(This is Part 3 of a continuing series. Go back to Part 2.)
A knowledge of feedback loops can be extremely helpful, whether personally or organizationally. Let's see how:
Feedback loops were first discussed theoretically in the cybernetics revolution, initiated by Claude Shannon and his theory of information in the 1940's and now an integral part of network theory, complexity theory, nonlinear dynamics, ecology studies and many other areas.
What is a feedback loop? It's simply where the output of some process or system is fed back into the system as a partial input, modifying the process.
An example is the feedback used in jetliners to assist the pilot when bringing the plane in for a landing. It can be done in various computerized ways, but the way it was first done is an easy way to understand it.
When coming in for a landing, a plane is placed by the control tower on a glidepath, which is an electronic path in the sky which the plane follows to guide it in until it reaches touchdown.
If the plane deviates to the left from its glidepath, for instance, the pilot hears a certain sound in her earphones or on her indicators that lets her know that the plane has deviated to the left. The pilot then adjusts the plane until it's back on the glidepath.
Similarly, if the plane deviates to the right, or if its descent is too fast or too slow, the pilot will hear other sounds or see other indications that these things are happening, and she can then adjust the airplane accordingly, until it's back on the glidepath.
This is an example of negative or self-regulating feedback. That is, the feedback serves the function of regulating some process, and it does so by sending "negative" signals when the process is deviating from the desired goal.
Another example of negative feedback is the humble thermostat on the wall. The thermostat contains a sensor that measures the temperature of the room. If the room temperature is below the desired temperature (it's "deviating" downward), the thermostat sends a signal to the heater to increase the heat.
On the other hand, if the room temperature is above the desired temperature (it's "deviating" upward), the thermostat sends a signal to the heater to decrease the heat. In this way, the thermostat regulates the temperature around the desired point.
Now it turns out that this process is used extensively in nature as a mechanism to stabilize various systems. For instance, your body is constantly monitoring the blood sugar level in your blood. If it gets too low, the pituitary gland sends out signals to the pancreas and other organs to increase the blood sugar. Conversely, if the blood sugar gets too high, the pituitary sends out signals to raise the blood sugar.
In similar fashion, the body is constantly regulating the levels of various hormones, minerals, neuro-transmitters and thousands of other things to maintain its homeostasis, that is, its state of internal stability.
These various interlocking systems of process and regulation form a self-maintaining network. One of the characteristics of a network, whether neurons in the brain, organs in the body, or molecule chains in an ecosystem, are these interlocking negative feedback loops that maintain the homeostasis of the system.
Notice that these are called negative or self-regulating feedback loops. There is another type, known as positive or self-reinforcing feedback loops. A positive feedback loop reinforces a particular process instead of regulating it.
(This is the end of Part 3. Go to Part 4.)
—jim sloman, 12/2/02 for 1/8/03
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