significance of zero

[Bruce Nevin 2018-04-23_12:52:05 ET]

A propos of nothing, this might be useful to recall:

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself is largely random? The result of this view has been a drastic lowering of scientific standards.

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

Martin Taylor 2018.04.23.14.23]

[Bruce Nevin 2018-04-23_12:52:05 ET]

A propos of nothing, this might be useful to recall:

          the formal definition of a reference level: that level

of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p.
495)

Well, Bill may have said it, but according to the rest of his

theory, he mis-spoke. He knew that for a perception to equal its
reference level, the output quantity must be equal and opposite to
the disturbing quantity, and that usually is not zero. Perhaps what
he intended was “at which the output does not change unless the
disturbance changes”. This doesn’t affect the rest of the material
you quoted.

Martin
···
          The

reference level, like the output and disturbance, is an
empirical observation in the environment that the organism
and the investigator have in common.

        The corresponding reference signal, like the perceptual

signal and the error signal, is imaginary in that peculiar
sense that we call theory.

          Most physical scientists, of course (with recent

exceptions), think they are “discovering reality.” Let
them. Whatever they think they’re doing, they’re making
models in their imaginations. But they’re doing it in a
disciplined way that demands perfection. They would say
that nature is governed by exact and immutable laws, so
they’re simply trying to improve their analyses to make
them into closer and closer approximations to the actual
exact laws. It’s nature that is perfect, as it can be only
and exactly what it is. The effect is the same: the models
are worked over and reworked and tested with
ever-increasing finesse, any discrepancy between the
model’s behavior and what is observed being reason enough
to work on the model some more.

          In the behavioral sciences, the long centuries of

failure have resulted in a different view of natural laws:
organisms are inherently variable and inexact. What’s the
point in demanding perfection of models (or any method)
when nature itself is largely random? The result of this
view has been a drastic lowering of scientific standards.

(Bill to Phil 8/9/89, in * Dialogue concerning the two
chief approaches to a science of life* p. 450)

[From Bruce Abbott (2018.04.24.0840 EDT)]

Martin Taylor 2018.04.23.14.23]

[Bruce Nevin 2018-04-23_12:52:05 ET]

A propos of nothing, this might be useful to recall:

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

Well, Bill may have said it, but according to the rest of his theory, he mis-spoke. He knew that for a perception to equal its reference level, the output quantity must be equal and opposite to the disturbing quantity, and that usually is not zero. Perhaps what he intended was “at which the output does not change unless the disturbance changes”. This doesn’t affect the rest of the material you quoted.

Bill was correct to say that the reference level is� that level of input at which the output just becomes zero,� assuming that he was talking about the canonical proportional control system. When perception equals reference, error is zero and, therefore, output is zero. However, this state of affairs will occur in the steady state only when the disturbance is zero. When the disturbance is not zero, the system will develop a counteracting non-zero output, but to do so it must maintain some small error, the size of that error being inversely related to the system’s loop gain.

Even when a disturbance is present, the error, and thus the output, will become zero whenever the perception equals the reference level, as may happen transiently as the disturbance varies over time.

Bruce

Martin

···

The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself is largely random? The result of this view has been a drastic lowering of scientific standards.

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

[Bruce Nevin 2018-04-24_09:22:44]

Martin Taylor 2018.04.23.14.23–

Bruce Abbott (2018.04.24.0840 EDT)–

I agree with both of you, of course, but I understood disturbances to contribute to input.

···

On Tue, Apr 24, 2018 at 8:42 AM, Bruce Abbott bbabbott@frontier.com wrote:

[From Bruce Abbott (2018.04.24.0840 EDT)]

Â

Martin Taylor 2018.04.23.14.23]

[Bruce Nevin 2018-04-23_12:52:05 ET]

Â

A propos of nothing, this might be useful to recall:Â

Â

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

Well, Bill may have said it, but according to the rest of his theory, he mis-spoke. He knew that for a perception to equal its reference level, the output quantity must be equal and opposite to the disturbing quantity, and that usually is not zero. Perhaps what he intended was “at which the output does not change unless the disturbance changes”. This doesn’t affect the rest of the material you quoted.

