[Martin Taylor 2009.03.20.14.32]
[From Bill Powers (2009.03.20.0818 MDT)]
[Martin Taylor 2009.03.19.05.28]
[From Rick Marken (2009.03.18.2030)]
The "open loop" part is the path between the physical lights and the perceptual input function of the "match answer to presentation" control loop.
Yes, that path is open-loop; it's the path that goes from IV to DV in all conventional experiments.
I guess you haven't looked at the diagram. The DV is not the input to the perceptual input function of the "Match answer to presentation" control loop. Here's the diagram again, in generic form, without all the irrelevant control loops.
As Martin points out, Rick has the "answer" output above confused with the S1 input to the perceptual function. But Martin has omitted the input from the actually produced "Answers" to the perceptual function: organisms do not simply compute (in imagination) the reference signal they should emit to achieve a particular result and then emit it; they also monitor and adjust the action to make sure that the result of sending this reference signal is in fact the perception -- that is, the spoken or written answer -- they have selected.
I can interpret this in at least three ways:
(1) That to determine the appropriate answer is a control process, varying the possible answers until one matches the category perception of the presentation.
(2) That there are control processes involved in producing output appropriate to the answer that matches the category perception of the presentation,
(3) That the perception that is controlled in the physical method of answering (button) is part of the perceptual input function to the matching process.
Since I don't know which, if any, of those you intend, here's my comment on all of them.
(1) Assumed to be true.
(2) Assumed to be true
(3) Unlikely but conceivable
I do have a problem with: "organisms do not simply compute (in imagination) the reference signal they should emit to achieve a particular result and then emit it; they also monitor and adjust the action to make sure that the result of sending this reference signal is in fact the perception -- that is, the spoken or written answer -- they have selected." This way of putting things seems to incorporate into a single control loop a variety of disparate functions and to make the controlled perception into a complex, rather than the scalar variable that we usually prefer to consider. There's nothing wrong with thinking about control of a complex variable (I don't mean one with "real" and "imaginary" parts in either the mathematical or the PCT sense of "real" and "imaginary"), and maybe we should, but so long as scalars work, Occam's Razor suggests we should continue to use them by preference.
In this situation, the response is more "fire and forget" than "continuous control". Yes, there is control, in that the subject can see the "fall of shot" (correctness of the button push) and use it to influence the choice of which button corresponds to which answer, or which answer to which perception. That seems to me to be a separate control system from the one that does the actual matching of the answer category to the category perception of the presentation.
Another problem I have is with the assertative mode, which suggests that you have indisputable knowledge of what organisms do or don't do: "Organisms do not ..." might be better stated as: "As I choose to model them, organisms do not..." Nothing in PCT argues that organisms do not compute in imagination the reference signal they should emit. How else can "fire and forget" systems, which alter their performance according to the results of earlier instances, determine where to aim to hit a particular target? "Last shot hit 20m left of where I aimed, so next time I have a target I will aim 20m further to its right". Is that not computing in imagination the reference signal that should be emitted to the gun layer for the next shot? What is the difference when it's not a gun but a button push that corresponds to an answer determined by control in imagination?
Therefore the higher system shown here is a closed-loop control system which controls the relationship between the perceived answer and the (observed) presentation. The presentation is not altered by the answer. Changing the presentation alone disturbs the relationship; the answer is adjusted to cancel this effect of the presentation and keep the perception of the relationship matching the reference condition.
Yes. That all goes on before the button-push action is initiated. The output should be the reference value for the button-push control system.
Since we have no information about just what this relationship is for the person in question, the analysis stops there.
I think we have reason to believe that the relationship is what the experimenter has requested that it be. In effect, the experimenter has performed "The Test for the Controlled Variable", even if he had no idea such a Test exists. He has determined that the subject can perceive the disturbing variable, created various disturbances (left-light, right-light) and shown that when the signal delay is sufficient, there is an almost perfect match between the button-push and the disturbance (output tracking the cursor disturbance in a tracking task). The Test says that somewhere inside the subject, there is a control system controlling for a match between the presentation and the answer. The only assumption necessary is that the subject is trying to control in the same way when the available information is insufficient as when it is sufficient. The reason it is sensible to believe this to be the case is that the data vary smoothly and consistently as the bip-delay changes, and more specifically that the rate of information gain is very tightly linear. If there were a break in the information gain rate, one might be led to suspect a change in the subject's control parameters or systems, but there isn't.
The reference signal is not an "interpretation" because an interpretation is a kind of perception; it is a specification for the state of the perceptual signal.
Yes, I see the "answer" as a reference signal for the system that controls the perception of which button is being pushed.
But my question was about data; what data is it that tells you about the open loop channel capacity of the subject.
You keep changing the topic, talking about "the open loop channel capacity of the subject". You are the only one in this discussion to consider this to be a possible topic of conversation, since nobody else (so far as I know) considers the concept to have any meaning.
You two guys are clearly irritated with each other and letting it show, and you aren't trying very sincerely to understand each other or explain things to each other.
