(This is Part 18 of a series. Go back to Part 17.)
All naturally-arising self-organizing networks maintain
homeostasis, that is, internal stability, through negative feedback systems. A negative feedback system, as discussed earlier, is one that helps to regulate the network.
An example is the blood sugar level in your body. If it gets too high the body brings it down and if it gets too low the body brings it up. The body normally maintains the blood sugar level within fairly narrow limits. It does the same thing with hormone levels, levels of CO2, neurotransmitters, blood PH, body temperature and countless other variables.
Another example might be the stock market. Under stable economic conditions, the market normally maintains a kind of homeostasis of its own, where up moves are followed by down moves and down moves are followed by up moves. When buyers have exhausted themselves then sellers take over. When sellers have exhausted themselves then buyers take over, in a naturally self-correcting process.
Another example might be the world ecology. All sorts of things are maintained within narrow limits by the global ecology, such as ocean salinity, atmospheric oxygen levels, predator-prey populations and countless other self-correcting negative-feedback systems.
However, network theory/chaos theory also looks at situations where a "negative" feedback process can become overwhelmed and give rise to a "positive," or runaway, feedback process.
An example of a break-away feedback process in an organic network is the disease of cancer. Normally, the body maintains a negative-feedback process (the immune system) for identifying, killing and excreting cancer cells arising in the body.
However, if toxic pollution in the body rises beyond a certain point the immune system begins breaking down. Most often, this happens from a diet too high in fats, sugar, salt, animal proteins, synthetic foods, etc., but the immune system can also be severely damaged by such things as chemotherapy, radiation, viruses, environmental pollutants and so on.
As the process of toxification proceeds, the functioning of the "negative," stabilizing feedback process—the immune system—diminishes, and a "positive" feedback process—the growth of cancer cells—can begin to accelerate.
What "positive feedback process" means is that the process of increase becomes self-reinforcing: For instance, cancer cells, freed from the limitations of ordinary cells, draw to themselves new blood vessels to nourish them, which in turn increases the number of cancer cells and so on. As the negative feedback system falters, the positive feedback system—the colony of cancer cells—takes over and begins to spiral upward.
The same thing can happen in the economic sphere. Normally the stock market, or the dollar on foreign-exchange markets, trades within a range of 10-20%. Natural self-correcting processes act to regulate the price.
For instance, if the dollar rises too high our exports become more expensive; hence fewer exports are bought by other countries and so the dollar comes down. On the other hand, if the dollar goes lower our exports become more inexpensive and more of them are bought, resulting in a rise of the dollar. Within limits, a self-regulating process.
The same is true of the stock market; it's normally self-regulating. When it gets too low, buyers step in, attracted by the bargains. When it gets too high sellers step in, wanting to lock in profits. This is a natural process of homeostasis, a stabilizing cycle.
However, as discussed above concerning cancer, under unusual circumstances self-regulating feedback systems can break down and new self-reinforcing (that is, positive feedback) systems can take their place:
(This is the end of Part 18. Go to Part 19.)
—jim sloman, 1.25.03 for 4.25.03
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