Â

Bill was correct to say that the reference level is� that level of input at which the output just becomes zero,� assuming that he was talking about the canonical proportional control system. When perception equals reference, error is zero and, therefore, output is zero. However, this state of affairs will occur in the steady state only when the disturbance is zero. When the disturbance is not zero, the system will develop a counteracting non-zero output, but to do so it must maintain some small error, the size of that error being inversely related to the system’s loop gain.

Â

Even when a disturbance is present, the error, and thus the output, will become zero whenever the perception equals the reference level, as may happen transiently as the disturbance varies over time.

Â

Bruce

Martin

Â

The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Â

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

Â

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself is largely random? The result of this view has been a drastic lowering of scientific standards.

Â

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

Â

[From Bruce Abbott (2018.04.24.1245 EDT)]

[Bruce Nevin 2018-04-24_09:22:44]

Martin Taylor 2018.04.23.14.23–

Bruce Abbott (2018.04.24.0840 EDT)–

I agree with both of you, of course, but I understood disturbances to contribute to input.

They do. Disturbances cause the input to change, thus the perception. Some ambiguity may arise in that the term “disturbance� sometimes has referred to the causal agent itself and sometimes to the effect of that agent on the input, but either way, it is the input that the disturbance affects.

The disturbance may push the perception away from its reference value; the error thus generated produces an output of opposite sign that tends to push the perception toward the reference value. But the disturbance also may push the perception toward the reference value, reducing the error, in consequence of which the disturbance-opposing output is reduced.

Bruce

···

/B

On Tue, Apr 24, 2018 at 8:42 AM, Bruce Abbott bbabbott@frontier.com wrote:

[From Bruce Abbott (2018.04.24.0840 EDT)]

Martin Taylor 2018.04.23.14.23]

[Bruce Nevin 2018-04-23_12:52:05 ET]

A propos of nothing, this might be useful to recall:

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

Well, Bill may have said it, but according to the rest of his theory, he mis-spoke. He knew that for a perception to equal its reference level, the output quantity must be equal and opposite to the disturbing quantity, and that usually is not zero. Perhaps what he intended was “at which the output does not change unless the disturbance changes”. This doesn’t affect the rest of the material you quoted.

Bill was correct to say that the reference level is� that level of input at which the output just becomes zero,� assuming that he was talking about the canonical proportional control system. When perception equals reference, error is zero and, therefore, output is zero. However, this state of affairs will occur in the steady state only when the disturbance is zero. When the disturbance is not zero, the system will develop a counteracting non-zero output, but to do so it must maintain some small error, the size of that error being inversely related to the system’s loop gain.

Even when a disturbance is present, the error, and thus the output, will become zero whenever the perception equals the reference level, as may happen transiently as the disturbance varies over time.

Bruce

Martin

The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself is largely random? The result of this view has been a drastic lowering of scientific standards.

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

[Bruce Nevin 2018-04-24_17:14:00 ET]

Yes. The input is the effect of aspects of the environment on those sensors that are involved in the control loop. The input is affected both by disturbances and by the output(s) of those effectors that are involved in the control loop.Â

Phrasing it with such technical nicety makes ‘input’ a term of theory rather than an empirical quantity. What we may measure empirically is understood to be a good enough summation.

···

On Tue, Apr 24, 2018 at 12:47 PM, Bruce Abbott bbabbott@frontier.com wrote:

[From Bruce Abbott (2018.04.24.1245 EDT)]

Â

[Bruce Nevin 2018-04-24_09:22:44]

Â

Martin Taylor 2018.04.23.14.23–

Bruce Abbott (2018.04.24.0840 EDT)–

Â

I agree with both of you, of course, but I understood disturbances to contribute to input.

Â

They do. Disturbances cause the input to change, thus the perception. Some ambiguity may arise in that the term “disturbance� sometimes has referred to the causal agent itself and sometimes to the effect of that agent on the input, but either way, it is the input that the disturbance affects.

