[From Bill Powers (2009.12.26.0735 MST)]
Finally got on standard time. No wonder I'm so sleepy!
It may be recalled that some time ago, while having a very similar discussion of the word control, I tried giving up and defining something called the "X Phenomenon." I am going to try something similar with the term "feedback control". I am going to invent (and perhaps patent or otherwise seek legal protection for) a new term, "cybernation" and all the usual grammatical forms such as cybernate, cybernating, cybernated, and so on. Cybernate is a transitive verb.
To cybernate means to act on the object to be cybernated in such a way as to bring at least one attribute or measure of the object to a predetermined state, static or dynamic, and maintain it in that state. Cybernating action is produced on the basis of knowledge about the currently sensed state of the object, without knowledge of any variable independent of the cybernator that affects that state at the same time it is being cybernated.
A cybernator senses the state of the object as the value of some function of the external attributes or measures (one or more) to be cybernated. The value is represented inside the cybernator as a perceptual signal; electrical, neural, hydraulic, or any other kind.
The value of the perceptual signal is compared with a reference signal by subtraction.
The resulting error signal enters an output function, and generates a physical effect on the attribute or measure of the object being cybernated. This effect is added to the effects of all independent variables acting on the same attribute or measure. The result is to bring the attribute or measure of the object being sensed to a predetermined state, static or dynamic, and to maintain it in that state, which is specified by the reference signal.
A hierarchy of cybernation consists of a number of cybernation systems at multiple levels, each level but the lowest operating by altering the reference signals in a subset of lower systems, and perceiving by applying computing functions to copies of the perceptual signals from lower levels, some but not all of which are cybernated.
In addition, this theory proposes a reorganizing system which alters parameters in the cybernation system on the basis of increases and decreases in the average values of error signals alone. It does not need any information about the physical nature of the object being cybernated or about any independent influences on the object.
I claim that using only this model of cybernation, we can account for all behaviors of living systems including those that have previously been explained using terms like feedback and feedforward. Perceptual Cybernation Theory, or PCT, is thus the more general theory, including both of the previous ones in a single explanatory system.
I don't expect this proposition to be greeted with any more enthusiasm than the X Phenomenon was, but at least the introduction of a new term forestalls free-associating on the word forms to bring other theories into this one. Some may suspect that cybernation bears suspiciously close resemblances to its predecessor that was expressed in terms like feedback and control, and a few of those may even think it is identical to its ancestor -- except that there is no provision in it for the added notion of feedforward. Yet cybernation theory can explain everything that feedforward theory was used to explain.
Try it; you'll see.