[From Rick Marken (2014.02.19.1330)]
···
At long last here are my answers to the questions on Chapter 2 of LCS III. Feel free to continue discussing this chapter as long as you like. I’ll distribute the “Study Guide” for the next chapter – Chapter 3 – shortly.
1a. What do you think is the point of the first demo? What is
illustrated by the fact that you can control different aspects of the
display?
For me, the main point of the first demo is that we control perceptions of variable aspects of the environment. In the “Choose Control” the controller can pick one of three aspects of the same physical display and control it. What you actually do – in terms of the observed actions that are used to control the perception-- depends on which perceived aspect of the display you chose to control. That’s because what constitutes a disturbance to be resisted by those actions depends on what perceptual aspect of the world is being controlled. So the apparent effect of the external environment (disturbances) on behavior (actions that oppose disturbances) depends completely on what perceptual aspect of the work is under control. This demonstration illustrates the central insight of PCT and shows what distinguishes PCT from all other version of control theory that have been proposed as explanations of behavior. It shows that behavior is the control of perception, not of objective events in the world. So understanding behavior, from a PCT perspective, is a matter of understanding what perceptions are under control. Only when that is known – only when we know what perception(s) a system is controlling – can we start trying to figure out how it controls those perception.
- The section of Chapter 2 on The Input Function is the most
important section in the chapter for modelers. Why?
Because it is the input function that defines what perceptual aspect of physical reality is under control. In the “Choose Control” demo, the difference between controlling the shape, position or orientation of the object in the display is the difference in the input function around which thew control system is organized. The input function corresponds to neural networks in the organism that presumably transform the sensory input from the physical display into a neural current (see Premises in B:CP) that represent the state of the perceptual variable computed by the input function: for example, one input function that takes the sensed display as input and puts out a neural current whose varying magnitude corresponds to the varying orientation of the object in the display. Understanding how these input functions work should be the focus of studies of the neurophysiology of perception. Indeed, PCT suggests that the really important (and difficult) neurophysiological work that is aimed at getting an understanding of the neurophysiological basis of behavior will be research aimed at understanding how organisms perceive (how their input functions work) not so much on how they produce actions (output functions). Some recent research pertinent to this point is described in the this paper:
https://dl.dropboxusercontent.com/u/31298693/Hierarchical%20Control.pdf
The research shows, again, that what living control systems (people in this case) control is perceptions of the reality in their environment; the environment described by the models of physics and chemistry. In the “Hierarchy” paper we show what is demonstrated in the" Choose Control"; that people can control different perceptual aspects of the same reality. The “Hierarchy” paper just goes on to show (by presenting “reality” at different frame rates) that the different perceptual aspects of reality that are controlled in this experiment are hierarchically related.
The fact that the perceptions we control seem to be hierarchically related relates to David’s first question:
What levels of perception are needed to perform the task of chapter
2? Recall that a display changes in three ways–left/right position, shape
(round/nonround), and axis orientation (pointing towards you/not towardsyou). Don’t forget the levels of perception needed to understand and follow
the task instructions.
The answer to this question (as well as several other of David’s questions) requires knowledge of aspects of PCT that have not been discussed yet (Or are not discussed at all) in LCS III. I think the specific levels of the hierarchy proposed in B:CP is one thing that is not discussed in LCS III. Bill was always asking people to view his proposals about the hierarchy as a source of hypotheses for PCT based research. We did use it as a source of our hypotheses about the relative levels of perceptual control in the Hierarchy paper described above. So I’m reluctant to say what levels of perception are represented by the different perceptions that can be controlled in the “Choose Control” demo. Indeed, I’m not sure these perceptions actually represent different levels of perception; they all seem like configuration type perceptions to me. Though position might be a relationship type perception because you control it relative to some other point on the screen (“next to” or “above”, for example, which are relationships between). Same with orientation; it might be a relationship perception since orientation implies a relationship to frame of reference. We could use the techniques described in the hierarchy paper to see if this hypothetical hierarchical relationship between these perceptions actually exists.
On Page 22, Bill says: "The only thing that changed was which aspect
you decided to pay attention to and hold constant." Where does this happen
in the PCT model?
Again, this is a question about an aspect of the PCT model that is not really discussed in LCS III. And it is not a very well understood aspect of the model because it has to do with consciousness. Attention seems to be about becoming aware of different parts of one’s perceptual world and awareness was described in B:CP as a consciousness phenomenon. How this process of shifting awareness works is not well understood by anyone; but at least in PCT we know that consciousness phenomena are different than control phenomena. Control is purposeful behavior, which can occur with or without consciousness.
Based on your answer to question 1, which aspect of the display do
you think a person should be able to control better and why?
Given my hypotheses about the type of perceptions controlled in the “Choose Control” demo I would say that shape should be easiest to control.
Consider Bill's statement on page 25: "A second way to find the
controlled variable is to look for the minimum correlation between the
disturbance and the aspect of the ball being influenced by the disturbance."
Can you explain this in terms of the properties of the correlation
statistic? (hint: what happens to the size of a correlation coefficient when
the range of one of the variables is restricted?)
Oops, this is not a result of restriction of range (which is a reduction in the size of the correlation between X and Y that results from looking at the correlation between X and Y for only a subrange (just as just the lower half of he range) of the X or Y variable. The low correlation between disturbance and “the aspect of the ball being influenced by the disturbance” which is the controlled perceptual variable (CV), results from the fact that the subject’s outputs are preventing the disturbance from moving the CV from it’s reference state. The range of the CV is being restricted by the actions of the system, not by the person computing the correlation coefficient. So the low correlation between disturbance and CV is a result of restriction of the range of the CV but this is quite different that the restriction of range that results in a reduced correlation coefficient. In the case of control, only the range of the CV is being “restricted” by the actions of the control system; in the statistical restriction of range case, both the range of both the X and Y variables is being restricted when you restrict the range of one variable (or the other).
From pages 27 to 35, Bill introduces the basic concept of a negative
feedback control system. On Page 28, he says: "It has to sense the variable
under control to know whether its magnitude is less than or greater than the
desired magnitude and of course the controller must affect the controlled
aspect so it can be brought closer to the desired value (which requires a
comparison). What order do you think is best for acquiring a new control
system using the three components of input, comparator and out functions?
Again, I think this is asking about something that is well outside the range of anything that has been dealt with in either LCS III or B:CP. It does sound like a good area for research though.
The addendum to chapter 2, from pages 35 through 40, has been
involved in our current discussion of Ashby and feedback versus feed
forward. I would simply like to direct you to a research project that Bill
and I did with adults which made use of the transfer function approach
rather than the modeling approach. Go to:
You are right that the addendum to chapter 2 is relevant to current discussions we’ve been having on CSGNet. It is particularly relevant to the discussion of “feedforward” and our perennial argument about whether the outputs of a control system are based on information about the disturbance. I’ll just let that section speak for itself.
Best
Rick
–
Richard S. Marken PhD
www.mindreadings.com
The only thing that will redeem mankind is cooperation.
– Bertrand Russell