Â

The disturbance may push the perception away from its reference value; the error thus generated produces an output of opposite sign that tends to push the perception toward the reference value. But the disturbance also may push the perception toward the reference value, reducing the error, in consequence of which the disturbance-opposing output is reduced.

Â

Bruce

Â

/B

Â

On Tue, Apr 24, 2018 at 8:42 AM, Bruce Abbott bbabbott@frontier.com wrote:

[From Bruce Abbott (2018.04.24.0840 EDT)]

Â

Martin Taylor 2018.04.23.14.23]

[Bruce Nevin 2018-04-23_12:52:05 ET]

Â

A propos of nothing, this might be useful to recall:Â

Â

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

Well, Bill may have said it, but according to the rest of his theory, he mis-spoke. He knew that for a perception to equal its reference level, the output quantity must be equal and opposite to the disturbing quantity, and that usually is not zero. Perhaps what he intended was “at which the output does not change unless the disturbance changes”. This doesn’t affect the rest of the material you quoted.

Â

Bill was correct to say that the reference level is� that level of input at which the output just becomes zero,� assuming that he was talking about the canonical proportional control system. When perception equals reference, error is zero and, therefore, output is zero. However, this state of affairs will occur in the steady state only when the disturbance is zero. When the disturbance is not zero, the system will develop a counteracting non-zero output, but to do so it must maintain some small error, the size of that error being inversely related to the system’s loop gain.

Â

Even when a disturbance is present, the error, and thus the output, will become zero whenever the perception equals the reference level, as may happen transiently as the disturbance varies over time.

Â

Bruce

Martin

Â

The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Â

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

Â

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself is largely random? The result of this view has been a drastic lowering of scientific standards.

Â

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

Â

Â

Wrong !!!

image001144.png

···

From: Bruce Nevin bnhpct@gmail.com
Sent: Monday, April 23, 2018 7:00 PM
To: CSG csgnet@lists.illinois.edu
Subject: significance of zero

[Bruce Nevin 2018-04-23_12:52:05 ET]

A propos of nothing, this might be useful to recall:

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

BN : The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

HB : Where did you get this one ? You are generalizing wrong again. How many times do I have to tell you that there is no control outside. There is no reference state or level or whatever you imagine in the environmebt of organism.

Bill P :

cid:image001.png@01D3DC28.E9192C60

HB : Reference level for »essential variables« is far from being imagination as you are presenting »reference level« in environment. You understood Bill wrong, because of short description. See full description. It seems that you are seeking »poor« Bills explanations, so that you can serve your BNCT theory of »Control of behavior«. Like Rick is doing.

There is no reference level in environment. Reference level is inside organism not outside. Generally speaking in PCT. Everything what is concerning references is inside organisms. It’s important feature in medical examination of health state in body. Reference level for »essential variables« is quite well measured on a »scale of magnitudes« (physiological limits). And that’s what is keeping organisms alive.

There is no reference level »in common« in environment which can be »empirically observed« by organism and investigator. Organism has it’s reference level (inside) and investigator has his reference level (inside) which are different. And perception in both cases is matched to references inside both organisms. They maybe can imagine that some »reference« is outside. But there is no control outside. Of course you can imagine whatever you want. Even »empirical observation«. You are again confusing everbody arround with your BNCT »Control of behavior«. Because that it seems that you are getting at. When will you start to think in terms of »Perceptual control« ???

Boris

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself is largely random? The result of this view has been a drastic lowering of scientific standards.

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

[Eetu Pikkarainen 2018-04-25_09:07:20 UTC]

This is interesting discussion. First the concept of disturbance has all the time annoyed me because it can mean two different things:

It is (at least from an ordinary or layman point of view) an effect which pushes the control system out of balance changing the perception so that it will go out from reference.
So in the beginning there is something which causes a perception and if that perception is near enough to the reference value no output is needed. And then appears a disturbance which changes things and causes the error and requires output. So what is that
something which caused the original – in the reference zone stayiing – perception?

