
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- CYBERNETICS Dr. Tom Froese
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- The nature of equilibrium We have three objects on the table
before us: one is a cube resting on one face, the second is a
sphere, and the third is an inverted cone exactly balanced on its
point. They correspond to the usual stable, neutral and unstable
equilibria respectively. The criterion used to distinguish the
types of equilibria is that we apply a small disturbance to the
object and see what happens. Asbhy (1940, p. 479)
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- Three kinds of equilibria
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- Stable equilibrium We may now define stable equilibrium more
precisely: a variable is in stable equilibrium if, when it is
disturbed, reactive forces are setup which act back on the variable
so as to oppose the initial disturbance. (Ashby 1940, p. 479)
Stable attractor
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- Three kinds of equilibria
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- Necessary for existence Finally, there is one point of
fundamental importance which must be grasped. It is that stable
equilibrium is necessary for existence, and that systems in
unstable equilibrium inevitably destroy themselves. Consequently,
if we find that a system persists, in spite of the usual small
disturbances which affect every physical body, then we may draw the
conclusion with absolute certainty that the system must be in
stable equilibrium. Ashby (1940, p. 482)
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- Stable equilibrium = adaptedness It is suggested here that
adaptive behaviour may be identical with the behaviour of a system
in stable equilibrium, and that this latter concept may, with
advantage, be substituted for the former. The advantages of this
latter concept are that (1) it is purely objective, (2) it avoids
all metaphysical complications of purpose, (3) it is precise in its
definition, and (4) it lends itself immediately to quantitative
studies. (Ashby 1940, p. 483) Beer (1997) Domain of viability
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- Definition of cybernetics According to Norbert Wiener (1948),
cybernetics was born in the confluence of three lines of work: 1.
Information theory 2. Neural networks 3. Connections between
negative feedback and purposive behavior The first two were closely
related, for example in the work of McCulloch and Pitts (1943): a
logical calculus of the ideas immanent in nervous activity.
Firing/no-firing = on/off = 1/0
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- Types of feedback Differences in stability?
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- Negative feedback --
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- Negative feedback control Centrifugal governor
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- Negative feedback and teleology
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- although a gun may be used for a definite purpose, the
attainment of a goal is not intrinsic to the performance of the
gun; random shooting can be made, deliberately purposeless. Some
machines, on the other hand, are intrinsically purposeful. A
torpedo with a target-seeking mechanism is an example. All
purposeful behavior may be considered to require negative
feed-back. (Rosenblueth, Wiener and Bigelow 1943, p. 19)
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- Categories of behavior Rosenblueth, Wiener and Bigelow
(1943)
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- Arturo Rosenblueth Rosenblueth was born in 1900 in Ciudad
Guerrero, Chihuahua. He began his studies in Mexico City, then
traveled to Berlin and Paris where he obtained his medical degree.
Returning to Mexico city in 1927, he engaged in teaching and
research in physiology. In 1930 he obtained a Guggenheim
Scholarship and moved to Harvard University, to the department of
Physiology, then directed by Walter Cannon. With Cannon he explored
the chemical mediation of homeostasis. Rosenblueth co-wrote
research papers with both Cannon and Norbert Wiener, pioneer of
cybernetics. Rosenblueth was an influential member of the core
group at the Macy Conferences. In 1944 Rosenblueth became professor
of physiology at the National Autonomous University of Mexico and,
in 1961, director of the Center for Scientific Research and
Advanced Studies (Cinvestav) at the National Polytechnic Institute.
Arturo Rosenblueth died September 20, 1970 in Mexico City.
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- Grey Walters tortoises
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- From feedback to complexity The concept of 'feedback', so
simple and natural in certain elementary cases, becomes artificial
and of little use when the interconnections between the parts
become more complex [...]. Such complex systems cannot be treated
as an interlaced set of more or less independent feedback circuits,
but only as a whole. For understanding the general principles of
dynamic systems, therefore, the concept of feedback is inadequate
in itself. What is important is that complex systems, richly cross-
connected internally, have complex behaviors, and that these
behaviors can be goal-seeking in complex patterns. Ashby (1957, p.
