[From Bill Powers (960206.1430 MST)]
I'll be off on a quick trip East for my father's birthday, starting
Thursday Feb. 8 and returning Monday, Feb. 12. He'll be 96.
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Martin Taylor 960206 12:20 --
In your usual description of a perfaction loop--a diagram--you show
one CEV that is affected by one disturbance input and one influence
from the output function of the perfactor. You recognize verbally
that there are many _physical_ influences that contribute, but
nevertheless the CEV has to be scalar, because the perceptual
variable derived from the function that defines the CEV is scalar.
Yes, you're right about that.
If we have a perceptual variable p that is an input- function i of some
set of environmental quantities x1 ..xn, we have p = i(x1..xn). Out of
the n variables, m are affected by action, so the environmental feedback
function works through variables x[1].. x[n-m], and the variables x[m]
..x[n] are the aggregate disturbance. On this much, we agree.
My preference is to characterize the perceptual input function in terms
of _all_ the input variables that affect it, leaving the distinction
between feedback variables and disturbances to be determined when the
effects of action on the environment are known. Two perfaction systems
having identical input functions with identical sets of x's as arguments
may use different actions to perfact the perception, which would change
the partitioning of the x's into f's and d's.
Your point, made several posts ago, that the effective environment has
to be defined relative to the perfacting system in question is still
valid. I merely point out that the output connections also have to be
taken into account. Two systems perfacting the same CEV are not
necessarily doing so through the same environmental variables, and what
is a disturbance to one system is not necessarily a disturbance to the
other.
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Best,
Bill P.