According to PCT vocabulary it is also disturbance, and it sounds strange even though I have tried to customize to it.
J

(My idea at the moment is that the disturbance could be divided in two according to the classical actant model of Greimas: helper and opponent.)

Secondly about that original quotation. Let’s have again the previous situation where I have a perception which is in reference zone and that requires no output. Say, there
is an object in the table in the place where I think it should be. Then appears a disturbance, say a strong wind (or electric magnetism or the table starts to lean) which starts to move the object to a wrong place. That requires my output and I start to push
the object back. If I push hard enough I will get the object back to its original place, but because the disturbance continues I cannot stop my pushing. I can keep the error in zero only by continuing the output. So it seems that Bill’s saying cannot hold
generally, as Martin already said. And when I read Bruce A’s comment more carefully it fits here too: but if I get the object exactly to its original place will there then remain that “small error�? Perhaps it is just that I am not a “canonical proportional
control system�? I think I have asked this before but do there physically exist those?

···

Eetu

  • Please, regard my statements as questions –
    no mattter how they are fomulated.

From: Bruce Abbott bbabbott@frontier.com
Sent: 24. huhtikuuta 2018 19:47
To: csgnet@lists.illinois.edu
Subject: RE: significance of zero

[From Bruce Abbott (2018.04.24.1245 EDT)]

[Bruce Nevin 2018-04-24_09:22:44]

Martin Taylor 2018.04.23.14.23–

Bruce Abbott (2018.04.24.0840 EDT)–

I agree with both of you, of course, but I understood disturbances to contribute to input.

They do. Disturbances cause the input to change, thus the perception. Some ambiguity may arise in that the term “disturbance� sometimes has referred to the causal agent itself and sometimes to the effect of that agent
on the input, but either way, it is the input that the disturbance affects.

The disturbance may push the perception away from its reference value; the error thus generated produces an output of opposite sign that tends to push the perception toward the reference value. But the disturbance also
may push the perception toward the reference value, reducing the error, in consequence of which the disturbance-opposing output is reduced.

Bruce

/B

On Tue, Apr 24, 2018 at 8:42 AM, Bruce Abbott bbabbott@frontier.com wrote:

[From Bruce Abbott (2018.04.24.0840 EDT)]

Martin Taylor 2018.04.23.14.23]

[Bruce Nevin 2018-04-23_12:52:05 ET]

A propos of nothing, this might be useful to recall:

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

Well, Bill may have said it, but according to the rest of his theory, he mis-spoke. He knew that for a perception to equal its reference level, the output quantity must be equal and opposite to the disturbing quantity, and that usually is not zero. Perhaps
what he intended was “at which the output does not change unless the disturbance changes”. This doesn’t affect the rest of the material you quoted.

Bill was correct to say that the reference level is� that level of input at which the output just becomes zero,� assuming that he was talking about the canonical proportional control system. When perception equals reference, error is zero
and, therefore, output is zero. However, this state of affairs will occur in the steady state only when the disturbance is zero. When the disturbance is not zero, the system will develop a counteracting non-zero output, but to do so it must maintain some
small error, the size of that error being inversely related to the system’s loop gain.

Even when a disturbance is present, the error, and thus the output, will become zero whenever the perception equals the reference level, as may happen transiently as the disturbance varies over time.

Bruce

Martin

The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands
perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and
exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself
is largely random? The result of this view has been a drastic lowering of scientific standards.

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

[From Bruce Abbott (2018.04.25.0955 EST)]

[Eetu Pikkarainen 2018-04-25_09:07:20 UTC]

This is interesting discussion. First the concept of disturbance has all the time annoyed me because it can mean two different things:

It is (at least from an ordinary or layman point of view) an effect which pushes the control system out of balance changing the perception so that it will go out from reference. So in the beginning there is something which causes a perception and if that perception is near enough to the reference value no output is needed. And then appears a disturbance which changes things and causes the error and requires output. So what is that something which caused the original – in the reference zone staying – perception?

