[Martin Taylor 2010.07.12.10.17]
[From Rick Marken (2010.07.08.2210)]
Martin Taylor (2010.07.05.00.05)--
In particular, since most perceptual pathways have much higher bandwidths than
the muscular part of the output pathway, if the perceptual bandwidths are
under study, it is often impractical to have feedback through the external
environment (which means that tracking methods cannot be used). The feedback
pathway must, in those cases, be internal (in imagination), and not visible
to the experimenter.But if the feedback path exists only in imagination how can the
subject control the variable that the subject has been instructed to
control? In fact, in all experiments, there is always an overt
response (like a button press) that affects the state of the
controlled variable. The output may occur after a lot of imagination,
but it occurs and that's how the experimenter (and the subject!) can
see that the variable the subject was instructed to control is,
indeed, under control.
The button response does not, and cannot, affect the state of the controlled variable, if that variable is the relationship between which interval the subject perceived to contain the tone and the numerical label of that interval, at least not if the subject is a normal healthy person.
I've been puzzling as to how, after so many years, you and I can have such different views of control in imagination, and why your view now seems so different from your view some years ago (as I remember it) when you were talking about the control involved in finding (I think) the word to fit in a crossword -- or something similar. At that time, your approach was to vary, in imagination, the possible words until one fit the clue and the space. That is exactly what I have proposed and you dismiss for answering the question of which interval contained a signal. You dismiss it on the grounds that control in imagination allows any answer to be made to fit.
I think I have found the answer to my puzzle. It is that we have been verbally conflating two different things. Control IN imagination depends on, but is different from control OF imagination.
Control OF imagination permits one to imagine anything that will satisfy some reference value. It is free. You can imagine yourself lying on a tropical beach, or wandering among the moons of Jupiter, or that peace has descended upon the world. The outer environment provides no constraints, and there are no obvious degrees of freedom limitations. If you want a particular imagined perception, and you are able to generate it, you can have it.
Control IN imagination is different. When one controls IN imagination, one is using the ability to create arbitrary perceptions, and using the created perception as one of the inputs to the perceptual input function of some other control system -- call it the system that controls perception X. In order for the X control system to achieve its reference value, the imagined perception must take on a value that works with the other inputs to the X perceptual input function to produce the X reference value for the X perception.
Control IN imagination is constrained. If the other input(s) to the X perceptual input function come from the outer world, the imagined input to the X perceptual input function must take on some specific value (or belong to a set of specific values) if the X control unit is to have zero error. The X control system output varies the imagined perception to work with the other inputs to its perceptual input function to reduce its error value in the same way that a control system in a tracking study varies the movements of a joystick to work with the disturbance in reducing the tracking error. The tracking control system varies the reference value supplied to the top of a hierarchy of lower-level control systems that eventually result in muscular output. In the same way, the X control system varies the reference value to a control OF imagination system to produce varying imagined perceptions.
Let's take the example of the experiment in which a subject listens to four noise bursts, in one of which is embedded a 500 Hz tone. But let's not ask the subject to report to the experimenter which interval it was. Let's just ask the subject to satisfy herself that she would be able to report to the experimenter if the experimenter asks. To make this into an experiment, let's say the experimenter does ask, but only after a small proportion of the trials, and then only about the trial before the one just completed. So, On trials 1..4, say, the subject just keeps silent, but on trial 5 the experimenter asks "Which interval was it on trial 4?".
In that experiment, you (Rick) would presumably argue that the subject could never provide the answer, since on trial 4 the subject had no button to push, no vocalization to hear, no externally detectable sign at all as to which interval had the tone. I would argue that on each trial the subject controlled IN imagination by varying the imagined answer ["2","1", "3" -- yes, that's right, "3"], and remembering "3" in case the experimenter asked after the following trial. The generation of the answer is, to me, entirely distinct from the dialogue with the experimenter.
In this example, the imagination "3" is freely generated, without constraint. That's control OF imagination. But no imagined perception other than "3" matches the externally supplied input to the relationship control system. That control IN imagination is as constrained as is any physically observable tracking output. Only when something in the external environment, such as the dialogue with the experimenter, depends on that imagination does the constrained imagination become a reference value for some output hierarchy of control systems.
The output part of the network of influences would be exactly the same as it would have been had the experimenter asked "Think of a number between 1 and 4, and tell me what number you thought of". What the subject told the experimenter in that case would be the result of control OF imagination. What the subject tells the experimenter in the actual experiment is still the result of control OF imagination, but in the experiment, control OF imagination is constrained by the control IN imagination of the relationship perception. The difference is just the same as would be the difference between an experimenter saying "move the joystick to some place you want it" and "move the joystick until the cursor is level with the target". Both tasks use the same output hierarchy, but in one case the output value is unconstrained (from the experimenter's viewpoint), whereas in the other it is constrained by the subject's willingness to do the task and by the location of the target.
All of that is a longwinded way of saying that we have been in the habit of just saying "control in imagination" to represent two very different things, which I have here labelled "control OF imagination" and "control IN imagination".
Martin
PS. I'm away again for about a week. I may access e-mail in that time, but I thought it better to post this before I left.