[From Bill Powers (2009.04.27.0716 MDT)]
Richard Kennaway (2009.04.26.2216 BST) --
RK:====
Alien Space Bats have abducted you. You find yourself in a sealed cell, featureless but for two devices on the wall. One seems to be some sort of meter with an unbreakable cover, the needle of which wanders over a scale marked off in units, but without any indication of what, if anything, it is measuring. There is a red blob at one point on the scale. The other device is a knob next to the meter, that you can turn. The Alien Space Bats give you to know that you must ensure that the needle always remains close to the red dot. If you twiddle the knob at random, it seems to have some effect on the needle, but there is no fixed relationship. You do not know what moves the needle, and you do not know what turning the knob actually does. You know nothing of what lies outside the cell. You just have the needle, the red dot, and the knob. To make matters worse, the red dot also moves along the scale from time to time, and nothing you do seems to have any effect on it. You don't know why, only that wherever it moves, you must keep the needle aligned with it.
Solve this problem.
What a great idea! I can't wait to see the reaction you get to this. According to Modern Control theory, this is an impossible task, because you can't even do a "system identification." You totally lack a model of the plant. You don't even know if there IS a plant behind the wall. Those things on the wall ARE the plant.
May I suggest that the Alien Space Bats have simply arranged matters so if you keep the needle close to the red blob, you prevent some bad feelings that get worse as the needle gets farther from the blob. They don't even tell you that: you have to find it out for yourself. They induce the feelings by electromagnetic induction; you can't tell where they're coming from.
This is also a great way to show how the world looks from one level in the hierarchy; instead of "bad feelings" you just want the needle to behave in some particular way, for no reason.
I'll save this with the others in this thread
Best,
Bill P.
ยทยทยท
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This is for an audience accustomed to thinking in terms of Bayesian reasoning, utility functions, prediction, optimisation, and so on, in the context of human rationality, i.e. how to think better. I then go on to say that this is what such mundane devices as a room thermostat or the cruise control on a car do, pointing out that they successfully push back on all the disturbing forces, despite having no idea that such forces exist, making no predictions, using no models, performing no Bayesian calculations, etc. Eventually I will say that that scenario is the situation that all living organisms are in, perhaps with many meters and knobs, but still shut in the cell with no possibility of digging one's way out to get any more "direct" contact with reality. At most you just get a bigger cell with more knobs and meters. And while the theorems of Bayesian probability are correct, successful control does not require any of that apparatus.
Then I intend to cover hierarchical arrangements of control systems, conflict, and so forth, and giving pointers to the PCT demos.
I hope I can do your work justice.
--
Richard Kennaway, jrk@cmp.uea.ac.uk, Richard Kennaway
School of Computing Sciences,
University of East Anglia, Norwich NR4 7TJ, U.K.No virus found in this incoming message.
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