(My idea at the moment is that the disturbance could be divided in two according to the classical actant model of Greimas: helper and opponent.)

Borrowing from sensory physiology,  one wants to distinguish is between the “distalâ€? and “proximalâ€? disturbance. The distal disturbance is the source, e.g., the wind. The distal disturbance acts on qi, its effect on qi (e.g., the push of the wind against your car) being determined by the laws of physics (the function relating cause to effect). This effect (the push on the car that affects qi) is the proximal disturbance.Â

To my knowledge, the terms “distal� and “proximal� have not been used in PCT to make this distinction; usually one understands what the term “disturbance� refers to from the context.  Our system diagrams often leave out the environmental function that mediates between cause and effect, leaving only an arrow labeled “disturbance� that inputs to qi (along with the output of the environmental feedback function).

Secondly about that original quotation. Let’s have again the previous situation where I have a perception which is in reference zone and that requires no output. Say, there is an object in the table in the place where I think it should be. Then appears a disturbance, say a strong wind (or electric magnetism or the table starts to lean) which starts to move the object to a wrong place. That requires my output and I start to push the object back. If I push hard enough I will get the object back to its original place, but because the disturbance continues I cannot stop my pushing. I can keep the error in zero only by continuing the output. So it seems that Bill’s saying cannot hold generally, as Martin already said. And when I read Bruce A’s comment more carefully it fits here too: but if I get the object exactly to its original place will there then remain that “small error�? Perhaps it is just that I am not a “canonical proportional control system�? I think I have asked this before but do there physically exist those?

The �small error� remains only if the control system is a proportional one, so that the output must be proportional to the magnitude of the error. So if there is a disturbance acting on qi, the system can oppose that disturbance only by failing to entirely eliminate the error.

However, an “integral� control system can produce an output in the absence of error. In the integral system, the error at any given moment is the integral (sum) of all previous error levels. If the perception is below the reference, a positive error will appear that drives the perception toward the reference. This error will summate over time, but the rate of increase will be slowing as the perception approaches the reference value. When the two are equal, there will be zero difference but the cumulated error will still be large, so the output will continue and the perception will rise above the reference value. Now the sign of the difference has reversed, so the current difference will subtract from the current integral error. Eventually the integral error will become zero and the system will stabilize at the reference value.

This is true even if there is a constant disturbance acting on qi. The integral error will be zero when the rate of change in qi caused by the disturbance is equaled by the rate of change in qi caused by the output. So with integral error at zero (perception matching reference), the output can be non-zero.

Bruce

Eetu

  • Please, regard my statements as questions –
    no matter how they are fomulated.
···

From: Bruce Abbott bbabbott@frontier.com
Sent: 24. huhtikuuta 2018 19:47
To: csgnet@lists.illinois.edu
Subject: RE: significance of zero

[From Bruce Abbott (2018.04.24.1245 EDT)]

[Bruce Nevin 2018-04-24_09:22:44]

Martin Taylor 2018.04.23.14.23–

Bruce Abbott (2018.04.24.0840 EDT)–

I agree with both of you, of course, but I understood disturbances to contribute to input.

They do. Disturbances cause the input to change, thus the perception. Some ambiguity may arise in that the term “disturbance� sometimes has referred to the causal agent itself and sometimes to the effect of that agent on the input, but either way, it is the input that the disturbance affects.

The disturbance may push the perception away from its reference value; the error thus generated produces an output of opposite sign that tends to push the perception toward the reference value. But the disturbance also may push the perception toward the reference value, reducing the error, in consequence of which the disturbance-opposing output is reduced.

Bruce

/B

On Tue, Apr 24, 2018 at 8:42 AM, Bruce Abbott bbabbott@frontier.com wrote:

[From Bruce Abbott (2018.04.24.0840 EDT)]

Martin Taylor 2018.04.23.14.23]

[Bruce Nevin 2018-04-23_12:52:05 ET]

A propos of nothing, this might be useful to recall:

the formal definition of a reference level: that level of input at which the output just becomes zero.

