PCT/Non-PCT Descriptions of Behavior

[From Rick Marken (950531.1230)]

Bruce Abbott (950530.1445 EST)]

After much fruitless debate, we end up with Bill's really excellent
description of hummingbirds at the feeder, intended to get across to me the
difference between a description consistent with a PCT approach and one that
is not. The subtle point of my comment to Rick on this description is that
it is not really so different from mine: mostly pure description of
external behavior, with some suggestions being offered about the variables
being controlled.

The PCT description is, indeed, not very different from yours. But I think
the difference is significant. It is not just the suggestions about the
variables being controlled that distinguishes a PCT from a non-PCT
description of behavior. What I think is most important about the PCT
description is that it points to the varying environmental circumstances
(disturbances) that should lead to variation in some result of action -- but
doesn't. Bill's description of hummingbird behavior included a description of
the changing circumstances that exist as the birds feed. For example:

the whole feeder is usually swinging gently in the wind and twisting
slightly around the axis of the supporting string.

What was not explicitly stated was the fact that these changing circumstances
should lead to changes in at least one result of the birds' actions -- the
distance between the bird and the feeder. One has to know that this is
true -- that a constant distance between a floating object (bird) and a
swinging object (feeder) is not expected. But it happens:

a constant distance is maintained between the beak and the feeding port

The description also suggests how a constant distance is maintained, viz. the
bird varies its actions approriately so that this result (constant distance)
occurs rather than some other result. The variation in action that produces
a constant distance is described as follows:

The head and body of the bird swing back and forth in space, and the
orientation of the bird moves in an arc around the feeder as it twists

Bill never used the term "controlled variable" in his description of
hummingbird behavior. Nor did he explicitly suggest that "distance from the
feeder" was a controlled variable. What he did was describe the _fact_ that a
constant distance is maintained despite the changing position of the feeder
(and the changing velocity of the wind). His description suggests that
distance is under control; that a constant result is maintained (controlled)
because it is being protected from the effects of changing circumstances
(disturbace) by the actions of the organism.

In the Naftigall description of fly landing there was no description of
constant results being maintained under changing circumstances; there were
just descriptions of different results of fly actions: approaching the
ceiling at a steep angle at 25 cm/sec, stretching out legs, legs absorbing
shock, legs adhering at point of contact, fly clinging to the ceiling, etc.
All these are, indeed, results of the fly's actions, just as the distance
from the feeder is a result of the bird's actions. But in the Naftigall
description there is no indication that the same result is produced under
changing circumstances. For example, there is no indication that the
angle of approach or speed of approach is the same despite changes in the
angle of the ceiling, the velocity of the wind, etc. Including this small
detail is the differnece between a useless non- PCT description into a useful
PCT description of behavior.

If I had taken the time to develop my description of the variables being
controlled by the fly as it lands (including how these variables are
protected from disturbance), it wouldn't have sounded so different from

This is true as long as you do, indeed, include a description of the
diturbances to the proposed controlled variable and (if possible) a
description of the actions that protect the variable from disturbance. What
is most important in PCT description of behavior is to show that some result
of an organisms actions should, but doesn't, vary. The description must
include observations of a varying disturbance (like the changing position of
the feeder) and of a result of actions (like distance from feeder) that is
protected from the effects of this disturbance .

Naftigall's description of fly landing cannot be made into a PCT description
just by suggesting that some of the results produced by the fly are
controlled variables. For example, it would not have helped if Naftigall had
suggested that angle of approach, speed, degree of leg stretch, etc. were
controlled variables. This would be mere speculation; no more convincing than
saying that any other result of the fly's action is a controlled variable.
For example, one result of a fly landing on my ceiling is me swating it.
There is no reason to rule out this result of the fly's actions (getting
swatted) as a possible controlled variable based on Naftigall's type of
description of fly landing.

A PCT description of behavior, by including descriptions of constant results
and the varying circumstances under which they are produed, provides a
reasonable basis for guessing that a variable is under control. The actual
variable under control is, of course, some perceptual measure, from the
organism's perspective, of the result that remains constant despite changing
circumstances. The PCT description of hummingbird behavior suggests that the
hummingbird is controlling (among other things) a perceptual representation
of its distance from the feeder. We can guess that this distance is a
controlled variable because the PCT description of behavior included what was
needed to make this a reasonable guess -- it included a description of the
fact that this distance remained stable under circumstances in which it would
not have been expected to do so.

The PCT description of behavior is a description of control.