[From Rick Marken (2016.10.02.1940)]
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Fred Nickols (2016.10.02.1321 ET)
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RM: âqi corresponds to whatever variable aspect of the environment the system is controlling. It would correspond to the amount of coffee in the cup if this were the system controlling for the amount of coffee in the cup.â?
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FN: I know that what youâve written is essentially Billâs definition of âcontrolled quantityâ? but how does the system controlling some variable aspect of the environment square with the control of perception? Do we control perception, some aspect of the environment, or both?
RM: Again, it might help to think of it in terms of a thermostat. The aspect of the environment controlled by a thermostat is molecular motion at the sensor (the bimetallic strip); the thermostat perceives, via its sensor, this variable as an electrical current. When the thermostat maintains the electrical current (perception) at a reference (the temperature set point) it is controlling the molecular motion at the sensor, keeping it in a reference state.Â
RM: I think what may be hanging people up here is the fact that in PCT perceptual variables are assumed to be neural currents, analogous to the electrical current in the thermostat. But in PCT these neural currents can correspond to simple or complex perceptions. So whether the perceptual variable being controlled is your proximity to another person or the honesty of your discussions with that person, it is represented as the magnitude of a perceptual signal. Why we experience a neural current as distance in one case and degree of honesty in the other is a mystery. But according to PCT the reason why identical neural currents can represent different experiences (distance in one case and the other degree of honesty in the other) is because of the difference between the perceptual functions and inputs to those functions that produce those neural currents.Â
RM: This view of the nature of perception is consistent with the Nobel Prize winning research of Hubel and Weisel (Hubel DH and Wiesel TN. Receptive fields of single neurones in the cat’s striate cortex. J Physiol, 1959, 148: 574-591  http://jp.physoc.org/content/148/3/574.full.pdf+html). Their basic finding was that different neurons in the visual cortex respond differentialy to different patterns of light falling on particular areas (receptive fields) of the retina. Some neurons fire at a high rate when a vertical line is projected on a particular area of the retina and at a low rate when a horizontal line is projected on the same area. The area of the retina that a neuron is “looking at” is called a receptive field, which is a neural network that acts like a perceptual function in PCT. Hubel and Weisel viewed the  neurons attached to different receptive fields as “feature detectors”; some neurons detect vertical lines, some horizontal lines, etc. In PCT we would view these neurons as carrying a perceptual signal indicating, say, the orientation ofthe line.
RM: But the PCT model of perception is very much analogous to the receptive field discovery of Hubel and Weisel. The perceptual signal in PCT is an analog of some variable aspect of the environment, like the orientation of a line. Which aspect of the environment is represented by the perceptual signal is defined by the computations performed by the perceptual functoin (analogous to the receptive field).Â
RM: So according to PCT what you are experiencing as the world “out there” is just neural currents that are the outputs of different perceptual functions. Again, why it looks the way it does – why it looks to me like there is a computer on a table and some pictures on the wall and so on – is a mystery. But what you are controlling when you control, say, the temperature of the water in the shower is a neural current that is the output of a perceptual function (receptive field) that converts an aspect of the environment (rate of molecular movement at the skin) into that neural current. This is equivalent what a thermostat does when it controls temperature; it controls an electrical current that is the output of a perceptual function (the bimetallic strip) that converts an aspect of the environment (rate of molecular movement at the strip) into an electrical current. Whether the thermostat experiences that electrical current as temperature in the same way we experience neural currents as temperature is unknown.Â
RM: Anyway, if you lasted through this you will see that, from a PCT perspective, the perceptual signal is a neural current that is an analog of variations in simple or very complex aspects of the environment. And the “environment” is not what you see as being “out there” – that’s just neural signals that are the outputs of perceptual functions. The environment is known to us only as our best models of physics and chemistry. So it’s really not accurate to say that we control “environmental variables”; we control functions (or aspects) of environmental variables. Those functions are perceptual functions – so when we control perceptual variables (neural currents that are the outputs of perceptual functions) we are controlling functions (aspects) of the environment.
RM: The fact that we control perceptual functions (aspects) of environmental variables and not environmental variables themselves is the reason why Powers referred to the environmental correlate of the controlled perceptual variable the “controlled quantity” and not the “controlled environmental variable”.Â
RM: Hope this helps. Perception is a complicated topic so feel free to ask more questions about it if you want. Perception may be the most difficult (and least understood) aspect of Perceptual Control Theory.Â
BestÂ
Rick
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Fred (confused) Nickols
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From: Richard Marken [mailto:rsmarken@gmail.com]
Sent: Sunday, October 02, 2016 12:12 PM
To: csgnet@lists.illinois.edu
Subject: Re: [Attachment Removed] Some Simple Questions
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[From Rick Marken (2016.10.02.0910)]
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 Fred Nickols (2016.10.02.0826 ET)
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FN: The diagram below is essentially the same one that appears on page 286 in B:CP (2nd Edition). The only changes I have made were to remove the annotations Bill used for linear analysis purposes. I have a few simple questions:
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Is qo the controlled quantity?
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RM: No, qi is the controlled quantity.Â
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FN: Â Is p the perceptual signal that corresponds to qo?
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RM: No, p is the perceptual signal that corresponds to qi.
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 FN: In terms of my coffee cup example, is qo the amount of coffee in the cup?
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RM: qo is the output variable. Â qi corresponds to whatever variable aspect of the environment the system is controlling. It would correspond to the amount of coffee in the cup if this were the system controlling for the amount of coffee in the cup.Â
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FN: Â In terms of my coffee cup example, is p my perception of the amount of coffee in the cup?
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 RM: If that’s what this system is controlling then, yes. The perceptual signal in a control loop corresponds to whatever variable aspect of the environment the system is controlling. Think of it in terms of a thermostat. qi is the aspect of the environment that is sensed and controlled. So in the thermostat qi is a measure of molecular motion; this measure is converted into an electrical current, equivalent to the perceptual signal, p. So variations in p in a thermostat correspond to the rate of molecular motion at the thermostat’s sensor (the bimetallic coil). If instead of a thermostat the device is a humidity controller then qi is some measure of the ratio of molecular motion to vapor content of the air. And variations in p correspond to variations in this ratio.Â
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Rick
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Regards,
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Fred Nickols, Knowledge Worker
My Objective is to Help You Achieve Yours
âAssistance at a Distanceâ?SM
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–
Richard S. MarkenÂ
“The childhood of the human race is far from over. We have a long way to go before most people will understand that what they do for others is just as important to their well-being as what they do for themselves.” – William T. Powers
–
Richard S. MarkenÂ
“The childhood of the human race is far from over. We
have a long way to go before most people will understand that what they do for
others is just as important to their well-being as what they do for
themselves.” – William T. Powers