(Bill Powers (941024.0945 MDT) = Bill to Phil Runkel, Dialogue p. 495)

Well, Bill may have said it, but according to the rest of his theory, he mis-spoke. He knew that for a perception to equal its reference level, the output quantity must be equal and opposite to the disturbing quantity, and that usually is not zero. Perhaps what he intended was “at which the output does not change unless the disturbance changes”. This doesn’t affect the rest of the material you quoted.

Bill was correct to say that the reference level is� that level of input at which the output just becomes zero,� assuming that he was talking about the canonical proportional control system. When perception equals reference, error is zero and, therefore, output is zero. However, this state of affairs will occur in the steady state only when the disturbance is zero. When the disturbance is not zero, the system will develop a counteracting non-zero output, but to do so it must maintain some small error, the size of that error being inversely related to the system’s loop gain.

Even when a disturbance is present, the error, and thus the output, will become zero whenever the perception equals the reference level, as may happen transiently as the disturbance varies over time.

Bruce

Martin

The reference level, like the output and disturbance, is an empirical observation in the environment that the organism and the investigator have in common.

The corresponding reference signal, like the perceptual signal and the error signal, is imaginary in that peculiar sense that we call theory.

Most physical scientists, of course (with recent exceptions), think they are “discovering reality.” Let them. Whatever they think they’re doing, they’re making models in their imaginations. But they’re doing it in a disciplined way that demands perfection. They would say that nature is governed by exact and immutable laws, so they’re simply trying to improve their analyses to make them into closer and closer approximations to the actual exact laws. It’s nature that is perfect, as it can be only and exactly what it is. The effect is the same: the models are worked over and reworked and tested with ever-increasing finesse, any discrepancy between the model’s behavior and what is observed being reason enough to work on the model some more.

In the behavioral sciences, the long centuries of failure have resulted in a different view of natural laws: organisms are inherently variable and inexact. What’s the point in demanding perfection of models (or any method) when nature itself is largely random? The result of this view has been a drastic lowering of scientific standards.

(Bill to Phil 8/9/89, in Dialogue concerning the two chief approaches to a science of life p. 450)

According to PCT vocabulary it is also disturbance, and it sounds strange even though I have tried to customize to it. J

[From Bruce Abbott (2018.04.25.0955 EST)]

Â

        [Eetu Pikkarainen 2018-04-25_09:07:20

UTC]

Â

        This is interesting discussion. First

the concept of disturbance has all the time annoyed me
because it can mean two different things:

        It is (at least from an ordinary or

layman point of view) an effect which pushes the control
system out of balance changing the perception so that it
will go out from reference. So in the beginning there is
something which causes a perception and if that perception
is near enough to the reference value no output is needed.
And then appears a disturbance which changes things and
causes the error and requires output. So what is that
something which caused the original – in the reference zone
staying – perception?

        According to PCT vocabulary it is also

disturbance, and it sounds strange even though I have tried
to customize to it. J

Â

        (My idea at the moment is that the

disturbance could be divided in two according to the
classical actant model of Greimas: helper and opponent.)

Â

      Borrowing from sensory physiology, Â one

wants to distinguish is between the “distal� and “proximal�
disturbance. The distal disturbance is the source, e.g., the
wind. The distal disturbance acts on qi, its effect on qi
(e.g., the push of the wind against your car) being determined
by the laws of physics (the function relating cause to
effect). This effect (the push on the car that affects qi) is
the proximal disturbance.Â

Â

      To my knowledge, the terms “distal� and

“proximal� have not been used in PCT to make this distinction;
usually one understands what the term “disturbance� refers to
from the context. Â Our system diagrams often leave out the
environmental function that mediates between cause and effect,
leaving only an arrow labeled “disturbance� that inputs to qi
(along with the output of the environmental feedback
function).

···

Eetu
- Please, regard my statements as questions –

          Â Â no matter how they are fomulated.

