[From Rick Marken (931213.1000)]
Avery Andrews (931212.) --
PCT says that control will be easier to achieve if the controller has
the right perceptions - figuring out what these are is not necessarily
so easy.
Me:
What more can one say? Beautiful.
Avery Andrews (931213.1047) --
Of course the first bit of this was just cribbed off David
Chapman: `deciding what to do is easy when you know what's in
front of you'
Bill Powers (931213.0930 MST) --
David Chapman's saying is much too facile and egocentric for my
taste.
Mine too. Although Avery may have cribbed off Chapman, the result
("PCT says that control will be easier to achieve if the controller
has the right perceptions's") has (for me) a meaning that is
precisely the opposite of Chapman's -- and much deeper. Chapman's
statement (as you point out) suggests that the way we perceive can
"guide" what we do. Avery's crib does not imply that perceptions
"guide" -- it suggests that the main problem for the behavior model-
ler (roboticist or life scientist) is selecting the "right"
perceptual functions -- because the outputs of those functions are
what are controlled. I took the word "easier" in Avery's quote to
mean that you can eliminate all the inverse kinematic complexities
from your control model if you can determine all the perceptual
variables involved in the control process being modelled (as well
as the structural (hierarchical?) relationships between them).
The essential -- crucial -- difference between Chapman and Avery
(now that I look carefully) is that Chapman talks about "deciding
what to do" where Avery talks about "control". "Deciding what to
do" suggests (to me) "selecting an output". So I read Chapman as
saying "output selection is facilitated by perception (knowing
what's in front of you)". Avery is saying that control involves the
control of perception; modelling control requires discovering the
right" perceptions -- ie. the perceptual functions that provide
perceptual signals that, when controlled, result in "observable
behavior" that matches what the modeller wants to see.
The little difference between Avery's statement and the Chapman
statement from which it is cribbed reflect (for me) the
ESSENTIAL difference between PCT and conventional approaches to
understanding behavior.
Yeah Avery.
Yeah Bill.
Best
Rick