RichardKennaway comments on Behavior: The Control of Perception - Less Wrong

30 Post author: Vaniver 21 January 2015 01:21AM

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Comment author: Vaniver 21 January 2015 04:26:38PM *  4 points [-]

Seems I should be looking for a function of the inputs that is "surprisingly" approximately constant

I think in most situations where you don't have internal observations of the various actors, it's more likely that outputs will be constant than a function of the inputs. That is, a control system adjusts the relationship between an input and an output, often by counteracting it completely--thus we would see the absence of a relationship that we would normally expect to see. (But if we don't know what we would normally expect, then we have trouble.)

Anyone have a link to a good paper on this?

I'm leaning pretty heavily on a single professor/concept for this answer, but there's a phrase called "Milton Friedman's Thermostat," perhaps best explained here (which also has a few links for going further down the trail):

If a house has a good thermostat, we should observe a strong negative correlation between the amount of oil burned in the furnace (M), and the outside temperature (V). But we should observe no correlation between the amount of oil burned in the furnace (M) and the inside temperature (P). And we should observe no correlation between the outside temperature (V) and the inside temperature (P).

An econometrician, observing the data, concludes that the amount of oil burned had no effect on the inside temperature. Neither did the outside temperature. The only effect of burning oil seemed to be that it reduced the outside temperature. An increase in M will cause a decline in V, and have no effect on P.

A second econometrician, observing the same data, concludes that causality runs in the opposite direction. The only effect of an increase in outside temperature is to reduce the amount of oil burned. An increase in V will cause a decline in M, and have no effect on P.

But both agree that M and V are irrelevant for P. They switch off the furnace, and stop wasting their money on oil.

They also give another example with a driver adjusting how much to press the gas pedal based on hills here, along with a few ideas on how to discover the underlying relationships.

I feel like it's worth mentioning the general project of discovering causality (my review of Pearl, Eliezer's treatment), but that seems like it's going in the reverse direction. If a controller is deleting correlations from your sense data, that makes discovering causality harder, and it seems difficult to say "aha, causality is harder to discover than normal, therefore there are controllers!", but that might actually be effective.

Comment author: RichardKennaway 22 January 2015 12:11:19AM *  1 point [-]

That is, a control system adjusts the relationship between an input and an output, often by counteracting it completely--thus we would see the absence of a relationship that we would normally expect to see.

The words "input" and "output" are not right here. A controller has two signals coming into it and one coming out of it. What you above called the "output" is actually one of the input signals, the perception. This is fundamental to understanding control systems.

The two signals going into the controller are the reference and the perception. The reference is the value at which the control system is trying to bring the perception to. The signal coming out of the controller is the output, action or behaviour of the controller. The action is being emitted in order to bring the perception towards the reference. The controller is controlling the relationship between its two input signals, trying to make that relationship the identity. The italicised words are somewhere between definitions and descriptions. They are the usual words used to name these signals in PCT, but this usage is an instance of their everyday meanings.

In concrete terms, a thermostat's perception is (some measure of) the actual temperature. Its reference signal is the setting of the desired temperature on a dial. Its output or behaviour is the signal it sends to turn the heat source on and off. In a well-functioning control system, one observes that as the reference changes, the perception tracks it very closely, while the output signal has zero correlation with both of them. The purpose of the behaviour is to control the perception -- hence the title of William Powers' book, "Behavior: The Control of Perception". All of the behaviour of living organisms is undertaken for a purpose: to bring some perception close to some reference.

Comment author: Vaniver 22 January 2015 12:52:34AM *  1 point [-]

The words "input" and "output" are not right here.

Yeah, that paragraph was sloppy and the previous sentence didn't add much, so I deleted it and reworded the sentence you quoted. I'm used to flipping my perspective around a system, and thus 'output' and 'input' are more like 'left' and 'right' to me than invariant relationships like 'clockwise' and 'counterclockwise'-- with the result that I'll sometimes be looking at something from the opposite direction of someone else. "Left! No, house left!"

(In this particular case, the system output and the controller input are the same thing, and the system input is the disturbance that the controller counteracts, and I assumed you didn't have access to the controller's other input, the reference.)

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