Question About Feedback Functions

[rsmarken]

@bnhpct

@rsmarken

The CV – the output of the perceptual function – is a crucial part the feedback path! The environment and the sensory effects thereof are also in the feedback path

@rsmarken

The CV is a perceptoin and, thus, not in the environment outside the “skin” of the organism. But, as I have shown above in the “What is Size” demo, it IS most DEFINITELY part of the feedback function. And, of course, it can be objectively determined by some version of the Test for the CV. I think you have been confused by the fact that we often call the feedback function the “environmental” feedback function.

Perhaps you can show how there are no contradictions here. I can’t. (The figure is from B:CP p. 286.)

I think this is the toughest thing for people to understand about PCT and the toughest thing to explain (for me anyway). The thing that makes it tough is that the variable qi, which is shown as being out in the environment, is the SAME variable as p, which is inside the system. Both qi and p are a function of environmental variables.

For example, in the “What is size” demo, when you are controlling the area enclosed by the rectangular lines, qi = h * w and p = h* w, where h is the height and w is the width of the rectangle. Indeed, qi = h * w because p = h * w. And p = h * w because you are controlling the area of the rectangle enclosed by the lines.

If you decide to control the perimeter surrounding rather than the area enclosed by the retangular lines then qi = 2*(h+w) and p = 2*(h+w). And again qi = 2*(h+w) because p = 2*(h+w). And p = 2*(h+w) becuase you are now controlling the perimeter surrounding rather than the area enclosed by the retangular lines.

Of course, qo and p are not exactly the same due to noise in the perceptual neural net that computes p, so p = qi + noise. But this noise represents only about 2% of the variance in p so it has little effect on evaluating the accuracy of control models. The main effect on the accuracy of control models is how accurately you have identified qi, which requires correctly identifying the controlled perceptual variable, p.

This is obvious in the “What is size” demo. A model of the controlling done in that task will be highly accurate if the controlled variable in the model – qi-- is identified correctly. That is, qi is correctly identified as hw when area is being controlled and as 2(h+w) when perimeter is being controlled. Also, because the qis, and, thus, the feedback functions, are different in the area and perimeter control cases (even though the connection between mouse and display is the same in both cases) the modeler will have to take that into account in modeling the behavior in the “What is Size” task.

I’m developing a spreadsheet model of the behavior in the “What is Size” task and I’d be happy to send it to you if this is still not clear.