[Martin Taylor 960307 11:15]
G. Scott Graham (apparently Wed, 6 Mar 1996 21:45:49)
I am looking for a metaphor ro help me understand the concept of
positive feedback.
How about a nuclear fission explosion? Each split atom generates more than
one neutron that will cause another atom to split if it is captured, generating
more than one neutron that ....
Strictly speaking, this isn't positive feedback, since it isn't the same
atom that splits more and more, but it might be a reasonable metaphor.
It's hard to see positive feedback, since it always results either in an
explosion or in something going to zero or some limiting boundary value.
I am a therapist and certified addictions counelor.
...
I believe the concept of positive feedback holds merit for understanding
paradoxical interventions....
I don't know what "paradoxical interventions" are, but I do believe that
positive feedback is important in the reorganization of a control hierarchy.
Under most circumstances, all loops in a hierarchy will have negative or
near-zero gain. But any loop that has a feedback path through the environment
is vulnerable to changes in the characteristics of that environment (the
ground underfoot may actually be a near-invisible sheet of ice, for example,
and the control actions that would normally serve to keep one upright now
serve to accelerate a fall). In particular, some change in the environment
might lead to some loop gain going substantially positive, leading to an
"explosion" (e.g. temper tantrum).
As we mature, we are exposed to ever more varied environments, and the
reorganizations that have accompanied or followed cases of positive feedback
will have constructed a hierarchy that can cope with the different variations.
But some people will not have reorganized effectively, and will continue
to do actions that drive their perceptions away from the reference values.
They don't "know" how to act to get what they want. (I don't mean explicit
knowledge necessarily, but the "knowledge" implicit in the structure of
weights and functions in the hierarchy). Most of the time, they control
fine (they'd be dead if they didn't), but some particular environmental
change can set some loop(s) into a positive feedback condition, in which
the person does self-damaging actions. That environmental change might
be as slight as the sight of some specific object, or as great as being
lost in a foreign culture where one's ordinary means of social interaction
were taken as insults; it would be very specific to the person and the
environments.
Here's another metaphor, from the world of electronics. It might also be
relevant in therapy: a flip-flop. In a flip-flop, there are two important
signal values. When either is high, it tends to depress the other, and
when either is low, it tends to elevate the other. So if they are in a
neutral state, and signal A is pushed upward a little, it pushes B down
a little, which pushes A up some more, which... The end result is that A
gets to be as high is it can go, and B as low as it can go.
Flip-flops have external data sources. Now let's say that the source feeding
B gets data that would drive it upward, while A is trying to drive it
downward. If the data are strong enough, they will overwhelm the effect
of A, and push B up, driving A down, and the flip-flop gets locked into
the opposite configuration. This same effect can occur when there are more
than two signals that have this mutually inhibitory relationship; only one
of the set can be high at any one time. Might this have some relationship
to multiple-personality disorders?
Anyway, there aren't any "stable metaphors" for positive feedback, since
it's an inherently unstable condition.
Martin