Â

From:
Bruce Abbott bbabbott@frontier.com
Sent: 24. huhtikuuta 2018 19:47
To: csgnet@lists.illinois.edu
Subject: RE: significance of zero

Â

        [From Bruce

Abbott (2018.04.24.1245 EDT)]

Â

          [Bruce Nevin

2018-04-24_09:22:44]

Â

              Martin Taylor

2018.04.23.14.23–

              Bruce Abbott

(2018.04.24.0840 EDT)–

Â

              I agree

with both of you, of course, but I understood
disturbances to contribute to input.

Â

              They do. 

Disturbances cause the input to change, thus the
perception. Some ambiguity may arise in that the term
“disturbance� sometimes has referred to the causal
agent itself and sometimes to the effect of that agent
on the input, but either way, it is the input that the
disturbance affects.

Â

              The

disturbance may push the perception away from its
reference value; the error thus generated produces an
output of opposite sign that tends to push the
perception toward the reference value. But the
disturbance also may push the perception toward the
reference value, reducing the error, in consequence of
which the disturbance-opposing output is reduced.

Â

Bruce

Â

/B

Â

            On Tue, Apr

24, 2018 at 8:42 AM, Bruce Abbott <bbabbott@frontier.com >
wrote:

                  [From

Bruce Abbott (2018.04.24.0840 EDT)]

Â

                  Martin Taylor

2018.04.23.14.23]

                        [Bruce

Nevin 2018-04-23_12:52:05 ET]

Â

                      A

propos of nothing, this might be useful to
recall:Â

Â

                            the

formal definition of a reference level:
that level of input at which the output
just becomes zero.

                          (Bill

Powers (941024.0945 MDT) = Bill to Phil
Runkel, Dialogue p. 495)

                  Well, Bill may have said it, but according to the

rest of his theory, he mis-spoke. He knew that for
a perception to equal its reference level, the
output quantity must be equal and opposite to the
disturbing quantity, and that usually is not zero.
Perhaps what he intended was “at which the output
does not change unless the disturbance changes”.
This doesn’t affect the rest of the material you
quoted.

Â

                  Bill

was correct to say that the reference level is�
that level of input at which the output just
becomes zero,� assuming that he was talking about
the canonical proportional control system. When
perception equals reference, error is zero and,
therefore, output is zero. However, this state of
affairs will occur in the steady state only when
the disturbance is zero. When the disturbance is
not zero, the system will develop a counteracting
non-zero output, but to do so it must maintain
some small error, the size of that error being
inversely related to the system’s loop gain.

Â

                  Even

when a disturbance is present, the error, and thus
the output, will become zero whenever the
perception equals the reference level, as may
happen transiently as the disturbance varies over
time.

Â

Bruce

                  Martin

Â

                            The

reference level, like the output and
disturbance, is an empirical observation
in the environment that the organism and
the investigator have in common.

                          The corresponding reference signal, like

the perceptual signal and the error
signal, is imaginary in that peculiar
sense that we call theory.

Â

                            Most

physical scientists, of course (with
recent exceptions), think they are
“discovering reality.” Let them.
Whatever they think they’re doing,
they’re making models in their
imaginations. But they’re doing it in a
disciplined way that demands perfection.
They would say that nature is governed
by exact and immutable laws, so they’re
simply trying to improve their analyses
to make them into closer and closer
approximations to the actual exact laws.
It’s nature that is perfect, as it can
be only and exactly what it is. The
effect is the same: the models are
worked over and reworked and tested with
ever-increasing finesse, any discrepancy
between the model’s behavior and what is
observed being reason enough to work on
the model some more.

Â

                            In

the behavioral sciences, the long
centuries of failure have resulted in a
different view of natural laws:
organisms are inherently variable and
inexact. What’s the point in demanding
perfection of models (or any method)
when nature itself is largely random?
The result of this view has been a
drastic lowering of scientific
standards.

Â

                          (Bill

to Phil 8/9/89, in * Dialogue concerning
the two chief approaches to a science of
life*Â p. 450)

Â

Â