[From Bruce Abbott (941211.1510 EST)]
Bill, I've just received your post (941210.13) replying to "Who's On First";
I'd like to take a little time to think about it before continuing along that
line. However, here's something I've been bothered by; perhaps you can shed
some light on it.
I've quickly learned to perform the one-dimensional cursor tracking task, and
am doing quite well correcting for disturbances when suddenly the computer
reverses the effect of the mouse. At the moment, the cursor is below
reference and I am pushing the mouse forward to correct, only to discover that
the cursor is getting further and further below reference. So I start pulling
the mouse backward and viola!, the cursor begins to move upward toward the
reference level. In a short time I have the cursor back under control.
Questions: What has changed (in me)? How? What comparison was made in order
to determine that something was "wrong?" What comparison was made afterword
to determine that things were now "right" again? Was an "intrinsic" error
involved? Is learning involved? Reorganization?
This is a very real problem, which anyone who flys radio-controlled model
aircraft has experienced first hand. It is relatively easy to learn to push
the "stick" left to make the plane go left and right to make the plane go
right, when the plane is moving AWAY from you. As soon as you get the plane
turned around and heading TOWARD you, it is another matter entirely. All of a
sudden pushing left makes the plane (as seen by the pilot) go right and vice
versa! I've been flying radio-controlled gliders (8 foot wingspan) for about
fifteen years now and adjust to this reversal automatically, but I can tell
you it was no easy thing to learn! Fortunately I had some guys who were
willing to provide the training--and quickly take over when I got into
By the way, flying radio-control aircraft provides an excellent introduction
to PCT. The only way you can maintain control over the aircraft is via visual
feedback. Lose sight of the aircraft and you experience instant loss of
control, usually resulting in loss of the aircraft (either literally or in
terms of its structural integrity). In addition, the radio control system
makes use of "servos" to actuate the control surfaces of the aircraft. The
position of the control stick on the radio alters the position reference
signals of the servos, which then rotate until their actual angle matches the
reference. Thus the radio-aircraft unit is itself a set of (one-level)
perceptual control systems.
When you grab hold of the control stick, your lower-level control systems
begin setting the reference levels of yet another system, through which you
are able to construct another control loop from stick to aircraft-attitude to
visually-perceived aircraft attitude/position/velocity, which is then compared
with your own reference levels for same to generate stick-position outputs.