I dispute that. I was frustrated by my inability to get Rick to do one of three things: (1) Understand what I am trying to say; (2) Explain to me what it is he doesn't understand; or (3) Explain to me what is wrong with something I have said. But I'm not frustrated any more, since Rick said it was now clear, and I choose to believe he was serious when he said that. For myself, I had been almost desperately trying to understand what he is trying to get at, beyond that humans are control systems. I've tried many different ways to ask, but with zero success.
The Schouten experiment, in my opinion, is clever and interesting but leaves too many assumptions unjustified (as it stands) to serve as the basis for any important conclusions. Martin may know, but the rest of us don't, just how the time of actual pressing of the button relates to the timing of the bips, or in English, beeps.
I take a "bip" to be a short "beep". Since I made the effort to find Schouten's paper, I do now know how the time of the button press relates to the bips. The distribution is what one might call "by eye Gaussian" with a standard deviation averaged over all subjects that depends on the actual bip time (by the way, the bip sequence was 3 20 msec bips separated by 75 msec). Scouten mentions that the changes in the histograms of button-press times as a function of bip time was different for different subjects, so one should not take the averaged data as any more than suggestive. For what it's worth, the by-eye SD in the mid-range of bip delays combining the data from all subjects was about 20 msec, but wider for very short and very long delays, so for any individual subject, the variation must be less than that. Schouten mentions that only one subject was precise at very short delays, and only a few were precise at the long delays, so your "grain of salt" in considering the SD I mentioned should be rather large.
I don't think anyone knows how long before the button is actually pressed enough to close a contact the decision to press it is made, or how long it takes after the light comes on for that decision process to commence, or how long it takes, once it commences, to try different answers and find the one that generates the right relationship.
Right. But unless there is reason to believe these things change as a function of bip time, they don't influence the interpretation of the results in respect of the behaviour or capacity of the "red pathway".
We don't know how the perceptual signal changes with time after a light comes on, or for that matter how long it takes for the filament to warm enough after the circuit is closed to generate visible light. As in many psychological experiments, the mere physics of what is going on (as well as the neurology) is oversimplified if it is noticed at all.
The only one of these that matters is the first. The experiment was intended to test how the perceptual signal changes after the light comes on. Schouten's original interpretation was the same as what Bill proposed in an earlier message, an exponential rise to some asymptote. What I showed Schouten (and what I published) was to show that his data implied that the subject was gaining information about the presentation at a steady uniform rate for at least the first 100-150 msec.
I'm prejudiced against information theory, because so far I haven't seen anything you can discover by using it that you can't discover some other way, except of course for the final conversion, through the log to the base two, into units of bits.
As a carpenter with a saw, hammer, and chisel might be prejudiced against screwdrivers, because one can certainly turn a screw with a chisel, and the carpenter could probably make nice furniture without a screwdriver. When I was in high school in Toronto, one of the exam question was supposed to be answered by complex trigonometric calculations. I did it by calculus, which I had learned in Scotland, but I was told that was unfair, and got no marks for the question. You certainly can solve a lot of problems with the tools you know, but if better tools for a particular job are available you don't need to. Unfortunately, it's very hard to know when a particular tool is likely to be better until you have some familiarity with it. Screwdrivers don't make very good chisels, though they have sometimes been used for that purpose!
The old-timers in electrical engineering liked to speak of amplification and signal loss in units of decibels, but I never found that very helpful either. I wouldn't really mind changing my opinion about information theory, but just being told that I'm ignorant doesn't provide the kind of motivation that gets me going.
Is that all you have gathered from my attempts at explanation? I must be an awful lot worse at communicating than I had imagined. Let's just try one comment, which applies to both decibels and information: both can be useful because they make certain operations into simple additions. Put a 10db gain amplifier in series with a 3 db loss, and you have a 7 db gain. Certainly you can get the result by multiplication, but quite often addition is easier. For information, if you get n bits from observing 1 second of a signal, and the next second is independent of the first, you get 2n bits by observing 2 seconds. That's the situation in the Schouten study.
As I recall, this whole subject arose either because of or after I made some comments about people bringing old ideas and accomplishments with them into PCT. Martin cited the Schouten experiment as an example of valid information obtained from traditional (or at least non-PCT) approaches. Apparently Martin hopes that something of value can be retained out of the pre-PCT history of science.
Hopes? No, I neither hope that it does or hope that it does not. There's no vested interest, just an understanding that everything I know about PCT argues that there is a lot of value to be gathered from the last couple of centuries of experiments in psychology. Of course there's a lot of junk. The question is to determine what is and what is not junk. I think that in this thread I have demonstrated that at least pretty well all detection and discrimination experiments done in the conventional way have produced results that can be used in PCT-science.
Rick argues against Martin not because he understands what Martin says and sees what it wrong with it, but because he wants Martin to be wrong about the value of pre-PCT science. Of course I'm only reporting one bystander's subjective impressions here, but it doesn't seem to me that anyone is really interested in FINDING OUT what the truth of the matter is.
Well, let's just ask the lurkers.
IS anyone really interested in finding out what the truth of the matter is? I made a start in [Martin Taylor 2009.02.17.11.23] at suggesting a catalogue of conditions under which non-PCT psychological results might be valid and useful. Nobody has commented on it, though I know it got sent out to the list. The "generic" diagram on which Bill and Rick were commenting comes from that message, which had the subject line "Measurement of functional components".