Servos and Behavior

[From Gary Cziko 941212.1655 GMT]

Bruce Abbott (941211.1510 EST) said:

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.

Dag Forssell's demonstration of how these servos work a few years ago at a
CSG meeting provided what I found to be very helpful demonstration of basic
PCT principles and I have been playing with my own ever since. And if
Bruce understands how they work (as I am sure he does), he should also see
how learning (actually reorganization) does not involve the selection of
behaviors but rather the selection of reference signals sent to lower-order
control systems (or trajectories of reference signals--what some people
call homeo rhesis).

So it is reference levels that are "selected" by their consequences (the
magnitude of the reference signal (voltage?) sent to the servo, NOT the
output (current) sent to the motor. The latter must vary (and does) in
order that the perceived angle of the rotor matches the reference signal
under conditions involving unpredictable disturbances.

Does this make sense, Bruce? By the way, where are you in Indiana? You
can't be too far from me here in East Central Illinois and I (and maybe
Clark McPhail, too) would be happy to have you visit our campus and play
with our PCT toys.--Gary