Geology Reference
In-Depth Information
In this example, there are only solid arrows. This means that if my perceptions become
distorted, my paranoia grows, which then feeds back to increase my distorted percep-
tions, and so on. The result is that both paranoia and distorted perceptions increase
without limit. This is a classical 'vicious' cycle, since the system has no tendency for
self-regulation. Imagine that my distorted perceptions cause me such distress that I de-
cide to talk about my situation with a close friend, or I might choose to see a therapist.
Either way, if the help is successful in reducing my distorted perceptions, my paranoia
will be reduced, and this will have the effect of reducing my distorted perceptions. Now
the change is in the opposite direction—instead of an unlimited increase, we now have a
potentially unlimited decrease—a 'virtuous cycle' that leads me into increasing levels of
sanity and well-being. Notice that there is no emergent self-regulation in positive feed-
back; there is only constant change, either towards more and more, or towards less and
less.
One technically inappropriate—but nonetheless effective—way of remembering how
negative and positive feedbacks behave is to imagine that a system's sign reflects its
at-
titude
to change. A system in negative feedback, when presented with change, is 'neg-
ative' to it, preferring instead to stay where it is. A system in positive feedback, on the
other hand, loves change, and is hugely 'positive' towards it. There is a simple rule of
thumb that we will find very useful for deciding if a feedback loop is in negative or pos-
itive feedback: simply count the number of inverse couplings, that is, dashed arrows. If
there is an odd number, the feedback is negative, if there is an even number, or none at
all, then the feedback is positive.
In fact, neither negative nor positive feedback can work without sensors that detect
tiny deviations from a set point that are amplified before the signal is fed back into the
original component. In Gaia, much of the amplification comes about due to the amazing
ability that all living beings have for exponential growth. A classic example comes from
the world of bacteria, in which the unrestrained divisions of a small initial population
would in a matter of days generate so many new cells that their mass would equal that of
the Earth. In Gaia the exquisitely delicate receptivity of living beings to their surround-
ings acts as an environmental sensor for the planet as a whole. Systems theorists usually
denote an amplifier by means of an inverted triangle, where the ingoing arrow denotes
the input signal, and the outgoing arrow the amplified output
(Figure 10)