54)
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- Science and consciousness Throughout the book, consciousness
and its related subjective elements are not used for the simple
reason that at no point have I found their introduction necessary.
This is not surprising, for the book deals with only one of the
properties of the brain Such an observation, showing that
consciousness is sometimes not necessary, gives us no right to
deduce that consciousness does not exist. The truth is quite
otherwise, for the fact of the existence of consciousness is prior
to all other facts. Ashby (1960, p. 11)
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- Adaptation v2.0 Ashby dedicates his first book, Design for a
Brain, to systematically answering the question: why does the burnt
kitten avoid the fire?
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- The Homeostat
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- Why does the burnt kitten avoid the fire?
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- The Ultrastable System The arrows to and from R represent, of
course, the sensory and motor channels. The part R belongs to the
organism, []. R is defined as the system that acts when the kitten
reacts to the fire the part responsible for the overt behaviour.
Ashby (1960, p. 80)
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- The Ultrastable System the kitten has a variety of possible
reactions, some wrong, some right. This variety of reactions
implies [] that some parameters, call them S, have a variety of
values their primary action is to affect the kittens behavior Ashby
(1960, p. 80)
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- The Ultrastable System The essential variables must now be
introduced The essential variables have been represented
collectively by a dial with a pointer, and with two limit-marks, to
emphasize that what matters about the essential variables is
whether or not the value is within physiological limits. Ashby
(1960, p. 81)
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- The Ultrastable System In the case we are considering, the
reacting part R is not specially related or adjusted to what is in
the environment and how it is joined to the essential variables.
Thus the reacting part R can be though of as an organism trying to
control the output of a Black Box (the environment), the contents
of which is unknown to it. Ashby (1960, p. 82)
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- The Ultrastable System the essential variables are to have an
effect on which behavior the kitten will produce; and this is
equivalent to saying that in the diagram of immediate effects there
must be a channel from the essential variables to the parameters
The organism that can adapt thus has a motor output to the
environment and two feedback loops Ashby (1960, p. 82)
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- Distinct paradigms of cybernetics Rosenblueth et al. (1943)
Single feedback loop Guided adaptation Environmental state is
internally represented Appropriate response is internally computed
Symbolic AI Ashby (1960) Double feedback loop Random adaptation
Environmental state is internally unknown Appropriate response is
interactively emergent Embodied AI
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- Adaptation to inverting goggles Erismann 1930s Kohler 1950s and
60s Demonstrated the plasticity of perceptual systems.
Technologically inverted senses would part by part adapt over time
and return to normal. Which paradigm can explain this better?
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- Significance of the homeostat I cant actually think of any
prior example of a real machine that would randomly open-endedly,
as I would say reconfigure itself in response to its inputs. It
seems reasonable, then, to speak of the homeostat as having a kind
of agency it did things in the world that sprang, as it were, from
inside itself, rather than having to be fully specified from
outside in advance. Pickering (2002, p. 417) But is the homeostat
really capable of open-ended self- transformation? Can the
principle of ultrastability do any real work?
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- Gordon Pask
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- Stafford Beer
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- Homeostasis in mobile robots Di Paolo (2003)
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- Homeostasis in robots Di Paolo (2003)
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- The collapse of cybernetics Shannon, C. E. (1948), A
Mathematical Theory of Communication Information theory is the
study of the encoding, decoding, storage and transmission of
information.
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- Entropy as information
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- The rise of computer science
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- History of cognitive science Froese (2010)
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- History of alternative paradigms
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- Homework Please read the whole article if possible: Di Paolo,
E. A. (2010). Robotics inspired in the organism. Intellectica,
1-2(53-54): 129162. Optional: Rosenblueth, A., Wiener, N. &
Bigelow, J. (1943). Behavior, purpose and teleology. Philosophy of
Science, 10(1): 18-24